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1005.3619	c	we have derived fe abundances via an ew analysis of and lines in high - resolution and moderate - s / n spectra of 16 ms dwarfs in the pleiades open cluster . the [ /h ] abundances increase dramatically relative to [ /h ] at @xmath0 below 5400 k , with the difference reaching over 0.8 dex in the coolest stars . this behavior is akin to what is seen in m34 , the hyades , and the uma moving group . comparison of the @xmath2 abundance patterns in the pleiades and hyades , as well as the [ o / h]@xmath41 abundances in the pleiades , hyades , and uma moving group , suggests that the trends may relax with age , though metallicity may yet prove to be a factor . abundances of cool dwarfs in additional open clusters or other stellar associations , especially those older than the hyades , are needed to determine if either age or metallicity are related to these anomalous abundances . the [ /h ] abundances are also higher in pleiads below 5400 k , but they show no evidence of an increase with decreasing @xmath0 . the inability to attribute the high [ /h ] abundances of the cool stars to the over - excitation effects illustrates the difficulty of quantifying this phenomenon . with lines of exceptionally high excitation potential such as the triplet , the over - excitation effect is clearly seen ( e.g. , * ? ? ? * ; * ? ? ? * ) , but for lines with excitation potentials @xmath70 ev , the effect is more difficult to pinpoint . our linelist includes transitions ranging in excitation potential from 2.18 to 5.10 ev , but for the individual pleiades stars , no increase in the line - by - line abundances as a function of excitation potential , like that seen in abundances of cool hyades dwarfs ( 1.83 ev @xmath71 4.42 ev ; * ? ? ? * ) , is evident ( figure 4 ) . line - to - line sensitivities to the over - excitation / ionization effects have yet to be clearly delineated , and it needs to be determined if there is an excitation potential threshold above which the abundances derived from these lines become enhanced by these effects . similarly , it needs to be determined if there is an excitation potential threshold _ below _ which the opposite occurs , the abundances derived from the low - excitation lines are lower due to these effects . such behavior would be expected if the overabundances of high - excitation ( singly ionized ) lines are due to the overpopulation of high - excitation ( singly ionized ) electronic states at the expense of depopulating low - excitation states . whether or not the over - excitation effects impact the spectroscopic derivation of stellar parameters ( @xmath0 , @xmath27 , and @xmath28 ) , an approach not adopted here , also needs to be determined . future investigations of these effects will require high - quality high - resolution spectroscopy so that accurate line - by - line abundances can be derived , even from features of just a few m in strength . a strong correlation between the @xmath2 and [ o / h]@xmath41 abundances of the pleiades dwarfs is evident in figure 2 , suggesting that the over - excitation / ionization effects share a common cause or origin . chromospheric emission and photospheric spots have been shown to be promising culprits , but to this point , the data are inconclusive . whereas strong correlations between the pleiades @xmath2 and chromospheric emission indicators and their residuals exist , they do not exist between [ o / h]@xmath41 and chromospheric emission . these contradictory results complicate the interpretation of the observed over - excitation / ionization effects and will have to be addressed by future studies . also , comparing abundances and chromospheric emission indicators measured using different spectra may not provide an accurate test of a true correlation because of potential temporal changes in chromospheric activity levels . future investigations into the over - excitation / ionization effects in cool open cluster dwarfs should make every effort to derive chromospheric activity levels from the same spectra so that any possible relation between the two can be more definitively delineated . determining the influence of photospheric spots on abundance derivations is more arduous . multicomponent model atmospheres- simulating photospheres with different areal coverages of hot , cool , and quiescent spots- have been shown to able to reproduce the measured ews of the triplet in a sample of hyades stars , but , while such exercises are useful and demonstrate the plausibility of the photospheric spot hypothesis , the results are only suggestive . observationally , a simultaneous photometric and spectroscopic monitoring program could be used to identify any correlated changes in spot coverage and spectral line strengths . such observational constraints would be helpful to determine if spotted photospheres affect high - resolution abundance derivations . despite the challenges , the possible connection between spots , over - excitation / ionization effects , and pre - ms li depletion should provide sufficient motivation for future efforts . a final conclusion that can be drawn from this study is that those carrying out spectroscopic abundance analyses of open clusters should heed caution when their samples include cool dwarfs , particularly those with @xmath0 @xmath1 k. including the abundances of these stars may skew cluster mean abundances . a similar caution may be needed for those studying cool ms dwarfs in the disk field , as well . further investigations into the sensitivity of the over - excitation / ionization effects to excitation potential , first ionization potential , stellar age , and stellar metallicity are needed in order to identify the extent and ubiquity of these effects . gratefully acknowledges her support for summer research from the national science foundation through their research experience for undergraduates program at cerro tololo inter - american observatory ( grant ast-0647604 ) . a.l.p . also thanks the c.v . starr - middlebury school in latin america for additional support . s.c.s . is grateful for support provided by the noao leo goldberg fellowship ; noao is operated by the association of universities for research astronomy , inc . , under a cooperative agreement with the national science foundation . j.r.k . gratefully acknowledges support for this work by grants ast 00 - 86576 and ast 02 - 39518 to j.r.k . from the national science foundation and by a generous grant from the charles curry foundation to clemson university . allende prieto , c. , barklem , p. s. , lambert , d. l. , & cunha , k. 2004 , , 420 , 183 an , d. , terndrup , d. m. , pinsonneault , m. h. , paulson , d. b. , hanson , r. b. , & stauffer , j. r. 2007 , , 655 , 233 asplund , m. 2005 , , 43 , 481 boesgaard , a. m. 1989 , , 336 , 798 boesgaard , a. m. , budge , k. g. , & ramsay , m. e. 1988 , , 327 , 389 boesgaard , a. m. & friel , e. d. 1990 , , 351 , 467 castelli , f. & kurucz , r. l. 2004 , 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l117 schuler , s. c. , king , j. r. , terndrup , d. m. , pinsonneault , m. h. , murray , n. , & hobbs , l. m. 2006b , , 636 , 432 shen , z .- x . , jones , b. , lin , d. n. c. , liu , x .- w . , & li , s .- l . 2005 , , 635 , 608 shen , z .- x . , liu , x .- w . , zhang , h .- w . , jones , b. , & lin , d. n. c. 2007 , , 660 , 712 sneden , c. 1973 , , 184 , 839 soderblom , d. r. , jones , b. f. , balachandran , s. , stauffer , j. r. , duncan , d. k. , fedele , s. b. , & hudon , j. d. 1993 , , 106 , 1059 takeda , y. 2003 , , 402 , 343 yong , d. , lambert , d. l. , allende prieto , c. , & paulson , d. b. 2004 , , 603 , 697 @xmath72 & & 0.65 & & 5715 & & 4.55 & & 0.96 + @xmath73 & & 0.75 & & 5339 & & 4.61 & & 0.58 + @xmath74 & & 0.65 & & 5715 & & 4.55 & & 0.96 + @xmath75 & & 0.84 & & 5048 & & 4.64 & & 0.30 + @xmath76 & & 0.89 & & 4899 & & 4.66 & & 0.16 + @xmath77 & & 0.75 & & 5373 & & 4.60 & & 0.61 + @xmath78 & & 0.73 & & 5407 & & 4.60 & & 0.65 + @xmath79 & & 0.82 & & 5098 & & 4.64 & & 0.35 + @xmath80 & & 0.73 & & 5407 & & 4.60 & & 0.65 + @xmath81 & & 0.81 & & 5142 & & 4.63 & & 0.39 + @xmath82 & & 0.74 & & 5363 & & 4.61 & & 0.60 + @xmath83 & & 0.78 & & 5239 & & 4.62 & & 0.48 + @xmath84 & & 0.78 & & 5239 & & 4.62 & & 0.48 + @xmath85 & & 0.72 & & 5442 & & 4.59 & & 0.68 + @xmath86 & & 0.80 & & 5174 & & 4.63 & & 0.42 + @xmath87 & & 0.82 & & 5117 & & 4.64 & & 0.37 + @xmath88 & & 0.53 & & 6172 & & 4.48 & & 1.42 + @xmath89 & & & & 5777 & & 4.44 & & 1.38 + & & 5793.92 & & 4.22 & & -1.70 & & 33.9 & 7.52 & & 46.0 & 7.63 & & 37.0 & 7.59 & & 47.5 & 7.61 & & 45.4 & 7.56 & & 39.3 & 7.51 + & & 5856.10 & & 4.29 & & -1.64 & & 36.6 & 7.57 & & 42.1 & 7.56 & & 30.8 & 7.46 & & 47.8 & 7.62 & & 51.1 & 7.67 & & 43.0 & 7.59 + & & 5927.80 & & 4.65 & & -1.09 & & 45.7 & 7.52 & & 54.0 & 7.58 & & 41.5 & 7.46 & & 60.3 & 7.63 & & 63.9 & 7.67 & & 56.5 & 7.63 + & & 6089.57 & & 5.02 & & -0.94 & & 41.8 & 7.64 & & 47.1 & 7.63 & & 35.3 & 7.52 & & 49.5 & 7.64 & & 56.6 & 7.74 & & 43.0 & 7.57 + & & 6093.65 & & 4.61 & & -1.50 & & 32.0 & 7.63 & & 39.6 & 7.67 & & 30.4 & 7.60 & & 45.9 & 7.76 & & 42.5 & 7.69 & & 39.4 & 7.68 + & & 6096.67 & & 3.98 & & -1.93 & & 41.2 & 7.64 & & 52.8 & 7.75 & & 42.4 & 7.68 & & 52.9 & 7.70 & & 55.1 & 7.72 & & 49.2 & 7.69 + & & 6151.62 & & 2.18 & & -3.29 & & 52.5 & 7.45 & & 66.5 & 7.58 & & 53.6 & 7.50 & & 76.0 & 7.64 & & & & & 61.4 & 7.48 + & & 6165.36 & & 4.14 & & -1.47 & & 48.3 & 7.46 & & 58.3 & 7.56 & & 47.2 & 7.47 & & 58.1 & 7.49 & & 57.6 & 7.47 & & 53.0 & 7.46 + & & 6270.23 & & 2.86 & & -2.71 & & 56.2 & 7.59 & & 70.8 & 7.77 & & 57.6 & 7.67 & & 68.8 & 7.62 & & 75.3 & 7.69 & & & + & & 6627.56 & & 4.55 & & -1.68 & & 30.9 & 7.71 & & 30.6 & 7.59 & & 30.0 & 7.69 & & 37.0 & 7.69 & & 39.1 & 7.74 & & 36.6 & 7.73 + & & 6806.86 & & 2.73 & & -3.21 & & 36.4 & 7.57 & & 53.1 & 7.72 & & 37.8 & 7.60 & & & & & & & & 47.1 & 7.61 + & & 6839.84 & & 2.56 & & -3.45 & & 37.2 & 7.65 & & & & & 35.8 & 7.62 & & & & & 58.4 & 7.76 & & 38.5 & 7.48 + & & 6842.69 & & 4.64 & & -1.32 & & 41.8 & 7.64 & & & & & 43.5 & 7.68 & & & & & & & & 44.1 & 7.60 + & & 6857.25 & & 4.07 & & -2.15 & & 23.4 & 7.54 & & 35.0 & 7.66 & & 23.8 & 7.54 & & & & & 37.1 & 7.66 & & 28.5 & 7.52 + & & 6861.94 & & 2.42 & & -3.89 & & 21.5 & 7.61 & & & & & & & & & & & 42.5 & 7.69 & & 32.5 & 7.63 + & & 6862.50 & & 4.56 & & -1.57 & & 29.9 & 7.58 & & & & & & & & & & & 45.9 & 7.76 & & 40.2 & 7.69 + & & 7284.84 & & 4.14 & & -1.75 & & 38.8 & 7.51 & & & & & 46.0 & 7.66 & & & & & 57.9 & 7.64 & & 51.0 & 7.65 + & & 7461.53 & & 2.56 & & -3.58 & & 29.2 & 7.59 & & 37.4 & 7.53 & & & & & 48.5 & 7.67 & & 50.4 & 7.68 & & 42.0 & 7.64 + & & 7547.90 & & 5.10 & & -1.35 & & 22.6 & 7.67 & & 27.5 & 7.70 & & & & & 33.3 & 7.81 & & & & & 29.4 & 7.74 + & & 5264.81 & & 3.23 & & -3.13 & & 43.8 & 7.40 & & 42.1 & 7.82 & & 42.9 & 7.54 & & 49.9 & 8.31 & & & & & 44.0 & 7.84 + & & 5414.05 & & 3.22 & & -3.65 & & 30.7 & 7.61 & & & & & & & & & & & & & & & + & & 5425.25 & & 3.20 & & -3.39 & & 39.4 & 7.53 & & 39.7 & 7.99 & & 40.8 & 7.71 & & 41.3 & 8.32 & & 39.6 & 8.45 & & 40.5 & 7.97 + & & 6084.10 & & 3.20 & & -3.88 & & 22.0 & 7.59 & & & & & & & & & & & & & & & + & & 6247.56 & & 3.89 & & -2.44 & & 52.6 & 7.49 & & 47.4 & 7.92 & & 56.8 & 7.77 & & 52.5 & 8.37 & & 47.2 & 8.43 & & 50.5 & 7.96 + & & 6432.68 & & 2.89 & & -3.69 & & 42.0 & 7.55 & & 39.8 & 7.96 & & 41.8 & 7.70 & & 48.1 & 8.48 & & 41.5 & 8.50 & & 37.2 & 7.86 + & & 6456.39 & & 3.90 & & -2.19 & & 63.4 & 7.45 & & 55.7 & 7.86 & & 69.6 & 7.79 & & 67.1 & 8.41 & & 53.0 & 8.32 & & 63.0 & 7.98 + & & 5793.92 & & 4.22 & & -1.70 & & 40.4 & 7.54 & & 48.0 & 7.62 & & 40.5 & 7.54 & & 49.5 & 7.66 & & 48.2 & 7.69 & & 46.5 & 7.62 + & & 5856.10 & & 4.29 & & -1.64 & & 40.9 & 7.56 & & 46.7 & 7.61 & & 40.9 & 7.56 & & 49.4 & 7.66 & & 41.0 & 7.23 & & 44.3 & 7.58 + & & 5927.80 & & 4.65 & & -1.09 & & 53.0 & 7.57 & & 58.0 & 7.60 & & 51.2 & 7.54 & & 60.5 & 7.64 & & 53.2 & 7.56 & & 55.5 & 7.58 + & & 6089.57 & & 5.02 & & -0.94 & & 42.4 & 7.56 & & 49.5 & 7.64 & & 41.6 & 7.55 & & 47.0 & 7.60 & & 46.7 & 7.63 & & 54.4 & 7.73 + & & 6093.65 & & 4.61 & & -1.50 & & 38.5 & 7.67 & & 41.0 & 7.67 & & 39.0 & 7.68 & & 40.7 & 7.66 & & 40.1 & 7.69 & & & + & & 6096.67 & & 3.98 & & -1.93 & & 51.0 & 7.74 & & 54.0 & 7.72 & & 46.8 & 7.65 & & 55.2 & 7.76 & & 56.1 & 7.83 & & 51.3 & 7.70 + & & 6151.62 & & 2.18 & & -3.29 & & 63.9 & 7.55 & & 69.5 & 7.53 & & 61.7 & 7.50 & & 80.0 & 7.75 & & 70.9 & 7.68 & & 72.9 & 7.66 + & & 6165.36 & & 4.14 & & -1.47 & & 53.5 & 7.48 & & 62.3 & 7.57 & & 49.9 & 7.41 & & 56.6 & 7.48 & & 51.6 & 7.43 & & 57.0 & 7.51 + & & 6270.23 & & 2.86 & & -2.71 & & 63.5 & 7.64 & & 67.0 & 7.60 & & 64.2 & 7.66 & & 73.1 & 7.73 & & 71.2 & 7.54 & & 69.5 & 7.70 + & & 6627.56 & & 4.55 & & -1.68 & & 35.1 & 7.70 & & 41.1 & 7.78 & & 35.1 & 7.70 & & 38.6 & 7.73 & & 42.2 & 7.84 & & 39.6 & 7.76 + & & 6806.86 & & 2.73 & & -3.21 & & 46.3 & 7.60 & & 55.1 & 7.68 & & 44.6 & 7.57 & & 58.7 & 7.77 & & 49.8 & 7.66 & & 53.7 & 7.70 + & & 6839.84 & & 2.56 & & -3.45 & & 42.5 & 7.58 & & 52.0 & 7.67 & & 39.1 & 7.51 & & 46.9 & 7.57 & & 43.8 & 7.59 & & 49.6 & 7.66 + & & 6842.69 & & 4.64 & & -1.32 & & 51.0 & 7.73 & & 48.5 & 7.64 & & 48.6 & 7.69 & & & & & 49.9 & 7.70 & & 48.1 & 7.65 + & & 6857.25 & & 4.07 & & -2.15 & & 33.2 & 7.64 & & 33.0 & 7.57 & & 31.1 & 7.59 & & 35.3 & 7.63 & & 30.2 & 7.56 & & 37.6 & 7.69 + & & 6861.94 & & 2.42 & & -3.89 & & 26.6 & 7.51 & & 33.4 & 7.53 & & 26.3 & 7.50 & & & & & 32.0 & 7.61 & & & + & & 6862.50 & & 4.56 & & -1.57 & & 36.4 & 7.62 & & 42.5 & 7.70 & & 35.0 & 7.59 & & & & & 43.0 & 7.74 & & 40.3 & 7.66 + & & 7284.84 & & 4.14 & & -1.75 & & 50.8 & 7.65 & & 55.6 & 7.69 & & 48.8 & 7.61 & & & & & 48.8 & 7.60 & & & + & & 7461.53 & & 2.56 & & -3.58 & & 45.0 & 7.72 & & 48.4 & 7.68 & & 36.6 & 7.54 & & 42.2 & 7.55 & & 45.9 & 7.72 & & 47.6 & 7.71 + & & 7547.90 & & 5.10 & & -1.35 & & & & & & & & & & & 31.7 & 7.78 & & 27.0 & 7.69 & & 31.7 & 7.78 + & & 5264.81 & & 3.23 & & -3.13 & & 37.7 & 7.64 & & 36.6 & 7.91 & & 41.9 & 7.76 & & 32.7 & 7.75 & & 34.7 & 7.60 & & 37.7 & 7.79 + & & 5414.05 & & 3.22 & & -3.65 & & & & & & & & & & & & & & & & & 27.0 & 7.98 + & & 5425.25 & & 3.20 & & -3.39 & & 37.3 & 7.86 & & & & & 38.0 & 7.88 & & 32.1 & 7.96 & & 39.6 & 7.96 & & 37.3 & 8.01 + & & 6084.10 & & 3.20 & & -3.88 & & & & & & & & 21.3 & 7.88 & & & & & 14.5 & 7.66 & & & + & & 6247.56 & & 3.89 & & -2.44 & & 51.0 & 7.93 & & 38.4 & 7.96 & & 48.5 & 7.87 & & 40.7 & 7.97 & & 44.0 & 7.81 & & 43.8 & 7.93 + & & 6432.68 & & 2.89 & & -3.69 & & 36.8 & 7.82 & & 30.5 & 7.95 & & 38.6 & 7.86 & & 29.9 & 7.88 & & 35.2 & 7.82 & & & + & & 6456.39 & & 3.90 & & -2.19 & & 62.4 & 7.94 & & 51.2 & 8.03 & & 58.7 & 7.86 & & 50.6 & 7.97 & & 54.5 & 7.82 & & 57.8 & 8.02 + & & 5793.92 & & 4.22 & & -1.70 & & 47.8 & 7.65 & & 43.1 & 7.61 & & 48.0 & 7.64 & & 43.5 & 7.54 & & 26.3 & 7.58 + & & 5856.10 & & 4.29 & & -1.64 & & 46.8 & 7.63 & & 38.9 & 7.52 & & 46.6 & 7.62 & & 46.8 & 7.61 & & 24.8 & 7.55 + & & 5927.80 & & 4.65 & & -1.09 & & 57.3 & 7.61 & & 50.5 & 7.54 & & 58.3 & 7.61 & & 55.2 & 7.55 & & 34.2 & 7.52 + & & 6089.57 & & 5.02 & & -0.94 & & 51.4 & 7.69 & & 40.2 & 7.53 & & 49.5 & 7.65 & & 48.6 & 7.63 & & 30.4 & 7.60 + & & 6093.65 & & 4.61 & & -1.50 & & 47.2 & 7.80 & & 32.6 & 7.55 & & 41.2 & 7.68 & & 43.5 & 7.72 & & 24.1 & 7.66 + & & 6096.67 & & 3.98 & & -1.93 & & 49.8 & 7.67 & & 45.5 & 7.64 & & 56.1 & 7.78 & & 55.1 & 7.75 & & 29.5 & 7.65 + & & 6151.62 & & 2.18 & & -3.29 & & 72.5 & 7.66 & & 55.4 & 7.38 & & 70.5 & 7.59 & & 73.2 & 7.61 & & 36.8 & 7.51 + & & 6165.36 & & 4.14 & & -1.47 & & 57.3 & 7.51 & & 51.3 & 7.45 & & 56.5 & 7.48 & & 55.9 & 7.46 & & 37.3 & 7.50 + & & 6270.23 & & 2.86 & & -2.71 & & 71.3 & 7.74 & & 61.2 & 7.61 & & 72.9 & 7.74 & & 65.9 & 7.59 & & 44.8 & 7.70 + & & 6627.56 & & 4.55 & & -1.68 & & 34.8 & 7.66 & & 36.0 & 7.73 & & 39.6 & 7.75 & & 30.2 & 7.55 & & 21.5 & 7.70 + & & 6806.86 & & 2.73 & & -3.21 & & 56.8 & 7.76 & & 43.5 & 7.56 & & 56.3 & 7.73 & & 57.1 & 7.73 & & 23.7 & 7.62 + & & 6839.84 & & 2.56 & & -3.45 & & 51.6 & 7.71 & & 42.5 & 7.60 & & 47.9 & 7.60 & & 49.3 & 7.62 & & & + & & 6842.69 & & 4.64 & & -1.32 & & 48.5 & 7.65 & & 44.5 & 7.62 & & 49.5 & 7.67 & & 52.8 & 7.72 & & 32.5 & 7.67 + & & 6857.25 & & 4.07 & & -2.15 & & 38.2 & 7.71 & & & & & 33.3 & 7.59 & & 35.5 & 7.63 & & 17.2 & 7.60 + & & 6861.94 & & 2.42 & & -3.89 & & 41.1 & 7.76 & & & & & 36.9 & 7.64 & & 36.6 & 7.61 & & 11.0 & 7.60 + & & 6862.50 & & 4.56 & & -1.57 & & & & & & & & 44.5 & 7.74 & & 38.4 & 7.62 & & 25.3 & 7.68 + & & 7284.84 & & 4.14 & & -1.75 & & & & & & & & 57.5 & 7.73 & & & & & & + & & 7461.53 & & 2.56 & & -3.58 & & 42.4 & 7.59 & & 34.2 & 7.51 & & 44.8 & 7.62 & & 42.0 & 7.54 & & 18.9 & 7.67 + & & 7547.90 & & 5.10 & & -1.35 & & & & & 24.3 & 7.64 & & & & & 30.1 & 7.74 & & & + & & 5264.81 & & 3.23 & & -3.13 & & 34.0 & 7.69 & & 37.8 & 7.61 & & 36.9 & 7.84 & & 38.9 & 7.95 & & 51.4 & 7.48 + & & 5414.05 & & 3.22 & & -3.65 & & 23.5 & 7.86 & & & & & 21.6 & 7.86 & & & & & 30.3 & 7.53 + & & 5425.25 & & 3.20 & & -3.39 & & 33.8 & 7.91 & & 36.1 & 7.79 & & 30.8 & 7.88 & & 34.8 & 8.07 & & 48.1 & 7.63 + & & 6084.10 & & 3.20 & & -3.88 & & & & & & & & & & & 39.4 & 7.97 & & 26.5 & 7.64 + & & 6247.56 & & 3.89 & & -2.44 & & 41.0 & 7.86 & & 51.3 & 7.90 & & 38.0 & 7.86 & & 34.5 & 8.05 & & 66.6 & 7.64 + & & 6432.68 & & 2.89 & & -3.69 & & & & & 42.4 & 7.93 & & 31.5 & 7.90 & & 52.0 & 8.03 & & 48.9 & 7.61 + & & 6456.39 & & 3.90 & & -2.19 & & 51.2 & 7.87 & & 60.8 & 7.86 & & 50.8 & 7.93 & & & & & 74.1 & 7.53 + h ii 193 & & 0.06 & & 0.02 & & 0.43 & & 0.01 & & + 0.37 + h ii 250 & & 0.01 & & 0.02 & & 0.22 & & 0.05 & & + 0.21 + h ii 263 & & 0.07 & & 0.02 & & 0.89 & & 0.04 & & + 0.82 + h ii 298 & & 0.09 & & 0.01 & & 0.92 & & 0.02 & & + 0.83 + h ii 571 & & 0.02 & & 0.02 & & 0.44 & & 0.04 & & + 0.42 + h ii 746 & & 0.04 & & 0.02 & & 0.35 & & 0.06 & & + 0.31 + h ii 916 & & 0.06 & & 0.01 & & 0.49 & & 0.05 & & + 0.43 + h ii 1593 & & 0.00 & & 0.01 & & 0.35 & & 0.02 & & + 0.35 + h ii 2126 & & 0.08 & & 0.03 & & 0.42 & & 0.04 & & + 0.34 + h ii 2284 & & 0.05 & & 0.03 & & 0.28 & & 0.06 & & + 0.23 + h ii 2311 & & 0.08 & & 0.01 & & 0.45 & & 0.04 & & + 0.37 + h ii 2366 & & 0.09 & & 0.02 & & 0.34 & & 0.04 & & + 0.25 + h ii 2406 & & -0.02 & & 0.01 & & 0.33 & & 0.05 & & + 0.35 + h ii 2462 & & 0.08 & & 0.02 & & 0.37 & & 0.04 & & + 0.29 + h ii 2880 & & 0.04 & & 0.02 & & 0.53 & & 0.02 & & + 0.49 + h ii 3179 & & 0.03 & & 0.01 & & 0.06 & & 0.03 & & + 0.03 + h ii 263 @xmath90 & & @xmath91 & & @xmath92 & & @xmath93 + & & @xmath94 & & @xmath95 & & @xmath96 + & & @xmath97 & & @xmath98 & & @xmath99 + h ii 2284@xmath100 & & @xmath31 & & @xmath101 & & @xmath102 + & & @xmath103 & & @xmath104 & & @xmath105 + & & @xmath33 & & @xmath106 & & @xmath107 + h ii 3179@xmath108 & & @xmath31 & & @xmath109 & & @xmath106 + & & @xmath103 & & @xmath110 & & @xmath111 + & & @xmath33 & & @xmath98 & & @xmath112 + @xmath113 & & 0.06 & & @xcite + @xmath114 & & 0.02 & & @xcite + @xmath115 & & 0.03 & & @xcite + @xmath116 & & 0.02 & & @xcite + @xmath117 & & 0.03 & & @xcite + @xmath117 & & 0.01 & & @xcite + @xmath118 & & 0.05 & & @xcite + @xmath119 & & 0.02 & & this work + & & & & + @xmath119 & & 0.01 & & mean +	we have derived fe abundances of 16 solar - type pleiades dwarfs by means of an equivalent width analysis of and lines in high - resolution spectra obtained with the hobby - eberly telescope and high resolution spectrograph . curiously , a correlation between the pleiades abundances and chromospheric emission indicators does not exist .	we have derived fe abundances of 16 solar - type pleiades dwarfs by means of an equivalent width analysis of and lines in high - resolution spectra obtained with the hobby - eberly telescope and high resolution spectrograph . abundances derived from lines are larger than those derived from lines ( herein referred to as over - ionization ) for stars with k , and the discrepancy ( = [ /h ] - [ /h ] ) increases dramatically with decreasing , reaching over 0.8 dex for the coolest stars of our sample . the pleiades joins the open clusters m34 , the hyades , ic2602 , and ic2391 , and the ursa major moving group , demonstrating ostensible over - ionization trends . the pleiades abundances are correlated with infrared triplet and h chromospheric emission indicators and relative differences therein . oxygen abundances of our pleiades sample derived from the high - excitation triplet have been previously shown to increase with decreasing , and a comparison with the abundances suggests that the over - excitation ( larger abundances derived from high excitation lines relative to low excitation lines ) and over - ionization effects that have been observed in cool open cluster and disk field main sequence ( ms ) dwarfs share a common origin . curiously , a correlation between the pleiades abundances and chromospheric emission indicators does not exist . star - to - star abundances have low internal scatter ( dex ) , but the abundances of stars with k are systematically higher compared to the warmer stars . the cool star [ /h ] abundances can not be connected directly to over - excitation effects , but similarities with the and triplet trends suggest the abundances are dubious . using the [ /h ] abundances of five stars with k , we derive a mean pleiades cluster metallicity of [ fe / h ] .
astro-ph0502575	c	it is conventional to believe ( e.g. leahy 1993 ) that the jets of wat sources are physically similar to those in classical double ( frii ) radio galaxies and quasars ; evidence for this comes from their narrow and sometimes one - sided appearance ( as in 3c465 ) , the polarization structure they exhibit and their frequent termination in compact , shock - like features similar to the hotspots in friis ( hardcastle & sakelliou 2004 ) . x - ray emission from frii - like ( ` type ii ' ) jets , particularly in quasars and other sources where the jet is _ a priori _ thought to make a small angle to the line of sight , is often attributed in the literature to inverse - compton scattering of the cosmic microwave background radiation by a jet with a high bulk lorentz factor ( @xmath72 ) , based on the observations that a one - zone synchrotron model can not be fitted to the data and that the inverse - compton process without beaming requires a large departure from the equipartition condition ( e.g. tavecchio et al . 2000 ) . however , the generally accepted picture of x - ray emission from fri - like ( ` type i ' ) jets is that they are due to synchrotron emission related to the strong deceleration of the jet flow expected on other grounds in the inner few kpc of these systems ( e.g. hardcastle et al.2001 , 2002 ) ; in these cases a one - zone synchrotron model is often a good fit to the overall jet spectrum ( although the details of jet structure may in fact be complex on scales that can not be resolved in most sources : hardcastle et al . 2003 ) while a beamed inverse - compton model requires implausible jet parameters . the detection of 3c465 s inner jet in x - rays , at a level similar to what would be predicted using a simple synchrotron model based on observations of type i jets , lends support to the idea that some type ii jets can be synchrotron sources . there is already evidence for this from the comparatively strong detections of the pre - flaring jets , thought to be type ii , in some fri sources , notably 3c66b and cen a ( hardcastle et al . 2001 , 2003 ) as well as x - ray detections of components of the jets of some frii sources ( e.g. 3c219 , comastri et al . 2003 ; 3c452 and 3c321 , hardcastle et al . 2004 ; 3c403 , kraft et al . 2005 ) for which it is highly implausible that a beamed inverse - compton model can be an explanation . 3c465 is particularly interesting in this context for three reasons : ( 1 ) it is generally accepted that wat jets are type ii , ( 2 ) the emission from the jet is not confused by inverse - compton emission from any surrounding lobes , and ( 3 ) there is no confusion between jet knots and hotspots , which can also be synchrotron x - ray sources . 3c465 s detection thus gives us a reason to reiterate a point already made by hardcastle et al . ( 2004 ) and kraft et al . ( 2005 ) : there are clearly x - ray - emitting type ii jets for which the beamed inverse - compton model is _ not _ the explanation . since there is no compelling reason to expect a one - zone synchrotron model to be a good fit in an frii jet in which the loss spatial scale may be two to three orders of magnitude smaller than the region of the jet being considered , observers should be wary of ruling out the possibility that synchrotron emission is responsible for the x - rays from a given type ii jet . on the other hand , the non - detection of the bases of the plumes of 3c465 in x - rays , at a level sufficient to show that their radio to x - ray spectral index is significantly greater than that seen in all fri jets , strongly suggests that these regions are _ not _ analogous to the bases of type i jets . this is as expected in the picture of these objects proposed by hardcastle et al . ( 1998 ) and hardcastle & sakelliou ( 2004 ) , in which the jet decelerates rapidly at a single point close to the base of the plume , rather than there being uniform distributed deceleration over a finite - sized region of the base of the plume . we conclude that the non - detection of the plumes in x - rays in the _ chandra _ observations is evidence that the bases of wat plumes are physically different from the bases of fri type i jets ; wat plumes are probably more similar to the large - scale jets of fris , which typically do not show either strong deceleration or x - ray emission . it is not clear why we do not see x - ray emission associated with the assumed rapid deceleration of the jet at the base of the plume , by analogy with the x - ray emission detected from the hotspots of many low - luminosity frii radio galaxies , thought to be synchrotron in origin ( hardcastle et al . 2004 and references therein ) . features as faint as the brightest knot at the end of the n jet ( nj2 in the notation of hardcastle & sakelliou : see also fig . [ pbase ] ) have been detected in x - ray observations of frii hotspots . however , as we noted above , there is no particularly good candidate feature analogous to a hotspot in the radio images of 3c465 ; the jet flow clearly continues after nj2 . _ chandra _ images of wats that _ do _ exhibit compact bright jet termination structures would be of considerable interest . we begin by noting that the conclusions of jetha et al . ( 2005 ) , based on less sensitive observations , apply to 3c465 as well . there is no evidence in the data either for discrete features associated with the jet termination points or plume bases or for discontinuities in the properties of the external medium at the distances of the jet - plume transition , such as the shock structures in the models of loken et al.(1995 ) ; in particular , our observations show that the apparent temperature discontinuity seen in the inner regions of the sources studied by jetha et al . was probably an unresolved temperature gradient . models that require a discontinuity in the external medium are thus ruled out by observation . the jet termination is on a similar scale to the transition between the central , cool x - ray core and the hotter cluster medium , again as observed by jetha et al . , but as yet we have no clear idea of why this should be the case . as jetha et al.suggest , numerical modelling of realistic ( fast , low - density ) jets and plumes in realistic cluster environments may be the way forward here . it is also interesting to note that the transition occurs close to the point where the jet internal ( minimum ) pressure starts to exceed the external thermal pressure ( section [ cluster ] and fig.[pprofile ] ) . x - ray and radio data of similar quality for a larger number of sources would be required to say whether this is more than a coincidence . our detailed x - ray and radio observations have given a very clear indication that the large - scale plumes of 3c465 behave similarly to the lobes or plumes of normal twin - jet fri sources : the minimum pressures in the lobes are about an order of magnitude below the external thermal pressures . this implies some sort of departure from the minimum - energy condition , either a departure from equipartition between the radiating electrons and magnetic fields , a population of non - radiating relativistic particles , or a contribution to pressure from particles that do not participate in equipartition , such as thermal protons . as usual ( e.g. hardcastle et al . 1998 , croston et al.2003 ) we can not tell which of these is the case . in the inner parts of normal fri jets the jet deceleration is thought to be by entrainment of external material , which has suggested that the entrained material might supply the missing pressure if it could be heated efficiently so as to avoid thermal x - rays from the lobes or plumes ( see e.g. croston et al . 2003 ) . in wat plumes , the jets are not expected to have entrained significant amounts of external material , since they do not show the deceleration - related structures of fri jets , and so this explanation seems less likely ( see also below , section [ bending ] ) . on the other hand , if we assume that equipartition does not hold , it is not clear why such a large departure from equipartition should be required in wat plumes but not in frii lobes , where inverse - compton evidence ( e.g. hardcastle et al . 2002 , belsole et al . 2004 , croston et al . 2004 ) suggests that equipartition is roughly maintained and that the electrons and magnetic fields alone are sufficient to provide pressure balance with the external medium . the departure from equipartition would correspond to around a factor 5 difference between the actual magnetic field strength and the equipartition value ; this is considerably larger than is typically seen in the x - ray - detected lobes of frii radio galaxies ( croston et al . in addition , a departure from equipartition sufficient to make the internal pressure equal to the external pressure in the direction of electron domination would give rise to strong inverse - compton emission from the plumes , at the level of a few thousand _ xmm _ counts , which is not observed the deficits in x - ray count rate seen at the bases of the plumes seem to rule out this model , so that the lobes would have to be magnetically dominated if electrons and magnetic field alone were to supply the required pressure . the third possibility is that the plumes contain an energetically dominant population of relativistic protons : this can not be ruled out directly by the data , but again arguments based on inverse - compton detections suggest that it is not the case in the hotspots ( hardcastle et al . 2004 ) or lobes ( croston et al . 2005 ) of frii sources . we return to the particle content of the plumes in the next section . it is instructive to revisit the arguments of e84 that led to the conclusion that the bending of 3c465 in particular , and of wats in general , was difficult to explain in any model . they assumed that the kinetic energy of the plume must supply the overall observed radio luminosity : that is , the bulk flow is cold and there is _ in situ _ particle acceleration at all points in the plume . this leads to a condition on the density and speed of a non - relativistic plume : @xmath73 ( their eq . 2 ) where @xmath74 is a factor giving the efficiency of conversion between kinetic energy and energy of relativistic electrons , @xmath75 is the plume radius , @xmath76 is its density and @xmath77 is its speed . they assumed _ in situ _ particle acceleration on the basis of estimates of the synchrotron loss timescale at 5 ghz , and so we note to begin with that it may not be necessary to satisfy this condition in its original form . the synchrotron age of material at the end of the plumes is @xmath78 years , based on 1.4 ghz and 330 mhz data taken from the vla archives , if we assume a jaffe & perola ( 1973 ) aged synchrotron spectrum , an injection index of 2.0 and a loss magnetic field strength around the minimum - energy value of 0.4 nt ( taking into account cmb losses ) , and consequently material can be transported out from the jets or plume bases without _ in situ _ reacceleration so long as @xmath79 , or 2500 km s@xmath2 . e84 used the lack of observed depolarization to place a limit ( @xmath80 m@xmath49 ) on the density of thermal material ( effectively , protons ) in the tails . this method of setting a density limit has fallen out of favour in recent years , partly because it does not provide a strong upper limit ( laing 1984 ) and partly because it seems unlikely that the limits it does provide are close to the true values , which may be much lower . it may thus not be appropriate to use a proton density around @xmath81@xmath82 m@xmath49 as a ` typical ' value in the plumes . observationally , there are few other constraints on the internal density available : as discussed above , we know from the x - ray deficits seen in both ordinary fris and in cluster - centre objects ( e.g. brzan et al . 2004 ) that the missing pressure in these sources is _ not _ supplied by thermal protons at the temperature of the external medium , but this only really gives the constraint that the internal density is likely to be much lower than the external one . a true limit comes from considering the minimum possible internal density . if we assume that the wat plumes are in pressure balance and that the internal pressure is supplied by relativistic particles and magnetic field , presumably with some departure from the minimum energy condition , the plume material remains very light compared to the external medium : we require @xmath83 , where @xmath84 , and the effective density of the internal material is @xmath85 , while the external density is @xmath86 , where @xmath87 is the mass per particle in atomic mass units ( about 0.6 ) . the density contrast is thus @xmath88 , or about @xmath89 for the temperature of the 3c465 cluster . the internal density ( in terms of an equivalent proton density ) in this model , which represents a minimum possible internal density if we think that the plumes are not underpressured , would be of the order of 0.04 m@xmath49 , much lower than the ` typical ' values used by e84 . such a light plume is comparatively easy perhaps even too easy to bend by ram pressure ; if the flow speed up the plume , @xmath77 , were comparable to the local external sound speed ( @xmath90 km s@xmath2 ) , bulk motions with speeds of @xmath91 would have a significant effect , while if @xmath77 were comparable to the speed estimated above from spectral ageing arguments , we would require external bulk motions with speeds around @xmath92 . if instead we adopt the luminosity condition ( eq . [ lum ] ) to estimate the flow speed , retaining this low internal density , then we would obtain a bulk speed around @xmath93 [ for a radiative efficiency of 0.1 , which may be generous , in view of the jet luminosity inferred for the weaker source 3c31 by laing & bridle ( 2002 ) ] and , because of the low internal density , bulk motions with speeds around @xmath94 would still be sufficient to bend the plume : as e84 comment , low jet densities are possible , but require high speeds if the luminosity condition is to be satisfied . if , on the other hand , the pressure deficit at minimum energy is supplied by hot , entrained , internal thermal material , as is possible for fri lobes , then we know only that the density contrast is @xmath95 ( since the thermal protons then dominate the density of the flow ) and in that case external bulk motions at the sound speed can bend the plume significantly if @xmath96 , which for moderate heating of the internal protons requires plume speeds that are at most mildly supersonic : for example , if the plume speed is 2500 km s@xmath2 , then the internal protons must be heated to around 20 kev ( which would also give a density for internal protons that was close to the ` limit ' on internal density inferred by e84 ) . bending by subsonic motions requires a correspondingly higher temperature , increasing as @xmath97 , but this is not impossible , as we have little information on the temperature of the internal protons . in the case of a proton - dominated plume the luminosity condition , eq . [ lum ] , requires @xmath98 , and it can be shown that very high internal temperatures ( @xmath99 k ) , correspondingly low densities , and high plume flow speeds ( @xmath100 ) are required for the plume to be bent by sub - sonic bulk motions in the external medium . to summarize , the plumes can be bent by bulk motions in the external medium if they are light , but they will only also meet the luminosity condition of e84 if they are also fast . if we drop the assumption of _ in situ _ acceleration ( and instead assume passive transport of radiating electrons ) then the plumes need only be mildly supersonic , but must still be light . this conclusion revives the possibility that the plumes are in fact bent by the motion of the galaxy with respect to the host cluster . e84 suggest that the systematic motion of ngc 7720 could be of order 100300 km s@xmath2 , or @xmath101@xmath102 . their estimate does not necessarily rule out higher galaxy speeds , because they base it on the radial velocity of the galaxy with respect to the cluster mean ( which does not tell us about motions in the plane of the sky ) and on studies of the radial velocities of cds in general ( which may not be representative of the systems hosting wats ) . the possible detection of an x - ray wake behind 3c465 ( section [ wake ] ) may indicate a higher speed . nevertheless , it is interesting that the speed estimate of e84 is within the range estimated above for plume bending either if the plume s internal pressure is supplied entirely by relativistic particles and the plume is fast , or if a slower plume s internal pressure is supplied by very hot thermal material . is this picture consistent with the fact that the inner jets are not bent ? this question is more difficult to answer because we do not have a reliable estimate for the inner jet speed or density , and we can not assume pressure balance in the jet . if we assume @xmath103 ( from the beaming analysis ) and take the minimum equivalent internal density to be given by @xmath104 , using the minimum pressure plotted in fig . [ pprofile ] , then we can use euler s equation in the form @xmath105 where @xmath106 is the radius of curvature of the jet , @xmath107 is the galaxy speed , and @xmath108 is the width of the jet . ( the non - relativistic approximation is not badly wrong in this case . ) from the radio maps we can see that the radio jet bends , if it bends at all , by less than one jet width over its observed length @xmath109 . taking @xmath110 arcsec ( which includes the effects of projection with @xmath111 ) , @xmath112 arcsec , and an external density comparable to that at the transition between the hot and cool components in the x - ray ( 1500 protons m@xmath49 ) we find that speeds of 120 km s@xmath2 could produce a bend of one jet width . as this is very consistent with the possible values for systematic motion of the galaxy , and as our estimate of @xmath113 is a lower limit , we are satisfied that an explanation for the plume bending in terms of the systematic motion of the galaxy through the cluster is not inconsistent with the observations of essentially straight inner jets , provided that the jets are fast . we emphasise , however , that this model is only viable if the plume is light . if there is substantial entrained thermal material , then the analysis above suggests that sub - sonic motion of the galaxy through the cluster material is too slow to have a significant effect on the plumes . it is interesting in this context that there is a population of wat sources with bent inner jets ( exemplified by 0647 + 693 , hardcastle & sakelliou 2004 ) : if the jets in these sources _ are _ bent by ram pressure due to the host galaxy s motion , then the model we have discussed suggests either that the jets in these sources are weaker ( transport less energy ) or slower , or that the systematic motions of the host galaxies are larger . we will investigate this possibility in more detail elsewhere . [ fri - wat ] these results , combined with those of the previous subsection , mean that there are some interesting possible differences between wats and classical fri sources . on the one hand , we have shown ( section [ pcontent ] ) that the large - scale plumes of 3c465 are very similar to the extended structure of other fri sources in terms of the difference between the minimum internal pressure and the external pressure : in fris one of the best explanations for this observation is that the pressure deficit is supplied by heated , entrained material . on the other hand , as we have seen , bending of the 3c465 plumes by galactic motions puts limits on the amount of entrained material that is present : for example , if we adopt a plume speed of 2500 km s@xmath2 , then significant bending by bulk speeds of @xmath114 km s@xmath2 require thermal densities several orders of magnitude below the external density ( with correspondingly high temperatures if we want this material to supply the missing pressure ) , while satisfying the e84 luminosity condition requires even lower densities . these densities are considerably lower than the densities estimated by odea ( 1985 ) from the bending of narrow - angle tail ( nat ) sources . although it would be interesting to revisit the calculations of odea with modern estimates of the external density , and to compare them to estimates of the proton density required to provide pressure in the lobes , this may be an indication that type ii jets such as those in 3c465 are less efficient at entraining thermal material than the type i jets of nats .	chandra _ and _ xmm - newton_. x - ray emission is detected from the active nucleus and the inner radio jet , as well as a small - scale , cool component of thermal emission , a number of the individual galaxies of the host cluster ( abell 2634 ) , and the hotter thermal emission from the cluster itself . the x - ray detection of the jet allows us to argue that synchrotron emission may be an important mechanism in other well - collimated , fast jets , including those of classical double radio sources . the bases of the radio plumes are not detected in the x - ray , which supports the model in which these plumes are physically different from the twin jets of lower - power radio galaxies . the plumes are in fact spatially coincident with deficits of x - ray emission on large scales , which argues that they contain little thermal material at the cluster temperature , although the minimum pressures throughout the source are lower than the external pressures estimated from the observed thermal emission . our observations confirm both spatially and spectrally that a component of dense , cool gas with a short cooling time is associated with the central galaxy . however , there is no evidence for the kind of discontinuity in external properties that would be required in many models of the jet - plume transition in wats . galaxies : active x - rays : galaxies galaxies : individual : 3c465 galaxies : jets radiation mechanisms : non - thermal	we have observed the prototypical wide - angle tail radio galaxy 3c465 with _ chandra _ and _ xmm - newton_. x - ray emission is detected from the active nucleus and the inner radio jet , as well as a small - scale , cool component of thermal emission , a number of the individual galaxies of the host cluster ( abell 2634 ) , and the hotter thermal emission from the cluster itself . the x - ray detection of the jet allows us to argue that synchrotron emission may be an important mechanism in other well - collimated , fast jets , including those of classical double radio sources . the bases of the radio plumes are not detected in the x - ray , which supports the model in which these plumes are physically different from the twin jets of lower - power radio galaxies . the plumes are in fact spatially coincident with deficits of x - ray emission on large scales , which argues that they contain little thermal material at the cluster temperature , although the minimum pressures throughout the source are lower than the external pressures estimated from the observed thermal emission . our observations confirm both spatially and spectrally that a component of dense , cool gas with a short cooling time is associated with the central galaxy . however , there is no evidence for the kind of discontinuity in external properties that would be required in many models of the jet - plume transition in wats . although the wat jet - plume transition appears likely to be related to the interface between this central cool component and the hotter intra - cluster medium , the mechanism for wat formation remains unclear . we revisit the question of the bending of wat plumes , and show that the plumes can be bent by plausible bulk motions of the intra - cluster medium , or by motion of the host galaxy with respect to the cluster , as long as the plumes are light . galaxies : active x - rays : galaxies galaxies : individual : 3c465 galaxies : jets radiation mechanisms : non - thermal
astro-ph0502575	c	our principal results can be summarized as follows : 1 . the detection of x - ray emission from the inner part of the jet of 3c465 adds significantly to the evidence that fast ( at least mildly relativistic ) , efficient , frii - like ( ` type 2 ' ) jets can be sources of x - ray synchrotron radiation . 2 . the non - detection of x - ray emission from the jet termination point and the bases of the plumes rules out a model in which the plume bases resemble the bright bases of fri radio jets , which are often x - ray synchrotron sources : this is consistent with our favoured model for the wat jet - plume transition , in which the deceleration of the fast inner jets takes place rapidly when the jet interacts with the external medium at the edge of the plume , rather than slowly by entrainment as in fri jets . however , it is interesting that there is no detection of synchrotron x - rays from any of the plausible candidates for the jet termination ` hotspot ' in 3c465 , unlike the situation in the ( supposedly physically similar ) hotspots in low - power frii sources . more x - ray observations of wats with bright jet termination hotspots are required . we have made detailed measurements of the temperature and density structure of 3c465 s host cluster , a2634 , and in particular have resolved a central dense , cool thermal component with a relatively short cooling time , which is similar to the components seen in other wats and to the central components of fri sources in groups . there is no evidence for any discontinuity in the properties of the external medium , and so we conclude , following jetha et al . ( 2005 ) , that models of wat formation that require such discontinuities are ruled out . the most likely scenario based on our observations and those of jetha et al . is that the location of the jet - plume transition is related to the emergence of the jet from the small - scale cool component associated with the host galaxy , but the physical mechanism that sets the location of the plume base remains unclear . our observations show that the minimum pressures of the plumes fall below the pressures estimated for the external thermal material : this implies either some departure from the minimum - energy ( equipartition ) condition or an additional contribution to pressure from low - density , hot thermal material . the plumes of wats are thus similar to the large - scale components of more normal fri sources . 5 . revisiting the arguments related to wat plume bending , we find that the plumes can be bent by sub - sonic bulk motions of the icm , or by plausible motion of the host galaxy through the icm , provided that they are extremely light with respect to the external medium ( as would be the case if their internal pressures were dominated by relativistic particles and/or magnetic field ) .	although the wat jet - plume transition appears likely to be related to the interface between this central cool component and the hotter intra - cluster medium , the mechanism for wat formation remains unclear . we revisit the question of the bending of wat plumes , and show that the plumes can be bent by plausible bulk motions of the intra - cluster medium , or by motion of the host galaxy with respect to the cluster , as long as the plumes are light .	we have observed the prototypical wide - angle tail radio galaxy 3c465 with _ chandra _ and _ xmm - newton_. x - ray emission is detected from the active nucleus and the inner radio jet , as well as a small - scale , cool component of thermal emission , a number of the individual galaxies of the host cluster ( abell 2634 ) , and the hotter thermal emission from the cluster itself . the x - ray detection of the jet allows us to argue that synchrotron emission may be an important mechanism in other well - collimated , fast jets , including those of classical double radio sources . the bases of the radio plumes are not detected in the x - ray , which supports the model in which these plumes are physically different from the twin jets of lower - power radio galaxies . the plumes are in fact spatially coincident with deficits of x - ray emission on large scales , which argues that they contain little thermal material at the cluster temperature , although the minimum pressures throughout the source are lower than the external pressures estimated from the observed thermal emission . our observations confirm both spatially and spectrally that a component of dense , cool gas with a short cooling time is associated with the central galaxy . however , there is no evidence for the kind of discontinuity in external properties that would be required in many models of the jet - plume transition in wats . although the wat jet - plume transition appears likely to be related to the interface between this central cool component and the hotter intra - cluster medium , the mechanism for wat formation remains unclear . we revisit the question of the bending of wat plumes , and show that the plumes can be bent by plausible bulk motions of the intra - cluster medium , or by motion of the host galaxy with respect to the cluster , as long as the plumes are light . galaxies : active x - rays : galaxies galaxies : individual : 3c465 galaxies : jets radiation mechanisms : non - thermal
astro-ph0412501	i	cataclysmic variables ( cvs ) are interacting binary systems in which a white dwarf ( wd ) accretes matter from a low - mass companion . in non - magnetic cvs , the in - falling matter forms a disk around the wd . dwarf novae ( dne ) are disk - accreting cvs that undergo sharp rises in luminosity , during which the optical brightness typically increases by 2 to 5mag . the outbursts occur when a sudden increase in the gas viscosity ( due to a change in the ionization state of the gas ) allows matter to flow more rapidly through the disk , causing an increase in the accretion luminosity . in most dne , outbursts last for a day to a few weeks . in the subclass of dne known as u gem systems , outbursts end with a steady decline to minimum that has a typical timescale of a day however , in z cam systems , the decline from outburst occasionally stalls about 1mag below the peak . such ` standstills ' can last for days to , in a few cases , years . other non - magnetic cvs ( nova - like variables ) appear to remain persistently in the outburst state . the z cam standstill state is comparable to that of a nova - like variable , i.e. a steady , high state , but somewhat lower in luminosity than the peak of a dwarf nova outburst . the difference in outburst behavior between u gem , z cam and nova - like systems is thought to reflect a difference in the rate of mass flow from the secondary ( ) . in dne , is below the upper stability boundary ( ) for which dn outbursts can occur , whereas in nova - like systems @xmath1 . in z cam - type stars @xmath2 lies very near , but below @xmath3 most of the time . standstill phases are triggered when an increase in @xmath2 @xcite is accompanied by a decrease in @xmath3 as a response to heating of the outer edge of the accretion disk by the increased mass transfer @xcite . thus , @xmath2 becomes greater than @xmath3 and the disk assumes a stable high state ( like a nova - like variable ) . it has been difficult to measure mass transfer rates in cvs observationally , and as a result reliable empirical determinations of and are lacking . on theoretical grounds , is thought to be about when heating of the mass transfer stream is taken into account @xcite . z cam is the brightest ( in outburst ) and most extensively studied object of its class . it has an orbital period @xmath4d , which implies that it , like other standstill systems , is above the period gap . ( a complete list of system parameters is presented in table [ t : param ] . ) the difference in the magnitude at outburst maximum ( @xmath5=10.4 ) and quiescence ( @xmath613 ) is small for dne in general , but typical of standstill systems . the standstill @xmath5 averages 11.5 @xcite . far ultraviolet ( fuv ) spectra of z cam in outburst were obtained with the hopkins ultraviolet telescope ( hut ) @xcite . the outburst spectrum resembles that of a steady - state accretion disk with a mass accretion rate = , modified by resonant scattering by material in a wind @xcite . here , we attempt to complete the picture of z cam by describing fuv spectra of z cam in the quiescent and standstill states . we utilize spectra of z cam in quiescence that we have obtained using _ far ultraviolet spectroscopic explorer _ ( ) , and a spectrum of z cam in standstill obtained with telescope that we retrieved from the mast archive . our discussion of the effort to understand the two datasets is organized as follows : in section [ s : obs ] , we describe the data reduction and the mean spectrum of z cam in quiescence . in section [ s : cont ] , we attempt to fit the spectrum of z cam in quiescence , while in section [ s : var ] we analyze the time variability of the spectral lines . in section [ s : stand ] , we describe the spectrum of z cam in standstill as well as our attempts to model that spectrum . finally , in section [ s : discus ] , we evaluate the available spectral models and compare the properties of z cam in its different luminosity states .	a second component could be due to a rotating accretion belt , a remnant of an outburst that ended eleven days prior to the observation , or ongoing accretion . we have compared the quiescent spectrum with an archival spectrum of z cam in standstill , obtained with .	we have obtained _ far ultraviolet spectroscopic explorer _ ( 9051187 ) spectra of the non - magnetic cataclysmic variable z cam during a period of quiescence . the spectrum resembles that of a hot ( 57,000k ) metal - enriched white dwarf . a high effective temperature is consistent with the expectation that dwarf nova systems that show standstills , as z cam does , have higher than normal time - averaged mass accretion rates . it is also consistent with current estimates for the mass and distance to z cam . a white dwarf model in which 29% of the surface has a temperature of 72,000 k and the rest of the surface is at 26,000k also reproduces the spectral shape and the continuum flux level at the nominal distance and wd mass , and is a somewhat better statistical fit to the data . a second component could be due to a rotating accretion belt , a remnant of an outburst that ended eleven days prior to the observation , or ongoing accretion . we favor the uniform temperature model for z cam , largely because the data do not require anything more complicated . we have compared the quiescent spectrum with an archival spectrum of z cam in standstill , obtained with . the standstill spectrum is described well by a disk accreting at = , where the errors depend on the assumed inclination . the quiescent spectra cover a full orbital period and are time - resolved tos . no variability was observed in the continuum during the observation , but the depth of many of the absorption lines increased between orbital phases 0.65 and 0.81 . we attribute this effect to absorption by material associated with the accretion stream , which is easier to understand if the inclination is near the maximum allowed value of 68 .
astro-ph0412501	c	in quiescence , we find that the fuv continuum of z cam as observed by is qualitatively well - described in terms of emission from a hot metal - enriched wd atmosphere . for log g=8.5 , the best fit single temperature models has a of 57,200 k and of . the mass of the wd in z cam is estimated to be 0.99@xmath620.15 , which suggests of . thus the two measurements of can be reconciled if the distance to z cam is @xmath63 pc , where the errors here are calculated from the uncertainty in the mass . this is slightly larger than , but wholly consistent with the astrometric distance of @xmath64 pc . if this interpretation is correct , then the wd in z cam is hot when compared to the wds in other cvs . a recent compilation of reliably determined wd temperatures in cvs by @xcite contains 34 objects ( other than z cam ) ranging in temperature from 9,500 k in the polar ef eri to 50,000 k in the nova - like variable and sw sex star dw uma . a temperature of 57,200 k would make z cam the hottest wd in a cv , excepting only v1500 cyg , which is still cooling from its nova outburst in 1975 and for which there is a crude blackbody temperature estimate of 70,000 to 120,000 k for the wd @xcite . is this reasonable ? the surface temperatures of wds in cvs are thought to be primarily determined by the accretion history of the wd @xcite . this is because although the wds in cvs emerge from the common envelope phase as very hot wds , the wds cool to temperatures of 4,500 - 6000 k in the 3 - 4 gyr required to reach the mass - exchanging stage . accretion reheats the surface layers of the wd on the time scales of outbursts ( weeks ) , as is evidenced from observations of temperature changes in wds in cvs such as u gem @xcite and vw hyi @xcite . more importantly , accretion reheats the entire wd over longer time scales ( ) , as the envelope and core adjust to the increase in mass of the wd , an effect known as compressional heating , and through nuclear burning of the accreted material @xcite . recently , @xcite have determined the relationship between time - averaged accretion rate and wd temperature . for a temperature of 57,000 k , the required rate is @xmath7 ( with uncertainties of perhaps a factor of two ) . ( a somewhat lower value of is obtained for 45,000 k , the temperature derived from the combined + spectrum . ) thus the accretion rate required is high , although it may be consistent with the fact that z cam is commonly in ( or near ) the high state . indeed , of the four systems with wd temperatures greater than 40,000 k , mv lyr , tt ari , ru peg , and dw uma , all but ru peg are nova - like variables and hence , like z cam , are systems where there are other indications of high time - averaged accretion rates . given this , we believe a temperature of 57,000 k is reasonable . an alternative interpretation of the quiescent spectrum is that the surface temperature of the wd in z cam is not uniform . our analysis shows that a somewhat better , but still not statistically acceptable fit to the data can be obtained if 2 t models are considered . our best fit had a low temperature component with @xmath36 of 26,300 k covering 71% of the surface and a high temperature component with @xmath37 of 71,700 k covering 29% . if the low temperature component represents energy loss from the interior of the wd while the high temperature component is due to recent or ongoing accretion , then 94% of the luminosity of the wd is due to recent accretion . is this reasonable ? if the excess emission is due to ongoing accretion , then the observed luminosity is @xmath65 , where @xmath66 is the fraction of gravitational energy available that is radiated . for the best 2 t parameters , the excess luminosity is , and the implied value of @xmath67 is . this is a fairly large value for a disk in quiescence , especially since @xmath68 , but is hard to rule out because of our lack of good models for emission from quiescent disks and the brightness of the wd itself . on the other hand , the accretion belt hypothesis is that some of the kinetic energy of material that reaches the boundary layer between the disk and wd is stored in a rapidly rotating belt and released slowly during the interoutburst period . in standard accretion disk theory , half of the gravitational energy of material accreted by the wd is radiated by the disk and half remains as kinetic energy when it enters the boundary layer . for z cam , with a disk accretion rate of , the disk luminosity is . for the outburst that preceded the observation , z cam remained within 1 mag . of outburst maximum for about 4 days ( see fig.[f : aavso ] ) , and hence the total energy release was about . the observation occurred about 11 days from the return to quiescence and , as noted previously , the belt luminosity in the context of this hypothesis was still . we do not have the coverage to determine the time decay of the second component , but a conservative lower limit is obtained by assuming constant luminosity until the observation and zero from then on . by this argument the energy stored in the rotating layer was at least , or 8% of the energy of the outburst . if one assumes an exponential decay , then the energy release is @xmath69 , where t is the time from outburst , l(t ) the luminosity at the time of our observation , and @xmath70 the decay time constant . if @xmath70 was 11 days , then the total energy released would be @xmath71 greater , or 20% of the total outburst energy . in either case , the energy that must be stored in the belt is large , though not energetically disallowed . if the hot component is produced by short - term effects of accretion , then the low t component reflects the long - term average of accretion . for a temperature of 26,300 , this requires an accretion rate of . this is lower than the number inferred from 1 t fits , but still substantial . so how does one decide between the two models we have explored for z cam in quiescence ? the data are not definitive . the model parameters that result from both models are substantially in agreement with other known parameters of the system . is somewhat better for the 2 t model than the uniform temperature model . but is much greater than 1 per degree of freedom in the 2 t model , showing that it is at best a step toward a correct model of z cam in quiescence , and the systematic errors in the spectrum are difficult to quantify . the differences in the two model spectra are quite small ; there is no characteristic of the spectrum that one can point to that requires a second component . evidence that for the high temperature component is high compared to the low t component is lacking . in u gem @xcite , single temperature models lead to a physically implausible result , namely that the wd grows in radius during quiescence . since we do not have multiple observations of z cam through a quiescent period , we do not know whether single t models lead to a similar problem in z cam . there are other well - observed systems , e.g. vw hyi @xcite and wz sge @xcite , which do not exhibit `` radius growth '' in the context of one temperature models , and so one can not use that as a guide . there is also no consensus theoretically . while @xcite have argued that mass transfer from the disk is higher immediately after outburst in order to explain uv delays in dne , the expected x - ray evidence of a gradual decline in hard x - ray emission following outbursts is lacking . furthermore the x - ray data that exist indicates that the x - ray plasma that exists in quiescence is not rotating rapidly @xcite , and therefore it is hard to understand how it could produce a heated annular region around the surface . while @xcite postulated the existence of accretion belts and described an instability that might release energy in an accretion belt , there are to our knowledge no detailed calculations of expected properties of the emitting region and no attempt to calculate the luminosity of the rotating component with time . given these considerations , our answer to the question of which model is most likely correct is to appeal to occam s razor and assert that the simpler 1 t model provide a good physical description of the data and is therefore is the best - bet physical model to pursue . in outburst , @xcite showed that the shape of the fuv ( 9001800 ) continuum of z cam could be modeled as an accretion disk with @xmath72 at an inclination of 57 and distance of 170 pc ( very close to the best astrometric distance of 163 pc ) . in the high state , the fits are self - consistent . in standstill we find @xmath73 . approximately , then , there appears to be at least an order of magnitude increase in from quiescence to standstill , while is an order of magnitude higher still . our derived gives an upper limit on , as it is a reasonable assumption that is also the rate of mass flow from the secondary at that time , which must be greater than . @xcite calculate @xmath74 , using the formula of @xcite and taking into account heating by the stream disk impact ( or if tidal dissipation is also included ) . our upper limit of @xmath75 is just consistent with this and with the upper limit of @xmath76 derived by @xcite . the comparison of the befs standstill spectrum and the spectrum of z cam in quiescence illustrates the problem of separating a wd spectrum from that of a disk . except for the flux level the qualitative differences between the befs spectrum and the spectrum are relatively small . in both states , the continuum slope is almost the same and , other than a slight increase in ionization temperature , their line spectra are very similar . yet , we find that in quiescence a wd alone can make up the continuum flux , whereas in standstill an accretion disk is the best model for the continuum flux . ultimately , the key model parameter that has enabled us to fit one model and reject others is the normalization required to match the observed and the modeled flux levels , which in turn depends on the wd mass and the distance from the sun . without a reasonably accurate knowledge of these parameters it would be impossible to judge between a wide range of models that reproduce the continuum slope and line spectrum equally well . in the time - resolved spectra of z cam in quiescence , we have seen enhanced line absorption between phase 0.65 and 0.81 , which covers the full range of atomic species and excitation levels . the enhanced absorption is very well centered on the mean line profile , which , in turn , is centered 100200 to the red of the transition rest velocity . the change in absorption width is greatest in those lines that are weak or absent from the mean spectrum , but also encompasses lines which are thought to be optically thick in the mean spectrum , leaving only the n@xmath13924 , o@xmath13@xmath321032,1038 and c@xmath13977 and 1176 lines unchanged . flux variations at around phase 0.50.8 are seen in a selection of disk - accreting systems , in phenomena such as dips in the uv @xcite and x - ray @xcite light curve of low - mass x - ray binaries and cv , and humps in the optical light curves of cv ( e.g. * ? ? ? this is typically attributed the interaction of the accretion stream from the secondary with the outer edge of the accretion disk . this can result in a luminous ` bright spot ' at the outer edge of the disk , which is thought to be responsible for the optical light curve modulation . also , the shock of the in - falling stream can cause the disk to bulge outwards at smaller radii or cause the stream to be deflected upward and arc over the surface of the accretion disk ( e.g. * ? ? ? this can cause phase dependent absorption as colder material in the accretion stream moves in front of the continuum source . the additional absorption seen in z cam is qualitatively compatible with some sort of stream - disk interaction . the enhanced absorption is narrow and centered on the mean line profile , indicative of matter that is moving across , rather than parallel to the line of sight . there is no corresponding change in the ionization state and the increase in absorption affects those transitions that appear to be optically thick in the mean spectrum . this is consistent with a disk bulge or stream temporarily moving to occult a larger area of the continuum source , or to place a greater column density of absorbing ions into the line of sight . also , the 0.650.81 phasing is in the phase range that stream - overflow effects are thought to be seen . in these respects z cam compares well with the spectrum of u gem in outburst @xcite , which was observed to show strong enhanced absorption at phase 0.53 to 0.79 . the line variability in u gem is of a similar strength to that seen in z cam , i.e. residual line core flux reducing to as little as 40% of its mean value in some lines , with the o lines being the least affected , although the n@xmath13924 , c@xmath131176 and other weak lines participate in the variation in u gem . smooth particle hydrodynamical models of the disk - stream interaction are now being produced ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? these models make predictions of the observational qualities which we are now able to set against the evidence for stream - related variability seen in the spectrum of z cam . the models are generally in agreement that stream overflow can occur at low mass - accretion rates , i.e. quiescent disks . @xcite predict that efficient cooling of the hot - spot region can occur in systems with low mass - accretion rates ( @xmath77 , or @xmath78 ) , allowing material to overflow the inner disk in a coherent stream , whereas , in higher- systems the stream impact region tends to push the disk into a bulging shape . using a different method , @xcite concurs with armitage & livio that up to @xmath59% of the matter in the accretion stream from the secondary is able to overflow the disk . if the phase - dependent absorption is a result of stream - overflow , it may have implications for the estimated inclination of the system . logically , for absorption by the stream , the absorption strength should have a strong correlation with inclination angle . at higher inclinations , material above the disk plane presents a higher column density to the bright continuum regions , i.e. the wd and inner disk . @xcite estimate that in outburst , enhanced absorption can be seen in systems of inclinations down to 65 , based on the maximum scale height above the disk attained by material in the accretion stream . however , they predict that , at low , material is not as strongly deflected upward as for high and that an inclination angle of at least 75is needed before the overflowing stream can cause accretion dips . at an inclination of only @xmath79(as taken from * ? ? ? * ) , z cam would fall below this lower limit . furthermore , an inclination above the current upper limit of 68 for z cam would produce observable eclipses and therefore can be ruled out . however , given the similarity of the time - dependent absorption to that seen in u gem ( @xmath80 ) , an inclination angle near 68seems far more plausible that the opposite extreme of 48 .	the spectrum resembles that of a hot ( 57,000k ) metal - enriched white dwarf . a high effective temperature is consistent with the expectation that dwarf nova systems that show standstills , as z cam does , have higher than normal time - averaged mass accretion rates . it is also consistent with current estimates for the mass and distance to z cam . a white dwarf model in which 29% of the surface has a temperature of 72,000 k and the rest of the surface is at 26,000k also reproduces the spectral shape and the continuum flux level at the nominal distance and wd mass , and is a somewhat better statistical fit to the data .	we have obtained _ far ultraviolet spectroscopic explorer _ ( 9051187 ) spectra of the non - magnetic cataclysmic variable z cam during a period of quiescence . the spectrum resembles that of a hot ( 57,000k ) metal - enriched white dwarf . a high effective temperature is consistent with the expectation that dwarf nova systems that show standstills , as z cam does , have higher than normal time - averaged mass accretion rates . it is also consistent with current estimates for the mass and distance to z cam . a white dwarf model in which 29% of the surface has a temperature of 72,000 k and the rest of the surface is at 26,000k also reproduces the spectral shape and the continuum flux level at the nominal distance and wd mass , and is a somewhat better statistical fit to the data . a second component could be due to a rotating accretion belt , a remnant of an outburst that ended eleven days prior to the observation , or ongoing accretion . we favor the uniform temperature model for z cam , largely because the data do not require anything more complicated . we have compared the quiescent spectrum with an archival spectrum of z cam in standstill , obtained with . the standstill spectrum is described well by a disk accreting at = , where the errors depend on the assumed inclination . the quiescent spectra cover a full orbital period and are time - resolved tos . no variability was observed in the continuum during the observation , but the depth of many of the absorption lines increased between orbital phases 0.65 and 0.81 . we attribute this effect to absorption by material associated with the accretion stream , which is easier to understand if the inclination is near the maximum allowed value of 68 .
astro-ph0412501	c	we have obtained observations with the satellite of the dwarf nova , z cam , during a period of quiescence . the spectrum is characterized by a fairly flat continuum , with a peak in the flux at 1000 . the line spectrum covers a broad range of atomic species and ionization stages and is dominated by absorption lines of fwhm @xmath12 . qualitatively , the spectrum can be self - consistently described in terms of emission from the wd with a temperature of 57,000 k. modest improvements in the fits are obtained with 2 t models in which most of the emission comes from a small fraction ( 29% ) of the surface heated to @xmath81k . the remainder is at 26,300k . we favor the uniform temperature model for z cam , largely because the data do not require anything more complicated . there are emission lines ( e.g. c@xmath131176 ) that do not come from the wd . the widths of these lines are consistent with a disk origin . in the phase - resolved quiescent spectrum we have observed transient enhanced line absorption . from the 0.650.81 phasing of this absorption and its effect on a wide range of ionization species , we attribute it to material raised from the disk plane into the los , due to interaction of the accretion stream with the disk , or the stream itself moving over the disk . such effects may be easier to understand if inclination of z cam is close to the upper limit of 68 . the standstill continuum is best described by an optically - thick disk accreting at a rate of , depending on the actual inclination of z cam . the continuum slope and the line absorption spectra differ little between quiescence and standstill , despite that , during standstill , an accretion disk creates ( most of ) the continuum flux . the qualitative similarity of the two spectra highlights the difficulty of separating wd from disk signatures without detailed model fitting and , also , underlines the reliance of the model fits on an secure knowledge of the distance and the wd mass . the high temperature of the wd in z cam and the estimates of mass accretion rate in standstill and outburst are all consistent with a mass transfer rate from the secondary star that is higher than in normal dne . additional fuv observations of z cam in the period following a normal outburst are highly desirable both to better understand the physics of standstill systems and to cleanly distinguish between single and multi - temperature models of the wd in z cam . in this research , we have used , and acknowledge with thanks , data from the aavso international database , based on observations submitted to the aavso by variable star observers worldwide . we also gratefully acknowledge the financial support from nasa through grant nag 5 - 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& - & 163 & 6.7 & 672 + wd & 4.4 & 57,200 & 330 & - & 163 & 10.1 & 1146 + 2wd & 6.0 ( 71%/29% ) & 26,300/71,700 & 170/370 & - & 163 & 9.4 & 1146 + disk ( 46 ) & - & - & - & 6.6 & 163 & 32.1 & 1146 + disk ( 57 ) & - & - & - & 9.1 & 163 & 27.1 & 1146 + disk ( 68 ) & - & - & - & 12.9 & 163 & 22.0 & 1146 + disk ( 57 ) & - & - & - & 180.0 & 710 & 11.9 & 1146 + disk ( 46 ) & wd & 4.0 & 62,000 & 306 & 1.2 & 163 & 9.8 & 1146 + disk ( 57 ) & wd & 4.0 & 62,000 & 295 & 1.7 & 163 & 9.8 & 1146 + disk ( 68 ) & wd & 3.9 & 62,000 & 293 & 2.5 & 163 & 9.8 & 1146 + + wd & 6.0 & 44,600 & - & - & 163 & 8.2 & 471 + 2wd & 18.4(97%/3% ) & 17,600/82,400 & - & - & 163 & 4.9 & 471 + disk ( 46 ) & - & - & - & 6.0 & 163 & 11.1 & 471 + disk ( 57 ) & - & - & - & 8.7 & 163 & 9.6 & 471 + disk ( 68 ) & - & - & - & 12.9 & 163 & 8.1 & 471 + disk ( 57 ) & - & - & - & 182.0 & 710 & 5.8 & 471 + disk ( 46 ) & wd & 3.0 & 82,000 & - & 3.0 & 163 & 4.7 & 471 + disk ( 57 ) & wd & 3.0 & 81,000 & - & 4.0 & 163 & 5.0 & 471 + disk ( 68 ) & wd & 3.0 & 81,000 & - & 6.3 & 163 & 5.4 & 471 + + wd & 12.5 & 59,700 & 240 & - & 163 & 2.6 & 1505 + disk ( 46 ) & - & - & - & 43.0 & 163 & 2.7 & 1505 + disk ( 57 ) & - & - & - & 69.0 & 163 & 2.6 & 1505 + disk ( 68 ) & - & - & - & 112.0 & 163 & 2.5 & 1505 + disk ( 57 ) & - & - & - & 195.0 & 270 & 2.4 & 1505 + [ fits ] lcccc h ... & 930.748 & @xmath98 & @xmath99 + s ... & 933.4 & @xmath100 & @xmath101 + h ... & 937.8 & @xmath102 & @xmath103 + s ... & 944.5 & @xmath104 & @xmath105 + h + p ... & 949.7 & @xmath106 & @xmath107 + h ... & 972.5 & @xmath108 & @xmath109 + c ... & 977.0 & @xmath110 & @xmath111 + n + si * ... & 989.8 ; 993.5 & @xmath112 & @xmath113 + si * ... & 994.8 & @xmath114 & @xmath115 + si * ... & 997.4 & @xmath116 & @xmath117 + s ... & 1012.5 & @xmath96 & @xmath115 + s ... & 1015.5 & @xmath96 & @xmath115 + s ... & 1021.1 & @xmath118 & @xmath119 + ... & 1025.7 & @xmath120 & @xmath121 + o ... & 1031.9 & @xmath122 & @xmath123 + o ... & 1037.6 & @xmath124 & @xmath125 + s ... & 1062.7 & @xmath126 & @xmath127 + s ... & 1073.0 & @xmath128 & @xmath129 + he * + n ... & 1084.9 ; 1085.0 & @xmath130 & @xmath131 + si * ... & 1108.4 ; 1110.0 & @xmath132 & @xmath133 + si * ... & 1113.2 & @xmath134 & @xmath135 + p ... & 1118.0 & @xmath136 & @xmath137 + si * ... & 1122.5 & @xmath138 & @xmath139 + p + si * ... & 1128.0 ; 1128.3 & @xmath120 & @xmath140 +	we have obtained _ far ultraviolet spectroscopic explorer _ ( 9051187 ) spectra of the non - magnetic cataclysmic variable z cam during a period of quiescence . we favor the uniform temperature model for z cam , largely because the data do not require anything more complicated . the standstill spectrum is described well by a disk accreting at = , where the errors depend on the assumed inclination . we attribute this effect to absorption by material associated with the accretion stream , which is easier to understand if the inclination is near the maximum allowed value of 68 .	we have obtained _ far ultraviolet spectroscopic explorer _ ( 9051187 ) spectra of the non - magnetic cataclysmic variable z cam during a period of quiescence . the spectrum resembles that of a hot ( 57,000k ) metal - enriched white dwarf . a high effective temperature is consistent with the expectation that dwarf nova systems that show standstills , as z cam does , have higher than normal time - averaged mass accretion rates . it is also consistent with current estimates for the mass and distance to z cam . a white dwarf model in which 29% of the surface has a temperature of 72,000 k and the rest of the surface is at 26,000k also reproduces the spectral shape and the continuum flux level at the nominal distance and wd mass , and is a somewhat better statistical fit to the data . a second component could be due to a rotating accretion belt , a remnant of an outburst that ended eleven days prior to the observation , or ongoing accretion . we favor the uniform temperature model for z cam , largely because the data do not require anything more complicated . we have compared the quiescent spectrum with an archival spectrum of z cam in standstill , obtained with . the standstill spectrum is described well by a disk accreting at = , where the errors depend on the assumed inclination . the quiescent spectra cover a full orbital period and are time - resolved tos . no variability was observed in the continuum during the observation , but the depth of many of the absorption lines increased between orbital phases 0.65 and 0.81 . we attribute this effect to absorption by material associated with the accretion stream , which is easier to understand if the inclination is near the maximum allowed value of 68 .
astro-ph0304371	i	galaxies in dense clusters evolve mainly due to tidal interactions , mergers and ram pressure stripping with accretion contributing to the buildup of the cd galaxies that often reside at the bottom of the cluster potential ( dressler 1984 ) . these processes are expected to be most effective in the cluster cores where higher densities will lead to more efficient ram pressure stripping and tidal effects should be stronger . indeed , observations of in abell 2029 failed to detect emission - line galaxies projected within 600 kpc of the center of the cluster , with the exception of a background galaxy , whereas two - thirds of the galaxies located outside this radius were detected ( dale & uson 2000 ) . it is well established that galaxies in clusters tend to be deficient in their neutral hydrogen ( ) emission ( e.g. haynes , giovanelli & chincarini 1984 ) . more recently , solanes et al . ( 2001 ) analyzed a sample of 1900 galaxies in the fields of eighteen nearby clusters ( @xmath7 ) and found that deficient galaxies are more likely located near the cluster cores . this trend holds true in abell 2670 , which is one of the most distant clusters to be imaged in neutral hydrogen ( @xmath8 , van gorkom 1996 ) . a truly extreme case is that of abell 2029 which is at the same redshift as abell 2670 but in which a deeper search for by one of us ( jmu ) resulted in an order of magnitude lower detection rate . deficiency in cluster galaxies is usually attributed to ram pressure stripping : as galaxies approach the central regions of clusters at a speed @xmath9 , they experience a strong interstellar - gas intracluster - gas interaction which is proportional to @xmath10 . this interaction is likely to induce a burst of star formation and subsequently strip away most of the the remaining galactic interstellar gas ( fujita 1998 ; fujita & nagashima 1999 ; balogh et al . 1999 ; quilis , moore & bower 2000 ) . new results from the sloan digital sky survey show cluster effects that can not be reconciled by the morphology - density relation alone . using a volume - limited sample of 8598 galaxies with @xmath11 , gomez et al . ( 2003 ) find that the galaxy star formation rate decreases with increasing galaxy density . in a study of the rotation curves of 510 galaxies in 53 clusters spread throughout @xmath12 , dale et al . ( 2001 ) found support for this galaxy - cluster interaction scenario in the normalized radial extent of emission in cluster spiral galaxies : it increases 4@xmath132% per mpc of ( projected ) separation of the galaxy from the cluster - core . analysis of the kinematical asymmetries of the galaxies also shows a trend with cluster - centric distance rotation curve asymmetry is greater by a factor of two for inner cluster early - type spiral galaxies . these two results lead these authors to claim that _ `` such trends are consistent with spiral disk perturbations or even the stripping of the diffuse , outermost gaseous regions within the disks as galaxies pass through the dense cluster cores '' _ ( dale et al . 2001 ) . are such observables different in @xmath14 clusters ? are they different for richer , more x - ray luminous clusters , thus solidifying the interpretation that the intracluster environment can significantly impact galaxy evolution in clusters ? in an effort to explore the tully - fisher relation at @xmath5 , we have undertaken a new imaging and spectroscopic campaign of four rich abell clusters : abell 1413 , abell 2029 , abell 2218 , and abell 2670 . results from the first cluster surveyed , abell 2029 , were presented in dale & uson ( 2000 ) . here , we present a full analysis of the data for all four clusters . we also include results from abell 2295 , the only @xmath8 cluster observed in the dale et al . ( 1999 ) survey .	we have obtained new optical imaging and spectroscopic observations of 78 galaxies in the fields of the rich clusters abell 1413 ( ) , abell 2218 ( ) and abell 2670 ( ) . we have combined these data with our previous observations of abell 2029 and abell 2295 ( both at ) , which yields a sample of 156 galaxies .	we have obtained new optical imaging and spectroscopic observations of 78 galaxies in the fields of the rich clusters abell 1413 ( ) , abell 2218 ( ) and abell 2670 ( ) . we have detected line emission from 25 cluster galaxies plus an additional six galaxies in the foreground and background , a much lower success rate than what was found (% ) for a sample of 52 lower - richness abell clusters in the range . we have combined these data with our previous observations of abell 2029 and abell 2295 ( both at ) , which yields a sample of 156 galaxies . we evaluate several parameters as a function of cluster environment : tully - fisher residuals , equivalent width , and rotation curve asymmetry , shape and extent . although is more easily detectable in galaxies that are located further from the cluster cores , we fail to detect a correlation between extent and galaxy location in those where it is detected , again in contrast with what is found in the clusters of lesser richness . we fail to detect any statistically significant trends for the other parameters in this study . the zero - point in the tully - fisher relation is marginally fainter ( by 1.5 ) than that found in nearby clusters , but the scatter is essentially unchanged .
astro-ph0304371	c	the goal of this survey is to investigate the impact that the intracluster medium has on galaxies residing in a range of cluster environments at @xmath94 . a total of 156 galaxies were observed spectroscopically in five clusters ranging from rich , x - ray luminous systems to richness class 0 clusters undetected in x - rays . about half of the sample ( 45% ) was detected in . we observe no significant trend in the extent of emission as a function of cluster - centric distance . this is in sharp contrast to what is observed in the nearby cluster sample , particularly when the projected cluster - centric distance is expressed in units of @xmath66 . we also fail to detect significant trends in rotation curve asymmetry , @xmath43 band tully - fisher residuals , rotation curve shape , and equivalent width . the relatively small number of rotation curves obtained for the dense clusters might be the main reason for our inability to detect statistically significant trends with cluster richness or location within the clusters . however , it is also possible that the low detection rate is a consequence of ram pressure stripping of the galaxies as they traverse the cores of the clusters , so that the galaxies that we do detect in would have avoided the cluster cores irrespective of their projected cluster - centric separation . indeed , a vla study of abell 2670 found @xmath95 sources , but _ none _ within 0.5 mpc of the cluster center ( van gorkom 1996 ) . but a deep vla survey of abell 2029 , sensitive to a 5@xmath6 mass of @xmath96 m@xmath97 within 1.5 mpc of the cluster center , has detected only three sources ( uson , in preparation ) . there is a clear difference in the cluster - centric distribution of actively star - forming and quiescent galaxies , with the star - forming galaxies preferentially found more in the cluster peripheries . this result is perhaps not surprising , given that the well - known cluster morphology - density relation likely contributes to this effect . although ground - based imaging precluded perfect sample selection , we strived to only observe spiral galaxies . moreover , as can be seen in figure [ fig : env ] , our sample selection appears to have been skewed towards late - type spirals near the cluster cores . thus , if the morphology - density relation has contributed to our observed distribution of strong and weak emitters , our sample selection seems to have minimized its impact . the zero - point in the @xmath5 @xmath43 band tully - fisher relation ( equation [ eq : tfhighz ] ) is a bit fainter ( by 1.5@xmath6 ) than that observed for nearby clusters ( equation [ eq : tflowz ] ) . the data for abell 2218 , even more distant at @xmath19 , are an additional 1.8@xmath6 fainter than the @xmath5 template . are these discrepancies related to the comparatively high redshift of the clusters ? is this discrepancy evidence of evolution or observational biases ? it is unclear whether or not the difference is due to systematic effects in the observational program : though seeing effects push deprojected rotational velocity widths to artificially high values , `` slit smearing '' of the disk rotation profile conversely biases the widths low . in case the correction recipes applied are unfit at this relatively high redshift , the simulations and empirical prescriptions used to generate the correction recipes have been revisited . for example , dale et al . ( 1997 ) have calibrated the effects of seeing on the inferred inclinations . they found a linear relation between the circularization of isophotes and the ratio of the seeing full - width half - maximum to face - on disk scale length @xmath98 : _ true/_obs = 1 + 0.118 , where @xmath99 and @xmath100 are the `` intrinsic '' and `` observed '' disk ellipticities . however , they only tested this relation for galaxies observed out to @xmath36 . using a separate technique from that explored in dale et al . ( 1997 ) , we are able to both reproduce the seeing correction of dale et al . ( 1997 ) over their sample s @xmath101 redshift range , and find that it is applicable even for galaxies as distant as those in abell 2218 . in the simulations artificial , inclined disk galaxies ( created using mkobjects in the artdata package of iraf ) are progressively smoothed such that they exhibit increasingly circular isophotes . isophotal ellipses are fit to the simulated galaxies using the same techniques used for the observed galaxies . the relation first quantified by dale et al . ( 1997 ) tends to non - linearity only when @xmath98 exceeds 2.0 , and all of the galaxies observed in abell 2218 have this ratio less than 1.8 . both the total and intrinsic scatter of the @xmath43 band tully - fisher relation at @xmath14 are similar to that in nearby clusters . the total scatter is comparable to that found in giovanelli et al . ( 1997 ) and dale et al . ( 1999 ) : 0.35 and 0.38 mag , respectively . the intrinsic scatter in the tully - fisher relation is the portion that can not be reconciled by measurement uncertainties . this parameter presumably reflects the various feedback mechanisms and range of parameter space involved in galaxy formation . andersen et al . ( 2001 ) suggest that perhaps up to half of the intrinsic scatter can be accounted for if disk galaxies simply have an average inherent ellipticity of 0.05 , a value they find for their sample of seven nearly face - on spiral galaxies . compared to the @xmath102 mag intrinsic scatter found by dale et al . ( 1999 ) in clusters at lower redshifts , there is no significant difference in the intrinsic @xmath43 band tully - fisher scatter in these four clusters at @xmath5 . in short , no significant evolution in the @xmath43 band tully - fisher properties of cluster galaxies appears to have occurred since @xmath14 . we are grateful for the assistance richard cool provided in preliminary explorations for correlations with cluster x - ray data . we thank steve boughn for his permission to use the unpublished _ i_-band observations of abell 2029 and abell 2218 and heinz andernach for his insight on the redshifts of abell 2218 . the comments of the referee helped to improve the presentation of this work . the results presented in this paper are based on observations carried out at the palomar observatory ( po ) and at the kitt peak national observatory ( kpno ) . the hale telescope at the po is operated by the california institute of technology under a cooperative agreement with cornell university and the jet propulsion laboratory . kpno is operated by the association of universities for research in astronomy , inc . , under a cooperative agreement with the national science foundation . this research has made use of the nasa / ipac extragalactic database ( ned ) which is operated by the jet propulsion laboratory , california institute of technology , under contract with nasa , and the image reduction and analysis facility ( iraf ) which is distributed by the national optical astronomy observatories , which are operated by the association of universities for research in astronomy , inc . , under a cooperative agreement with the national science foundation . the nrao is a facility of the national science foundation which is operated under cooperative agreement by associated universities , inc . the digitized sky surveys were produced at the space telescope institute under u.s . government grant nag w-2166 . the images of these surveys are based on photographic data obtained using the oschin schmidt telescope on palomar mountain and the uk schmidt telescope . dum abell , g. o. 1958 , , 3 , 211 andersen , d. r. , bershady , m. a. , sparke , l. s. , gallagher iii , j. s. & wilcots , e.m . 2001 , , 551 , l131 balogh , m. l. , schade , d. , morris , s. l. , yee , h. k. c. , carlberg , r. g. , & ellingson , e. 1998 , , 504 , l75 balogh , m. l. , morris , s. l. , yee , h. k. c. , carlberg , r. g. & ellingson , e. 1999 , , 527 , 54 balogh m. l. , couch , w. j. , smail , i. , bower , r. g. & glazebrook , k. 2002 , , 335 , 10 bird , c. 1994 , , 422 , 480 boughn , s. p. , uson , j. m. , blount , c. d. & gupta , g. 2000 , , 32 , 1499 carlberg , r. g. , yee , h. k. c. & ellingson , e. 1997 , , 478 , 462 conselice , c. j. & gallagher iii , j. s. 1999 , , 117 , 75 dale , d. a. , giovanelli , r. , haynes , m. p. , scodeggio , m. , hardy , e. & campusano , l. 1997 , , 114 , 455 dale , d. a. , giovanelli , r. , haynes , m. p. , scodeggio , m. , hardy , e. & campusano , l. 1998 , , 115 , 418 dale , d. a. 1998 , ph.d . thesis , cornell university dale , d. a. , giovanelli , r. , haynes , m. p. , hardy , e. & campusano , l. 1999 , , 118 , 1489 dale , d. a. & uson , j. m. 2000 , , 120 , 552 dale , d. a. , giovanelli , r. , haynes , m. p. , hardy , e. & campusano , l. 2001 , , 121 , 1886 dressler , a. 1978 , , 226 , 55 dressler , a. 1984 , , 22 , 185 dressler , a. , oemler jr . , a. , couch , w. j. , smail , i. , ellis , r. s. , barger , a. j. , butcher , h. , poggianti , b. m. & sharples , r. m. 1997 , , 490 , 577 ebeling , h. , edge , a. c. , fabian , a. c. , allen , s. w. , crawford , c. s. & bhringer h. 1997 , , 479 , l101 fujita , y. 1998 , , 509 , 587 fujita , y. & nagashima , m. 1999 , , 516 , 619 gavazzi , g. , boselli , a. , pedotti , p. , gallazzi , a. & carrasco , l. 2002 , , 396 , 449 giovanelli , r. , haynes , m. p. , herter , t. , vogt , n. p. , da costa , l. n. , freudling , w. , salzer , j. j. & wegner , g. 1997 , , 113 , 53 gomez , p.l . , nichol , r.c . , miller , c.j . et al . 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gmez , c. , gonzlez - casado , g. , giovanelli , r. & haynes , m. p. 2001 , , 548 , 97 swaters , r. a. , schoenmakers , r. h. m. , sancisi , r. & van albada , t. s. 1999 , , 304 , 330 uson , j. m. , boughn , s. p. & kuhn , j. r. 1991 , , 369 , 46 van gorkom , j. h. 1996 , in _ the minnesota lectures on extragalactic hydrogen _ , ed . e. d. skillman , asp conference series , vol . 106 , p. 293 whitmore , b. c. , forbes , d. a. & rubin , v. c. 1988 , , 333 , 542 ziegler , b. l. , bower , r. g. , smail , i. , davies , r. l. & lee , d. 2001 , , 325 , 1571 ccccccclccc a1413 & 115248 & @xmath103233900 & 226,@xmath10377 & 42453570 & 42767 & 1490 & 9 & 10.30.5 & 4.5 + a2029 & 150830 & @xmath103055700 & 7,@xmath10351 & 23220170 & 23400 & 1471 & 92 & 16.40.6 & 4.4 + a2218 & 163542 & @xmath103661900 & 98,@xmath10338 & 52514170 & 52497 & 1437 & 93 & 9.30.4 & 4.3 + a2295 & 180018 & @xmath103691300 & 99,@xmath10330 & 24623200 & 24555 & 563 & 9 & @xmath1040.1 & 0 + a2670 & 235136 & @xmath105104100 & 81,@xmath10569 & 22841 60 & 22494 & 895 & 235 & 2.00.1 & 1.4 + [ tab : cluster_sample ] llcccccc 1999 apr 20 - 21 & a2218 & 0.7 & 1 & 1/ 8 & 1.52 & 72507920 & 30,30062,100 + 1999 may 14 & a2218 & 1 & 3 & 4/11 & 1.52.5 & 73308000 & 33,50065,700 + 1999 oct 31-nov 1 & a2670 & 2 & 16 & 15/28 & 1.52 & 67807450 & 9,80040,300 + 2001 may 20 - 21 & a1413,a2218 & 2 & 7 & 12/31 & 1.52.5 & 73308000 & 33,50065,700 + [ tab : spec_runs ] a1413 - 211894 & 115208.1 & @xmath103233828 & ... & 0 & a2218 - 261717 & 163612.6 & @xmath103663031 & 52378 & 1 + a1413 - 211903 & 115216.8 & @xmath103235549 & ... & 0 & a2218 - 261274 & 163618.1 & @xmath103662436 & ... & 0 + a1413 - 211916 & 115228.0 & @xmath103235115 & ... & 0 & a2218 - 261718 & 163644.7 & @xmath103661913 & 51601 & 1 + a1413 - 211924 & 115238.6 & @xmath103235007 & 42900 & 2 & a2218 - 261719 & 163647.4 & @xmath103661425 & ... & 0 + a1413 - 211934 & 115243.6 & @xmath103234059 & 42844 & 0 & a2218 - 261720 & 163647.5 & @xmath103662135 & 54557 & 2 + a1413 - 211938 & 115244.8 & @xmath103234332 & ... & 0 & a2218 - 261286 & 163650.7 & @xmath103662455 & ... & 0 + a1413 - 211956 & 115301.1 & @xmath103234748 & ... & 0 & a2218 - 261721 & 163658.6 & @xmath103660743 & ... & 0 + a1413 - 211957 & 115301.6 & @xmath103234725 & 41400 & 2 & a2218 - 261289 & 163700.4 & @xmath103661548 & ... & 0 + a1413 - 211968 & 115331.3 & @xmath103235648 & ... & 0 & a2218 - 261290 & 163705.2 & @xmath103661137 & ... & 0 + a2218 - 261222 & 163237.5 & @xmath103662428 & ... & 0 & a2218 - 261723 & 163752.9 & @xmath103661412 & ... & 0 + a2218 - 261223 & 163248.0 & @xmath103661744 & 56018 & 1 & a2218 - 261291 & 163755.8 & @xmath103662815 & 51553 & 1 + a2218 - 261702 & 163250.8 & @xmath103660732 & ... & 0 & a2670 - 630560 & 235008.6 & @xmath105110012 & 22883 & 0 + a2218 - 261224 & 163255.6 & @xmath103663400 & ... & 0 & a2670 - 630563 & 235024.5 & @xmath105105752 & 21810 & 1 + a2218 - 261703 & 163302.7 & @xmath103661240 & ... & 0 & a2670 - 630565 & 235031.5 & @xmath105105736 & 21948 & 1 + a2218 - 261704 & 163314.2 & @xmath103662632 & ... & 0 & a2670 - 630567 & 235034.8 & @xmath105110058 & 22561 & 1 + a2218 - 261705 & 163318.4 & @xmath103662500 & 55706 & 1 & a2670 - 630568 & 235034.9 & @xmath105104620 & 22892 & 1 + a2218 - 261706 & 163340.0 & @xmath103660322 & ... & 0 & a2670 - 630570 & 235044.7 & @xmath105103449 & 22607 & 0 + a2218 - 261226 & 163421.0 & @xmath103662518 & 52793 & 1 & a2670 - 630571 & 235044.9 & @xmath105103944 & 22291 & 2 + a2218 - 261708 & 163456.9 & @xmath103663036 & ... & 0 & a2670 - 630574 & 235053.7 & @xmath105104718 & 21843 & 0 + a2218 - 261709 & 163502.8 & @xmath103661355 & ... & 0 & a2670 - 630577 & 235111.6 & @xmath105105034 & 23501 & 1 + a2218 - 261244 & 163518.8 & @xmath103662121 & 42855 & 1 & a2670 - 630584 & 235124.6 & @xmath105105820 & 23662 & 0 + a2218 - 261245 & 163523.0 & @xmath103661938 & ... & 0 & a2670 - 630585 & 235126.2 & @xmath105103826 & 23757 & 0 + a2218 - 261247 & 163524.0 & @xmath103662003 & ... & 0 & a2670 - 630318 & 235129.7 & @xmath105103642 & 20968 & 0 + a2218 - 261710 & 163524.6 & @xmath103661204 & ... & 0 & a2670 - 630317 & 235130.4 & @xmath105104231 & 21597 & 1 + a2218 - 261248 & 163527.3 & @xmath103662630 & ... & 0 & a2670 - 630319 & 235132.2 & @xmath105104208 & 22380 & 0 + a2218 - 261711 & 163529.1 & @xmath103662719 & 52572 & 1 & a2670 - 630588 & 235134.1 & @xmath105105129 & 22562 & 1 + a2218 - 261251 & 163530.2 & @xmath103661213 & ... & 0 & a2670 - 630322 & 235139.2 & @xmath105103951 & 23398 & 0 + a2218 - 261712 & 163531.1 & @xmath103660345 & 37100 & 2 & a2670 - 630593 & 235139.5 & @xmath105104006 & 23924 & 1 + a2218 - 261252 & 163532.9 & @xmath103662302 & ... & 0 & a2670 - 630324 & 235142.6 & @xmath105103136 & 22674 & 0 + a2218 - 261713 & 163538.9 & @xmath103661645 & 53500 & 2 & a2670 - 630597 & 235143.0 & @xmath105104138 & 24556 & 0 + a2218 - 261259 & 163539.5 & @xmath103661912 & ... & 0 & a2670 - 630599 & 235144.0 & @xmath105104136 & 23128 & 0 + a2218 - 261714 & 163545.7 & @xmath103661000 & ... & 0 & a2670 - 630600 & 235144.2 & @xmath105103031 & 23229 & 1 + a2218 - 261265 & 163550.3 & @xmath103661751 & 54862 & 0 & a2670 - 630328 & 235153.3 & @xmath105103855 & 22918 & 0 + a2218 - 261715 & 163554.1 & @xmath103661404 & 39100 & 2 & a2670 - 630607 & 235153.3 & @xmath105104040 & 27928 & 1 + a2218 - 261268 & 163556.3 & @xmath103662422 & 53852 & 1 & a2670 - 630615 & 235210.2 & @xmath105103337 & 23141 & 1 + a2218 - 261269 & 163600.5 & @xmath103661742 & ... & 0 & a2670 - 630621 & 235226.9 & @xmath105102654 & 23605 & 0 + a2218 - 261271b & 163602.1 & @xmath103662726 & 55300 & 2 & a2670 - 630624 & 235242.7 & @xmath105110249 & 13010 & 1 + a2218 - 261271 & 163604.4 & @xmath103662730 & ... & 0 & a2670 - 630625 & 235246.9 & @xmath105103855 & 22361 & 1 + a2218 - 261272 & 163611.9 & @xmath103661725 & ... & 0 & a2670 - 630627 & 235255.7 & @xmath105102030 & 12640 & 2 + [ tab : galaxy_sample ] crcccc a2218 - 261223 & 3900 & 5600307 & 397 & 70 & 37021 + a2218 - 261705 & 4800 & 5569007 & 538 & 60 & 53027 + a2218 - 261226 & 4500 & 5277710 & 300 & 58 & 35428 + a2218 - 261244 & 900 & 4283814 & 427 & 69 & 41324 + a2218 - 261711 & 4800 & 5255507 & 426 & 69 & 40922 + a2218 - 261268 & 5700 & 5383510 & 402 & 64 & 38226 + a2218 - 261717 & 4500 & 5236007 & 367 & 65 & 35023 + a2218 - 261718 & 6300 & 5158310 & 305 & 66 & 29923 + a2218 - 261291 & 3300 & 5153408 & 398 & 57 & 44125 + a2670 - 630563 & 3600 & 2146310 & 372 & 53 & 45033 + a2670 - 630565 & 900 & 2160110 & 342 & 66 & 37223 + a2670 - 630567 & 1800 & 2221510 & 528 & 70 & 52125 + a2670 - 630568 & 2400 & 2254510 & 453 & 79 & 45422 + a2670 - 630571 & 1200 & 2194410 & 131 & 54 & 15431 + a2670 - 630577 & 2400 & 2315410 & 390 & 61 & 42223 + a2670 - 630317 & 1200 & 2125010 & 323 & 63 & 35227 + a2670 - 630588 & 2400 & 2221510 & 292 & 79 & 35443 + a2670 - 630593 & 900 & 2357710 & 338 & 71 & 41345 + a2670 - 630600 & 3600 & 2288210 & 443 & 90 & 43221 + a2670 - 630607 & 600 & 2758110 & 427 & 72 & 48626 + a2670 - 630615 & 3000 & 2279410 & 316 & 64 & 36345 + a2670 - 630624 & 300 & 1266410 & 123 & 42 & 19737 + a2670 - 630625 & 4200 & 2201410 & 451 & 70 & 49533 + a2670 - 630627 & 600 & 1229310 & 204 & 67 & 22223 + [ tab : spec ] crrrccccc a2218 - 261223 & 3 : & 18 & 7 & 0.6130.049 & 2.2 & 6.0 & 17.35 & -21.390.07 + a2218 - 261705 & 2 : & 16 & 100 & 0.4640.033 & 1.4 & 4.4 & 17.06 & -21.670.09 + a2218 - 261226 & 1 & 10 & 17 & 0.4320.043 & 1.3 & 4.0 & 17.75 & -20.860.10 + a2218 - 261244 & 2 & 3 & 18 & 0.5960.064 & 4.2 & 8.5 & 16.32 & -21.840.10 + a2218 - 261711 & 3 : & 8 & 0 & 0.5810.040 & 1.2 & 3.7 & 17.72 & -20.880.06 + a2218 - 261268 & 5 & 6 & 114 & 0.5400.063 & 1.6 & 5.8 & 17.25 & -21.350.07 + a2218 - 261717 & 3 & 12 & 45 & 0.5350.040 & 1.8 & 5.0 & 17.50 & -21.100.06 + a2218 - 261718 & 6 & 6 & 175 & 0.5660.058 & 1.0 & 3.8 & 17.75 & -20.850.09 + a2218 - 261291 & 2 : & 16 & 67 & 0.4270.021 & 1.1 & 3.6 & 17.59 & -20.970.09 + a2670 - 630563 & 4 & 24 & 130 & 0.3970.042 & 4.3 & 13.0 & 14.66 & -22.000.05 + a2670 - 630565 & 5 & 23 & 83 & 0.5830.036 & 4.0 & 12.0 & 14.82 & -21.850.05 + a2670 - 630567 & 3 & 25 & 135 & 0.5650.048 & 4.3 & 14.3 & 14.95 & -21.780.07 + a2670 - 630568 & 2 & 16 & 159 & 0.7230.045 & 3.2 & 9.8 & 15.18 & -21.580.14 + a2670 - 630571 & 4 & 13 & 43 & 0.2060.112 & 3.3 & 10.8 & 15.12 & -21.640.07 + a2670 - 630577 & 5 & 11 & 51 & 0.4910.025 & 2.6 & 7.7 & 15.02 & -21.740.04 + a2670 - 630317 & 5 & 2 & 105 & 0.6220.063 & 2.0 & 7.2 & 15.39 & -21.370.05 + a2670 - 630588 & 5 & 11 & 97 & 0.7600.009 & 2.9 & 9.6 & 15.25 & -21.510.10 + a2670 - 630593 & 7 & 1 & 110 & 0.6430.037 & 2.3 & 8.1 & 14.88 & -21.880.05 + a2670 - 630600 & 2 : & 11 & 138 & 0.8040.015 & 4.7 & 14.6 & 15.05 & -21.710.14 + a2670 - 630607 & 5 & 4 & 145 & 0.6640.018 & 3.2 & 9.2 & 15.50 & -21.700.05 + a2670 - 630615 & 3 : & 11 & 151 & 0.5430.057 & 5.4 & 15.0 & 15.31 & -21.450.07 + a2670 - 630624 & 7 & 27 & 115 & 0.2550.040 & 2.1 & 7.0 & 15.86 & -19.650.09 + a2670 - 630625 & 3 & 18 & 86 & 0.5400.099 & 2.7 & 8.9 & 14.84 & -21.920.08 + a2670 - 630627 & 1 : & 28 & 80 & 0.5720.043 & 5.7 & 14.5 & 14.65 & -20.800.10 + [ tab : phot ] cccccccc @xmath5 clusters & 70 of 156 & 0.47 & 0.36 & 12.61.2&11.11.2&1.180.07&15.92.7 + @xmath106 sbc & & & & 10.91.3&10.42.1&1.290.09&12.72.8 + @xmath107 sb & & & & 13.81.7&11.61.5&1.100.09&17.94.0 + @xmath108 clusters & 582 of 897 & 0.75 & & 14.00.4&10.10.4&1.110.02 & + field & & & & 12.51.0&10.61.1&1.180.04&22.81.3 + [ tab : results ] ccccccc a2029 & 14 & @xmath1050.100 & @xmath1050.0520.157 & 0.53 ( 0.34 ) & 23400 & @xmath1035501700 + a2218 & 8 & @xmath1030.237 & @xmath1030.2510.138 & 0.34 ( 0.29 ) & 52497 & @xmath10564003300 + a2295 & 10 & @xmath1050.042 & @xmath1050.0260.137 & 0.38 ( 0.32 ) & 24555 & @xmath1032901500 + a2670 & 11 & @xmath1030.003 & @xmath1030.0120.116 & 0.32 ( 0.17 ) & 22494 & @xmath1051201200 + [ tab : tf_results ]	we evaluate several parameters as a function of cluster environment : tully - fisher residuals , equivalent width , and rotation curve asymmetry , shape and extent . although is more easily detectable in galaxies that are located further from the cluster cores , we fail to detect a correlation between extent and galaxy location in those where it is detected , again in contrast with what is found in the clusters of lesser richness . we fail to detect any statistically significant trends for the other parameters in this study . the zero - point in the tully - fisher relation is marginally fainter ( by 1.5 ) than that found in nearby clusters , but the scatter is essentially unchanged .	we have obtained new optical imaging and spectroscopic observations of 78 galaxies in the fields of the rich clusters abell 1413 ( ) , abell 2218 ( ) and abell 2670 ( ) . we have detected line emission from 25 cluster galaxies plus an additional six galaxies in the foreground and background , a much lower success rate than what was found (% ) for a sample of 52 lower - richness abell clusters in the range . we have combined these data with our previous observations of abell 2029 and abell 2295 ( both at ) , which yields a sample of 156 galaxies . we evaluate several parameters as a function of cluster environment : tully - fisher residuals , equivalent width , and rotation curve asymmetry , shape and extent . although is more easily detectable in galaxies that are located further from the cluster cores , we fail to detect a correlation between extent and galaxy location in those where it is detected , again in contrast with what is found in the clusters of lesser richness . we fail to detect any statistically significant trends for the other parameters in this study . the zero - point in the tully - fisher relation is marginally fainter ( by 1.5 ) than that found in nearby clusters , but the scatter is essentially unchanged .
astro-ph0303275	i	we have presented high - sensitivity images of the isolated , edge - on , ` superthin ' spiral galaxy ugc 7321 with a resolution of 24.4 khz and a total bandwidth of 3.052 mhz ( 125 channels ) . in the optical , ugc 7321 exhibits a diffuse stellar disk with little dust obscuration , an extremely small global scale height , and no discernible spheroid component . these features indicate that ugc 7321 is a late - type , lsb spiral seen at high inclination . ugc 7321 thus allows us to explore both the radial and vertical structure of the ism of an ordinary lsb galaxy whose disk has not been recently perturbed . ugc 7321 shows similar global characteristics to other late - type , lsb spirals : it has a gas - rich disk with = @xmath77 d@xmath175 , and an inferred ratio of @xmath6 = 1.0(in solar units ) , which is at the high end of the observed values for spiral galaxies . assuming a stellar mass - to - light ratio similar to the sun ( based on its global @xmath103 color ) ugc 7321 contains a similar fraction of its visible mass in gas as in stars , suggesting that it has been a relatively inefficent star former . ugc 7321 is undetected in the 21-cm radio continuum ( @xmath9mjy ) , which is consistent with its status as a low star formation rate system . assuming a spherical mass distribution , the ratio of the dynamical mass to the total visible mass ( total gas+stars ) is @xmath176 , implying that ugc 7321 is a highly dark - matter dominated galaxy . to first order , the total- distribution of ugc 7321 is regular and symmetric with a slight depression near its center , and extends to approximately 1.5 times the stellar radius . the deprojected surface density is low ( peak value @xmath177 pc @xmath57 ) , which is consistent with other lsb spirals . the outer disk of ugc 7321 displays mild flaring in addition to an `` integral sign '' warp that commences near the edge of the stellar disk . the warped material bends back toward the equatorial plane in the outermost regions . the origin of this warp is still not understood , as ugc 7321 appears to be an isolated galaxy . the nearest known companions to ugc 7321 are two dwarf galaxies , both with projected distances of 0.34 d@xmath8 mpc and @xmath178 which would have had their last encounter with ugc 7321 @xmath93 years ago . in addition , the observations described in this paper rule out the presence of any close gas - rich companions with masses greater than 2.2@xmath179 ( @xmath180 ) within @xmath181 ( 36 d@xmath8 kpc ) . the disk of ugc 7321 appears thicker and more complex than what a single , cold layer confined to the midplane would display . however , the projection effects expected from warping and flaring of the gas layer have to be modelled in order to untangle the three - dimensional structure of the galaxy , which is complicated by its near - edge - on orientation . in addition , we detect filaments of gas extending to distances of up to @xmath1060@xmath0 ( 2.9 d@xmath8 kpc ) from the mid - plane in the total intensity images and in the position - velocity cuts along the minor axis of the disk , which suggests the presence of high - latitude gas . the position - velocity plot along the major axis of ugc 7321 displays a `` figure-8 '' pattern that we interpret as a manifestation of the warping of the disk . in addition , the diagram reveals the presence of a small bar or inner arm . overall ugc 7321 has a rather regular velocity field with only minor perturbations . similarly , the rotation curve of ugc 7321 exhibits only a mild asymmetry about the two sides of the disk . the rotation curve rises rather slowly and linearly throughout the stellar disk , indicating a low central matter density ; this effect can not be attributed to the finite spatial resolution of our observations . a peak rotational velocity of @xmath10110 is reached near 0.9 optical radii , and a slight decline in the rotation curve occurs in the last few measured points . two possible interpretations of this decline are that the dark matter halo of ugc 7321 is truncated near the edge of the disk or that we are seeing a projection effect due to the warping of the layer . @xmath132 ( j2000.0 ) & 12 17 33.8 @xmath182 ( j2000.0 ) & + 22 32 25 hubble type & sd iv distance ( mpc ) & 7 13 p. a. ( deg ) & @xmath183 inclination ( deg ) & @xmath184 @xmath185 & 10.3 @xmath186 ( arcmin ) & 5.6 @xmath186 ( kpc ) & 16.3 d@xmath8 @xmath187 ( kpc ) & @xmath188 d@xmath8 @xmath189 ( pc ) & @xmath190 d@xmath8	we have used the very large array to image the isolated `` superthin '' galaxy ugc 7321 in the line with a spatial resolution of 16 and a spectral resolution of 24 khz ( 5.2 ) . ugc 7321 has a gas - rich disk with d and ( d is the distance to ugc 7321 in units of 10 mpc , the value adopted in this paper ) , and no detectable radio continuum emission ( mjy ) . the global distribution of ugc 7321 is rather symmetric and extends to.5 times the optical radius ( at atoms ) . the ratio of the inferred dynamical mass to the mass in gas and stars is d , implying that ugc 7321 is a highly dark - matter dominated galaxy . 0.6truein 0.2truein	we have used the very large array to image the isolated `` superthin '' galaxy ugc 7321 in the line with a spatial resolution of 16 and a spectral resolution of 24 khz ( 5.2 ) . we have reached a sensitivity of ( 0.36 0.40 ) mjy / beam per channel , which correspond to a column density of ( 8 9) atoms ( ) . ugc 7321 has a gas - rich disk with d and ( d is the distance to ugc 7321 in units of 10 mpc , the value adopted in this paper ) , and no detectable radio continuum emission ( mjy ) . the global distribution of ugc 7321 is rather symmetric and extends to.5 times the optical radius ( at atoms ) . an `` integral sign '' warp is observed in the disk , commencing near the edge of the stellar distribution , and twisting back toward the equatorial plane in the outermost regions . in addition , the position - velocity diagram suggests the presence of a bar or inner arm within from the center . the rotation curve of ugc 7321 is slowly rising ; it reaches its asymptotic velocity of at from the center ( about 0.9 optical radii ) and declines near the edge of the disk . the ratio of the inferred dynamical mass to the mass in gas and stars is d , implying that ugc 7321 is a highly dark - matter dominated galaxy . 0.6truein 0.2truein
1409.8576	i	in many applications from a wide variety of fields , the data to be processed can partially ( or even almost completely ) be affected by severe noise in several phases , e.g. , occlusions during a visual recording or packet losses during transmission in a communication channel . the partial , i.e. , localized , corruptions resulted in the data due to such problems often severely degrade the performance of the target application ; for instance , face recognition or pedestrian detection under occlusion @xcite . in order to reduce the impact of this adverse effect , we develop a complete and novel framework , which efficiently detects , localizes and imputes corruptions by identifying the local anomalies in a given suspicious data instance . we emphasize that neither the existence nor , if exists , the location of a corruption is known in our framework . moreover , the proposed algorithms do not assume a model but operate in a data driven manner . we consider the local corruptions as statistical deviations from the nominal distribution of the uncorrupted ( clean ) observations . to detect and localize corruptions , i.e. , such statistical deviations , we model a corruption as an anomaly due to an external factor ( communication failure in a channel or occluder object in an image ) , which locally overwrites a data instance and moves it outside the support of the nominal distribution . however , corruptions that we consider as examples of anomalies have further specific properties such that ( a ) the corruptions in an instance are confined to unknown intervals along the data attributes , i.e. , localized , and ( b ) not only a corrupted part but also all of its subparts are anomalous . thus , a corruption does not provide an anomaly due to an incompatible combination of normal subparts . based on these properties that accurately model a wide variety of real life applications , we characterize the event of corruption and formulate the corresponding detection / localization as an anomaly detection problem , cf . @xcite . the introduced algorithm applies a series of statistical tests with a pre - specified false alarm rate to the parts of the suspicious instance after extracting the nominal statistics from a reference ( training ) data set of uncorrupted ( clean ) observations . as a result , each part is labeled as anomalous / normal and the local anomalies are identified . these parts are generated and organized through a binary tree partitioning of the data attributes , each node of which corresponds to a part of the suspicious instance . once the nodes ( or parts ) are labeled as anomalous / normal on this tree , the patterns of corruption are identified using the aforementioned characterization to detect and localize corruptions . we point out that this localization procedure transforms the nominal distribution into a multivariate bernoulli distribution with a success probability that precisely coincides with the constant false alarm rate of the local anomaly tests . considering the hierarchy among the binary labels implied by the tree as a directed acyclic graph , the resulting multivariate bernoulli distribution achieves a certain dependency structure . under this condition , we derive the false alarm rate of the proposed framework in detecting the corruptions and show that it is a constant rate , namely , no parameter tuning is required even if the data change . if a corruption is localized , then we impute / replace the affected attributes with the estimates of the underlying unknown true attributes . for this purpose , we additionally develop a novel _ maximum a posteriori _ ( map ) estimator using the score function " defined in @xcite . our estimator exploits the local dependencies among the data attributes , where the locality is encoded in the binary partitioning tree . we point out that the implementation of this map estimator does not load extra computational cost since it utilizes the outputs of our anomaly detection approach , which are computed prior to the imputation phase . furthermore , we also propose a novel distance measure named ranked euclidian distance " as a generalization to the standard euclidean distance , which is used in the course of the labeling of each part as anomalous / normal . the proposed distance measure is compared with the standard euclidean distance in the experiments and shown to be superior in terms of detecting and localizing corruptions . we conduct tests over several well - known machine learning data sets @xcite , which are exposed to severe data corruptions . our experiments indicate that the proposed framework achieves significant improvements after imputation up to @xmath0 in terms of the classification purposes and outperforms the typical approaches . the proposed algorithms are also empirically shown to be robust to varying training phase conditions with strong corruption separation capabilities . in this study , the corrupted attributes are considered to be statistically independent with the underlying unobserved true data , i.e. , corrupted attributes are of no use in estimation of the uncorrupted counterparts . hence , if one knows which attributes are corrupted in an instance , then those attributes can readily be treated as missing data , cf . @xcite . for example , classification and clustering with missing data is a well - studied problem in the machine learning literature . the corresponding studies such as @xcite are related to inference with incomplete data @xcite and generative models @xcite , where bayesian frameworks @xcite are used for inference under missing data conditions . alternatively , pseudo - likelihood @xcite and dependency network @xcite approaches solve data completion problem by learning conditional distributions . in @xcite , the probability density of the missing data is modeled conditioned on a set of introduced latent variables and thereafter , a map based inference is used . however , all of the studies @xcite either assume the knowledge of the location of the missing attributes or impose strong modeling constraints ; as opposed to the model free solutions in this paper . on the other hand , imputation is commonly used as a pre - processing tool @xcite . the mixture of factor analyzers @xcite approach replaces the missing attributes with samples drawn from a parametric density , which models the distribution of the underlying true data . the proposed imputation techniques in @xcite are , whereas , both non - parametric and based on the inference of the posterior densities via certain kernel expansions . on the contrary , the map estimator in this study does not even attempt to estimate the posterior density either in a parametric or non - parametric manner . instead , the introduced method is only based on the sufficient rank statistics . we emphasize that unlike our approach , the incomplete data approaches generally assume the knowledge of the missing attributes , i.e. , they are precisely localized and provided beforehand . for example , the occluded pixels in the event of occlusion of a target object in an image can not be known a priori , which requires a detection and localization step . since the existing studies do not have such a step , an exhaustive list of the occluded pixels as the result of a manual inspection of the missing attributes is required as an input to the algorithms proposed in the corresponding literature . in this regard , our study is the first to jointly handle the issues of detecting / localizing missing attributes , i.e. , corruptions , as well as their imputation in one complete framework . hence , the generic local corruption detection and imputation algorithm of our framework complements the missing data imputation approaches as an additional merit . data imputation and completion is also essential in image processing for handling corrupted images , e.g. , @xcite . generally , a corrupted image is restored by explicitly learning the image statistics @xcite or by using neural networks @xcite . these denoising studies do not attempt to localize corruptions in an image , but treat them as a noise and filter it out using statistical approaches applied to the image globally . even though this is a valid approach for image enhancement , an attempt to correct / enhance an image globally in case of only a localized corruption might be even detrimental since the uncorrupted parts are also affected by global operations . additionally , it is not usually possible to locally impute corrupted portions using denoising approaches . there exist several studies that aim localization as well . studies such as @xcite indicate that occlusion , as an example of corruption , is a common phenomenon and detrimental in pedestrian detection as well as face recognition applications . in this regard , detection of occluded , i.e. , corrupted , visual objects had been previously investigated in a number of studies @xcite . in these studies , occlusion detection is performed using domain specific knowledge ( visual cues ) or external information ( object geometry ) , which , however , are not always available in general data imputation setting . from the machine learning perspective , descriptors are extracted from various parts of the occluded object in @xcite and similarly ; part - based descriptors are weighted with the occlusion measure in @xcite to relieve the corresponding degrading effects . since these approaches do not directly target handling occlusions , i.e. , corruptions , they only provide partial or limited solutions . several other studies propose solutions via extracting occlusion maps , e.g. , @xcite . in @xcite , hog based classification errors ; and in @xcite , template based reconstruction errors are used to generate such an occlusion map . however , both studies assume rigid models and significantly rely on domain specific knowledge ; and in general fail to remain applicable if the data source belongs to another domain . in this study , we assume that data is generic and no domain information is available , yet detection and imputation of corruption is necessary for improving the subsequent processing stages , such as classification . 1 . this study is the first to jointly handle localized data corruptions in one statistical framework that is designed completely model free for the goal of separating a corruption and imputing the affected data attributes . we also provide a false alarm rate ( in detecting corruptions ) analysis of the framework via directed acyclic graphs . 2 . a novel map estimator for imputation and a novel distance measure for corruption localization purposes is proposed . the proposed framework is computationally efficient in the sense that ( i ) it effectively utilizes a binary search for corruption separation , and ( ii ) the computational load due to our map based imputation is insignificant . we propose a characterization for anomalies , e.g. , rarities , incompatible combinations and corruptions , which is a novel notion . + in section [ sec : pd ] , we provide the problem description . we then present our algorithm in section [ sec : thethemethod ] and the associated computational complexity in section [ sec : complexity ] . we report the corruption detection / localization performance of the proposed algorithm as well as the improvement in classification tasks achieved by the imputation in section [ sec : experiments ] . the paper concludes with a discussion in section [ sec : conclusion ] .	once each part is labeled as anomalous vs normal , the corresponding binary patterns over this tree that characterize corruptions are identified and the affected attributes are imputed . under a certain conditional independency structure assumed for the binary patterns , localized corruption , occlusion , map based imputation , anomaly detection .	we introduce a comprehensive and statistical framework in a model free setting for a complete treatment of localized data corruptions due to severe noise sources , e.g. , an occluder in the case of a visual recording . within this framework , we propose i ) a novel algorithm to efficiently separate , i.e. , detect and localize , possible corruptions from a given suspicious data instance and ii ) a _ maximum a posteriori _ ( map ) estimator to impute the corrupted data . as a generalization to euclidean distance , we also propose a novel distance measure , which is based on the ranked deviations among the data attributes and empirically shown to be superior in separating the corruptions . our algorithm first splits the suspicious instance into parts through a binary partitioning tree in the space of data attributes and iteratively tests those parts to detect local anomalies using the nominal statistics extracted from an uncorrupted ( clean ) reference data set . once each part is labeled as anomalous vs normal , the corresponding binary patterns over this tree that characterize corruptions are identified and the affected attributes are imputed . under a certain conditional independency structure assumed for the binary patterns , we analytically show that the false alarm rate of the introduced algorithm in detecting the corruptions is independent of the data and can be directly set without any parameter tuning . the proposed framework is tested over several well - known machine learning data sets with synthetically generated corruptions ; and experimentally shown to produce remarkable improvements in terms of classification purposes with strong corruption separation capabilities . our experiments also indicate that the proposed algorithms outperform the typical approaches and are robust to varying training phase conditions . localized corruption , occlusion , map based imputation , anomaly detection .
1409.8576	c	in this paper , we proposed a comprehensive framework for handling localized and severe data corruptions . the novel contributions of the proposed framework includes ( i ) a first algorithm to jointly detect and localize such corruptions by identifying the local anomalies , ( ii ) a _ maximum a posteriori _ based estimator for imputation ; and a distance measure for corruption separation purposes , ( iii ) computational efficiency via the binary searches and the fast imputations , and ( iv ) a characterization for anomalous observations , e.g. , rarities , incompatible combinations and corruptions . we point out that our algorithm does not assume prior information or a model for the input data and instead , works in a completely data driven way . furthermore , we conducted a false alarm rate analysis and showed that the desired false alarm rate in detecting corruptions can be set independently with the input data . our algorithm is tested against the synthetically generated corruptions in several well - known machine learning data sets and experimentally shown to provide signicant improvements in terms of classication purposes with strong corruption separation capabilities . the proposed algorithms outperform the typical approaches and are robust to varying training phase conditions . stefanos zafeiriou , georgios tzimiropoulos , maria petrou , and tania stathaki , `` regularized kernel discriminant analysis with a robust kernel for face recognition and verification , '' , vol . 3 , pp . 526534 , 2012 . roberto perdisci , guofei gu , and wenke lee , `` using an ensemble of one - class svm classifiers to harden payload - based anomaly detection systems , '' in _ sixth international conference on data mining . ieee icdm06 . _ , 2006 , pp . 488498 . david heckerman , david m. chickering , christopher meek , robert rounthwaite , and carl kadie , `` dependency networks for inference , collaborative filtering , and data visualization , '' , vol . 1 , pp . 4975 , 2001 . nelson h. yung and andrew h. lai , `` detection of vehicle occlusion using a generalized deformable model , '' in _ proceedings of the ieee international symposium on circuits and systems _ , 1998 , . 4 , pp .	, we propose i ) a novel algorithm to efficiently separate , i.e. , detect and localize , possible corruptions from a given suspicious data instance and ii ) a _ maximum a posteriori _ ( map ) estimator to impute the corrupted data . as a generalization to euclidean distance the proposed framework is tested over several well - known machine learning data sets with synthetically generated corruptions ; and experimentally shown to produce remarkable improvements in terms of classification purposes with strong corruption separation capabilities . our experiments also indicate that the proposed algorithms outperform the typical approaches and are robust to varying training phase conditions .	we introduce a comprehensive and statistical framework in a model free setting for a complete treatment of localized data corruptions due to severe noise sources , e.g. , an occluder in the case of a visual recording . within this framework , we propose i ) a novel algorithm to efficiently separate , i.e. , detect and localize , possible corruptions from a given suspicious data instance and ii ) a _ maximum a posteriori _ ( map ) estimator to impute the corrupted data . as a generalization to euclidean distance , we also propose a novel distance measure , which is based on the ranked deviations among the data attributes and empirically shown to be superior in separating the corruptions . our algorithm first splits the suspicious instance into parts through a binary partitioning tree in the space of data attributes and iteratively tests those parts to detect local anomalies using the nominal statistics extracted from an uncorrupted ( clean ) reference data set . once each part is labeled as anomalous vs normal , the corresponding binary patterns over this tree that characterize corruptions are identified and the affected attributes are imputed . under a certain conditional independency structure assumed for the binary patterns , we analytically show that the false alarm rate of the introduced algorithm in detecting the corruptions is independent of the data and can be directly set without any parameter tuning . the proposed framework is tested over several well - known machine learning data sets with synthetically generated corruptions ; and experimentally shown to produce remarkable improvements in terms of classification purposes with strong corruption separation capabilities . our experiments also indicate that the proposed algorithms outperform the typical approaches and are robust to varying training phase conditions . localized corruption , occlusion , map based imputation , anomaly detection .
cond-mat0001235	i	the microscopic understanding of the effect of charge carrier doping on spin@xmath0 antiferromagnetic ( afm ) mott insulators is the central issue of the high - temperature superconducting cuprates . @xcite many puzzling experimental features of these systems @xcite suggest that a fundamental law of nature remains to be recognized . extremely low doping ( @xmath1 charge carriers per site ) leads to a complete destruction of the long - range afm order , and a transition to an unusual non - fermi - liquid metal . this unusual metal becomes superconducting , with the transition temperature @xmath2 strongly dependent on the doping @xmath3 . the maximum @xmath2 is reached for dopings around @xmath4 . for higher dopings the critical temperature decreases to zero , and in the overdoped region a crossover towards a ( non - superconducting ) fermi - liquid takes place . two central questions require resolution . the first one concerns the nature of the charge carriers responsible for this non - fermi - liquid metallic behavior . this is a fundamental issue , since it lies outside the framework of landau s fermi - liquid theory and it necessitates understanding the appearance of non - quasiparticle - like charge carriers in a system of interacting electrons . the second question concerns the nature of strong attractive pairing between these charge carriers , given the purely repulsive interaction between the constituent electrons . in conventional superconductors , the pairing attraction is due to overscreening of the electron - electron coulomb repulsion by the ionic lattice . in the case of the high - temperature superconducting cuprates , it has been suggested @xcite that pairing is an intrinsic property of the electron gas itself mediated by afm spin - fluctuations of the doped system . accordingly , the challenge is to identify a strong attractive force based purely on repulsive coulomb interactions . in this paper , we derive such a force and demonstrate that it leads to d - wave pairing of charge carrying holes introduced by doping a quantum , spin-@xmath5 , mott - hubbard antiferromagnet . the simplest model hamiltonians used to investigate the cuprate physics are the hubbard model and the closely related t - j model . unlike the 1d problem , an exact solution for the 2d hubbard hamiltonian is not known . as a result , various approximations are necessary . although the application of the mean - field theory has been severely criticized in this context , it provides a valuable reference point for incorporating fluctuation effects . moreover , even for the 1d hubbard model , essential features of the exact solution may be recaptured by judiciously incorporating fluctuation and tunneling effects into mean - field theory . @xcite the most straightforward mean - field theory is the hartree - fock approximation ( hfa ) . at half - filling ( @xmath6 ) the hfa predicts an afm mott insulator ground - state . as the system is doped , hfa suggests that charge carrier holes in the afm background assemble in charged stripes , which are quasi - one - dimensional structures . @xcite a large effort has been devoted to studying these charged stripes and relating them to certain features of the cuprates . @xcite recently , a more fundamental investigation of the many - electron problem has suggested the possibility of an alternative model hamiltonian for the cuprate physics . this model hamiltonian , called the spin - flux model , @xcite suggests that the long - range coulomb interaction between spin-@xmath5 electrons leads to qualitative new physics , not apparent in the conventional hubbard model ( see section 2 ) . the results of the hartree - fock study @xcite of this spin - flux model are summarized in section 3 . they suggests that the undoped parent compound is also an afm mott insulator . however , unlike the conventional hubbard model , the one - electron dispersion relations of the afm mean - field in the spin - flux model match those measured experimentally through angle - resolved photo - emission for undoped cuprates . a proper description of the highest occupied electronic states ( as provided by the spin - flux model ) , is crucial to considerations of doping . the spin - flux model and the conventional hubbard model differ dramatically in this regard . at the hf level , the doping holes added to the afm background of the spin - flux model are trapped in the core of antiferromagnetic spin vortices . this composite object ( meron - vortex ) is a bosonic charged collective mode of the many - electron system ( the total spin of the magnetic vortex is zero ) . the reversal of the spin - charge connection provides a microscopic basis for non - fermi - liquid behavior . a magnetic vortex is strongly attracted to an antivortex . this attraction increases logarithmically with the distance between the vortex cores , and is stronger than the unscreened coulomb repulsion between the charge meron - vortex cores . in effect , the increase in coulomb energy between a given pair of holes is more than offset by the lowering in exchange energy between the background electrons as their vortices approach each other from far away . as the inter - vortex distance increases , more and more spins are rotated out of their afm background orientation and the total energy of the system increases . thus , even at the hf level , the spin - flux model provides a fundamental underpinning for the origin of both non - fermi - liquid behavior , and strong pairing between the charge carriers . while providing a good starting point , the hartree - fock approximation also has serious shortcomings . for instance , the ground - state wavefunction in the presence of doping is non - homogeneous ( the static meron - vortices of the spin - flux model , or the charged stripes of the conventional hubbard model , break translational symmetry ) . physically , one expects that these charge carriers can move along the planes , resulting in a wavefunction which preserves the translational symmetry of the original hamiltonian . quantum dynamics of the charge carriers also determines whether the doped ground - state is really a metal . charge carriers in the optimally doped cuprates are quite mobile excitations , although their scattering rates are radically different from electrons in a conventional fermi liquid . a consistent way of treating the quantum dynamics of the charge carriers is provided by the configuration interaction ( ci ) method,@xcite described in section 4 . here , a linear combination of hf wavefunctions is used in order to restore the various broken symmetries . for instance , in a doped system the ci wavefunction is chosen to be a linear combination of hf wavefunctions with the charge carrier localized at different sites . certain types of charge carriers can lower their total energy substantially by quantum mechanically hopping from one site to the next . we tested the accuracy of the ci method against the exact solution @xcite of the one - dimensional hubbard model in reference 3 . in the 1d hubbard model the ci method describes the quantum dynamics of charged domain wall solitons in the afm background . by including these effects as fluctuation corrections to the hartree - fock mean - field theory , the ci method provides excellent agreement with the exact bethe ansatz solution for the ground - state energy of the doped 1d hubbard chain , over the entire @xmath7 range . the ci method also leads to a clear demonstration of the spin - charge separation in 1d . addition of one doping hole to the half - filled antiferromagnetic chain results in the appearance of two different carriers : a charged bosonic domain - wall ( which carries the charge but no spin ) and a neutral spin-1/2 domain wall ( which carries the spin but no charge ) . this study @xcite demonstrates the effectiveness of the ci method . in this paper we use the ci method to investigate dynamics of the charged meron - vortices in the spin - flux model . throughout this paper we exploit and refer to the analogy between the charge excitations of the 1d hubbard model and the 2d spin - flux model , @xcite apparent in the ci approach . @xcite the ci results for the spin - flux model ( presented in section 4 ) confirm that the meron - vortices are very mobile , suggesting that a collection of such mobile bosonic charge carriers is a non - fermi - liquid metal . the ci method also allows us to identify the rotational symmetry of the meron - antimeron pair wavefunction to be d - wave for the most stable pairs . an energetically more expensive metastable s - wave pairing is also possible . the possibility of spin - charge separation in 2d is elucidated . a summary of the results , their interpretation and conclusions is provided in section 5 .	the magnetic exchange energy of the distorted afm background leads to a logarithmic vortex - antivortex attraction which overcomes the direct coulomb repulsion between holes localized on the vortex cores . the ci method systematically describes fluctuation and quantum tunneling corrections to the hartree - fock approximation ( hfa ) .	we investigate a microscopic model for strongly correlated electrons with both on - site and nearest neighbor coulomb repulsion on a 2d square lattice . this exhibits a state in which electrons undergo a `` somersault '' in their internal spin - space ( spin - flux ) as they traverse a closed loop in external coordinate space . when this spin-1/2 antiferromagnetic ( afm ) insulator is doped , the ground state is a liquid of charged , bosonic meron - vortices , which for topological reasons are created in vortex - antivortex pairs . the magnetic exchange energy of the distorted afm background leads to a logarithmic vortex - antivortex attraction which overcomes the direct coulomb repulsion between holes localized on the vortex cores . this leads to the appearance of pre - formed charged pairs . we use the configuration interaction ( ci ) method to study the quantum translational and rotational motion of various charged magnetic solitons and soliton pairs . the ci method systematically describes fluctuation and quantum tunneling corrections to the hartree - fock approximation ( hfa ) . we find that the lowest energy charged meron - antimeron pairs exhibit d - wave rotational symmetry , consistent with the symmetry of the cuprate superconducting order parameter . for a single hole in the 2d afm plane , we find a precursor to spin - charge separation in which a conventional charged spin - polaron dissociates into a singly charged meron - antimeron pair . this model provides a unified microscopic basis for ( i ) non - fermi - liquid transport properties , ( ii ) d - wave preformed charged carrier pairs , ( iii ) mid - infrared optical absorption , ( iv ) destruction of afm long range order with doping and other magnetic properties , and ( v ) certain aspects of angled resolved photo - emission spectroscopy ( arpes ) .
cond-mat0001235	r	the configuration interaction method utilizes a linear combination of judiciously chosen hartree - fock wavefunctions.@xcite in this section , we provide a short review of the relevant hartree - fock results for the spin - flux model . a full comparison between the hfa for the spin - flux model and the conventional hubbard model has been published elsewhere . @xcite one of the most widely used approximations for the many - electron problem is the static hartree - fock approximation ( hfa ) . in this approximation the many - body problem is reduced to one - electron problems in which each electron moves in a self - consistent manner depending on the mean - field potential of the other electrons in the system . while this method is insufficient , by itself , to capture all of the physics of low dimensional electronic systems with strong correlations , it provides a valuable starting point from which essential fluctuation corrections can be included . in particular , we use the hartree - fock method to establish the electronic structure and the static energies of various magnetic soliton structures . in the more general configuration interaction ( ci ) variational wavefunction , the solitons acquire quantum dynamics and describe large amplitude tunneling and fluctuation effects that go beyond mean field theory . in the hf approximation , the many - body wavefunction @xmath58 is decomposed into a slater determinant of effective one - electron orbitals . the one - electron orbitals are found from the condition that the total energy of the system is minimized @xmath59 in order to approximate the ground state of the spin - flux hamiltonian ( [ 1.104 ] ) , we consider a slater determinant trial - wavefunction of the form @xmath60 is the vacuum state , @xmath61 is the total number of electrons in the system and the one - electron states are given by @xmath62 here , the one - particle wave - functions @xmath63 form a complete and orthonormal system . using the wavefunction ( [ 2.3 ] ) in equation ( [ 2.1 ] ) , and minimizing with respect to the one - particle wavefunctions @xmath63 , we obtain the hartree - fock eigen - equations : where @xmath64 are the pauli spin matrices and the charge density , @xmath65 and the spin density , @xmath66 must be computed self - consistently . the notation @xmath67 appearing in ( [ 2.5 ] ) means that the sum is performed over the sites @xmath15 which are nearest - neighbors of the site @xmath12 . the self - consistent hartree - fock equations ( [ 2.5],[2.6],[2.7 ] ) must be satisfied by the occupied orbitals @xmath68 , but can also be used to compute the empty ( hole ) orbitals . the ground - state energy of the system in the hfa is given by @xmath69 where the single particle energies are obtained from ( [ 2.5 ] ) . the approximation scheme described above is called the unrestricted hartree - fock approximation , because we did not impose constraints on the wavefunction @xmath58 which would require it to be an eigenfunction of various symmetry operations which commute with the hamiltonian ( [ 1.104 ] ) . if these symmetries are enforced , the method is called the restricted hartree - fock approximation . we use the unrestricted hfa since it leads to lower energies . the breaking of symmetries in our case implies that electronic correlations are more effectively taken into account . @xcite the restoration of these symmetries is deferred until the ci wavefunction is introduced . in the undoped ( half - filled ) case , the self - consistent hartree - fock equations can be solved analytically for the infinite system , using plane - wave one - particle wave - functions . in the unrestricted hartree - fock approach , doping the system leads to the appearance of inhomogeneous solutions , which break the translational invariance . in this case , we solve the unrestricted self - consistent hartree - fock equations numerically on a finite lattice . starting with an initial spin and charge distribution @xmath70 and @xmath71 , we numerically solve the eigenproblem ( [ 2.5 ] ) and find the hf eigenenergies @xmath72 and wavefunctions @xmath73 . these are used in eqs . ( [ 2.6 ] ) and ( [ 2.7 ] ) to calculate the new spin and charge distribution , and the procedure is repeated until self - consistency is reached . numerically , we define self - consistency by the condition that the largest variation of any of the charge or spin components on any of the sites of the lattice is less that @xmath74 between successive iterations . for the undoped system , the hartree - fock equations ( [ 2.5 ] ) for an infinite system are easily solved . in the cuprates , long - range afm order is experimentally observed . accordingly , we choose a spin distribution at the site @xmath75 of the form @xmath76 , where @xmath77 is the unit vector of some arbitrary direction , while the charge distribution is @xmath78 . in the spin - flux phase , it is convenient to choose a square unit cell , in order to simplify the description of the @xmath48 phase - factors . we make the simplest gauge choice compatible with the spin - flux condition for the @xmath79-matrices , namely that @xmath80 ( see fig . ( [ fig1.55 ] ) ) . this leads to the reduced square brillouin zone @xmath81 . from the hartree - fock equations we find two electronic bands , characterized by the dispersion relations : @xmath82 where each level is four - fold degenerate and @xmath83 are the noninteracting electron dispersion relations in the presence of spin - flux . the hf ground - state energy of the spin - flux afm background is given by ( see eq . ( [ 2.8 ] ) ) : @xmath84 where the afm local moment amplitude is determined by the self - consistency condition ( [ 2.7 ] ) @xmath85 at half - filling the valence band ( @xmath86 ) is completely filled , the conduction band ( @xmath87 ) is completely empty , and a mott - hubbard gap of magnitude @xmath88 opens between the valence and the conduction bands . the ground - state of the undoped spin - flux model is an afm mott insulator . it is interesting to note that the quasi - particle dispersion relation obtained in the presence of the spin - flux ( eq . ( [ 2.27 ] ) ) closely resembles the dispersion as measured through angle - resolved photo - emission spectroscopy ( arpes ) in a compound such as sr@xmath9cuo@xmath9cl@xmath9 @xcite ( see fig . [ fig2.13 ] ) . there is a a large peak centered at @xmath89 with an isotropic dispersion relation around it , observed on both the @xmath90 to @xmath91 and @xmath92 to @xmath93 lines . the spin - flux model in hfa exhibits another smaller peak at @xmath94 which is not resolvable in existing experimental data . this minor discrepancy may be due to next nearest neighbor hopping or other aspects of the electron - electron interaction which we have not yet been included in our model . @xcite the quasi - particle dispersion relation of the conventional hubbard model ( @xmath95 ) has a large peak at @xmath96 on the @xmath90 to @xmath91 line ( see fig . [ fig2.13 ] ) , but it is perfectly flat on the @xmath92 to @xmath93 line ( which is part of the large nested fermi surface of the conventional 2d hubbard model ) . also , it has a large crossing from the upper to the lower band - edge on the @xmath90 to @xmath92 line . this dispersion relation is very similar to that of the @xmath97 model ( see ref . 17 ) . while both the conventional and spin - flux model predict afm insulators at half - filling ( at least at the hf level ) , the spin - flux also provides a much better agreement with the dispersion relations , as measured by arpes . as in the 1d case , @xcite the effect of doping is the appearance of discrete levels deep inside the mott - hubbard gap . these levels are drawn into the gap from the top ( bottom ) of the undoped valence ( conduction ) bands . accordingly , the type of excitations created by doping depends strongly on topology of the electronic structure near the band edges . if we introduce just one hole in the plane , the self - consistent hfa solution is a conventional spin - polaron or `` spin - bag '' ( see fig . this type of excitation is the 2d analog of the 1d spin - polaron . @xcite the doping hole is localized around a particular site , leading to the appearance of a small ferromagnetic core around that site . the spin and charge distribution at the other sites are only slightly affected . in fact , the localization length of the charge depends on @xmath7 , and becomes very large as @xmath98 , since in this limit the mott - hubbard gap closes . for intermediate and large @xmath7 , the doping hole is almost completely localized on the five sites of the ferromagnetic core . the spin - bag is a charged fermion , as can be seen by direct inspection of its charge and spin distributions . this is also confirmed by its electronic structure ( see fig.3b ) . thus , the 2d spin - bag is indeed the analog of the 1d spin - polaron . @xcite the 2d analog of the 1d charged domain wall is the meron - vortex ( see fig . [ fig2.22 ] ) . like the 1d domain - wall , the meron - vortex is also a topological excitation , characterized by a topological ( winding ) number @xmath99 ( the spins on each sublattice rotate by @xmath100 on any closed contour surrounding the center of the meron ) . as such , a single meron - vortex can not be created in an extended afm background with cyclic boundary conditions by the introduction of a single hole ( just as a single isolated charged domain wall can not be created on an afm ( even ) chain with cyclic boundary conditions , by the introduction of a single hole ) . from a topological point of view , this is so because the afm background has a winding number 0 , and the winding number must be conserved , unless topological excitations migrate over the boundary into the considered region . however , excitations can be created in pairs of total topological number 0 . in the 1d case , this means creation of pairs of domain walls , while in 2d this means the creation of vortex - antivortex pairs . from figs . 4(a ) and 4(b ) we can see that the meron - vortex is a charged boson . the total spin of such a configuration is zero , while it carries the doping charge trapped in the vortex core . moreover , from its electronic spectrum ( fig . 4b ) we can see that only the extended states of the valence band are occupied . they are the only ones contributing to the total spin . since only one state is drawn from the valence band into the gap , to become a discrete bound level , it appears that an odd ( unpaired ) number of states remains in the valence band . however , one must remember that for topological reasons , merons must appear in vortex - antivortex pairs . therefore , the valence band has an even number of ( paired ) levels , and the total spin is zero . this argument for the bosonic character of the meron - vortex is identical to that for the charged domain wall in polyacetylene . @xcite unlike in the 1d case,@xcite we can not directly compare the excitation energy of the spin - bag with the excitation energy of the meron - vortex . the reason is that the excitation energy of the latter increases logarithmically with the size of the sample , and therefore an isolated meron - vortex is always energetically more expensive than a spin - bag . however , topology requires that merons and antimerons are created in pairs . the excitation energy of such a meron - antimeron pair is finite , allowing a meaningful comparison between excitation energies of a pair of spin - bags and a meron - antimeron pair . in figs . 5(a ) and 5(b ) we show the self - consistent spin and charge distributions for the lowest energy self - consistent hf configuration found when we add 2 holes to the afm background , in the spin - flux model , for @xmath101 . this configuration consists of a meron and an antimeron centered on second nearest - neighbor sites . as a result of interactions , the cores of the vortices are somewhat distorted . if the vortices were uncharged , vortex - antivortex pair annihilation would be possible . however , for charged vortices , the fermionic nature of the underlying electrons prevents two holes from being localized at the same site , in spite of the bosonic character of the collective excitation . a very interesting feature of this configuration is the strong topological attraction between the vortex and the antivortex . the closer the two cores are to each other , the smaller is the region in which the spins are rotated out of their background afm orientation by the vortices , and therefore the smaller is the excitation energy of the pair . since the holes are localized in the cores of the vortices , this topological attraction between vortices is an effective attraction between holes in the purely repulsive 2d electron system . this effect is unique to the spin - flux phase . in the conventional hubbard model , vortices are not stable excitations . the vortex - antivortex attraction increases as the logarithm of the distance between the cores . therefore , the pair of vortices should remain bound even if full unscreened @xmath102 coulomb repulsion exists between the charged cores , providing a compelling scenario for the existence of strongly bound pre - formed pairs in the underdoped regime . there is another possible self - consistent state for the system with two holes , consisting of two spin - bags far from each other ( such that their localized wave functions do not overlap ) . the excitation energy of such a pair of spin - bags is simply twice the excitation energy of a single spin - bag . when this excitation energy is compared to the excitation energy of the tightly bound meron - antimeron pair , we find that it is higher by @xmath103 ( for @xmath101 ) . in fact , for @xmath104 the hfa predicts that the meron - antimeron pair is the low - energy charged excitation , while for @xmath105 , the spin - bag is the low - energy charge carrier . this is analogous with the situation in 1d , where the spin - bag was predicted to be the low energy excitation for @xmath106 , in the hfa . @xcite as in 1d , however , we expect that this conclusion will be drastically modified once the charged solitons are allowed to move along the planes and the lowering of kinetic energy through translations is also taken into consideration . we complete this review of the hf results by pointing out that the strong analogy between the 1d hubbard model and the 2d spin - flux model is due to the similarity between the electronic structures at zero doping . as seen from fig.[fig2.13 ] , the 2d spin - flux model has isotropic dispersion relations about the @xmath96 point . this acts as a fermi point for the noninteracting system as it does in the 1d system . the two empty discrete levels drawn deep inside the mott - hubbard gap in the presence of the meron - vortex split from the @xmath96 peaks of the electron dispersion relation . the different topology of the large nested fermi surface of the conventional hubbard model leads to instability of the meron - antimeron pair . in fact , in the conventional hubbard model doping holes assemble in charged stripes , as opposed to the liquid of meron - antimeron pairs which is the low - energy state of the doped spin - flux model .	we use the configuration interaction ( ci ) method to study the quantum translational and rotational motion of various charged magnetic solitons and soliton pairs . we find that the lowest energy charged meron - antimeron pairs exhibit d - wave rotational symmetry , consistent with the symmetry of the cuprate superconducting order parameter . for a single hole in the 2d afm plane , we find a precursor to spin - charge separation in which a conventional charged spin - polaron dissociates into a singly charged meron - antimeron pair .	we investigate a microscopic model for strongly correlated electrons with both on - site and nearest neighbor coulomb repulsion on a 2d square lattice . this exhibits a state in which electrons undergo a `` somersault '' in their internal spin - space ( spin - flux ) as they traverse a closed loop in external coordinate space . when this spin-1/2 antiferromagnetic ( afm ) insulator is doped , the ground state is a liquid of charged , bosonic meron - vortices , which for topological reasons are created in vortex - antivortex pairs . the magnetic exchange energy of the distorted afm background leads to a logarithmic vortex - antivortex attraction which overcomes the direct coulomb repulsion between holes localized on the vortex cores . this leads to the appearance of pre - formed charged pairs . we use the configuration interaction ( ci ) method to study the quantum translational and rotational motion of various charged magnetic solitons and soliton pairs . the ci method systematically describes fluctuation and quantum tunneling corrections to the hartree - fock approximation ( hfa ) . we find that the lowest energy charged meron - antimeron pairs exhibit d - wave rotational symmetry , consistent with the symmetry of the cuprate superconducting order parameter . for a single hole in the 2d afm plane , we find a precursor to spin - charge separation in which a conventional charged spin - polaron dissociates into a singly charged meron - antimeron pair . this model provides a unified microscopic basis for ( i ) non - fermi - liquid transport properties , ( ii ) d - wave preformed charged carrier pairs , ( iii ) mid - infrared optical absorption , ( iv ) destruction of afm long range order with doping and other magnetic properties , and ( v ) certain aspects of angled resolved photo - emission spectroscopy ( arpes ) .
cond-mat0001235	m	the essence of the configuration interaction ( ci ) method is that the ground - state wavefunction , for a system with @xmath61 electrons , is not represented by just a single @xmath107 slater determinant ( as in the hfa ) , but a judiciously chosen linear combination of such slater determinants . @xcite given the fact that the set of all possible slater determinants ( with all possible occupation numbers ) generated from a complete set of one - electron orbitals constitute a complete basis of the @xmath61-particle hilbert space , our aim is to pick out a subset of slater determinants which captures the essential physics of the exact solution . consider the ci ground - state wavefunction given by @xmath108 is a distinct @xmath107 slater determinant and the coefficients @xmath109 are chosen to satisfy the minimization principle : @xmath110 this leads to the system of ci equations @xmath111 where @xmath112 is the energy of the system in the @xmath113 state , @xmath114 are the matrix elements of the hamiltonian in the basis of slater determinants @xmath115 , and @xmath116 are the overlap matrix elements of the slater determinants ( which are not necessarily orthogonal ) . the ci solution is easily found by solving the linear system of equations ( [ 3.3 ] ) , once the basis of slater determinants @xmath117 is chosen . if we denote by @xmath118 the @xmath119 one - electron occupied orbitals of the slater determinant @xmath120 , these matrix elements are given by : @xmath121{ccc } \beta_{1,1}^{nm } & ... & \beta_{1,n_e}^{nm } \\ \vdots & & \vdots\\ \beta_{n_e,1}^{nm } & ... & \beta_{n_e , n_e}^{nm } \\ \end{array } \right\|\ ] ] the matrix elements of the hamiltonian ( [ 1.104 ] ) can be written as : @xmath122 where the expectation values of the hopping and on - site interaction terms are : @xmath123{ccccc } \beta_{1,1}^{nm}& ... &t_{1,p}^{nm}& ... &\beta_{1,n_e}^{nm}\\ \vdots & & \vdots & & \vdots\\ \beta_{n_e,1}^{nm}& ... &t_{n_e , p}^{nm}& ... &\beta_{n_e , n_e}^{nm } \\ \end{array } \right\|\ ] ] and @xmath124{ccccccc } \beta_{1,1}^{nm } \!\!& ... \!\!&u_{1,p_1}^{nm}(i)\!\ ! \!\!&d_{1,p_2}^{nm}(i)\!\!& ... \!\ ! & \beta_{1,n_e}^{nm } \\ \vdots & & \vdots & & \vdots & & \vdots\\ \beta_{n_e,1}^{nm}\!\!& ... \!\!&u_{n_e , p_1}^{nm}(i)\!\ ! & ... \!\!&d_{n_e , p_2}^{nm}(i)\!\!& ... \!\ ! & \beta_{n_e , n_e}^{nm}\\ \end{array } \right\|_{.}\ ] ] here , @xmath125 @xmath126 @xmath127 and @xmath128 we now consider the specific choice of the slater determinant basis @xmath115 . strictly speaking , one may choose an optimized basis of slater determinants from the general variational principle : @xmath129 however , implementation of this full trial - function minimization scheme ( also known as a multi - reference self - consistent mean - field approach @xcite ) is numerically cumbersome even for medium - sized systems . instead , we select the slater determinant basis @xmath115 from the set of broken symmetry , unrestricted hartree - fock wavefunctions ( [ 2.3 ] ) , their symmetry related partners and their excitations . clearly , ( [ 2.3 ] ) satisfies ( [ 3.4 ] ) by itself , provided that the @xmath130 coefficients corresponding to the other slater determinants in eq.([3.1 ] ) are set to zero ( see eq . ( [ 2.1 ] ) ) . since this unrestricted hf wavefunction is not translationally invariant ( the doping hole is always localized somewhere on the lattice ) , we can restore the translational invariance of the ci ground - state wavefunction by also including in the basis of slater determinants all the possible lattice translations of this unrestricted hf wavefunction . furthermore , if the self - consistent configuration is not rotationally - invariant ( e.g. a meron - antimeron pair ) , all possible rotations must be performed as well . by rotation we mean changing the relative position of the meron and antimeron while keeping their center of mass fixed . clearly , all the translated hf slater determinants lead to the same hf ground - state energy @xmath131 as defined by eq . ( [ 2.8 ] ) . the ci method lifts the degeneracy between states with the hole - induced configuration localized at different sites ( see eq . ( [ 3.3 ] ) ) , thereby restoring translational invariance . we may identify the lowering in the total energy due to the lifting of this degeneracy as quantum mechanical kinetic energy of deconfinement which the doping - induced configuration saves through hopping along the lattice . in addition , quantum fluctuations in the internal structure of a magnetic soliton can be incorporated by including the lowest order excited state configurations of the static hartree - fock energy spectrum . such wavefunctions are given by @xmath132 , where @xmath133 labels an excited particle state and @xmath134 labels the hole which is left behind ( see eq . ( [ 2.3 ] ) ) . once again , all possible translations ( and non - trivial rotations ) of this `` excited '' configurations must be included in the full ci wavefunction . these additions can describe changes in the `` shape '' of the soliton as it undergoes quantum mechanical motion along the plane . the ci method is described in more detail in reference 3 , where it is used to study the 1d hubbard chain in order to gauge its accuracy by comparing its results with the exact bethe ansatz solution . we showed that the ci method recaptures the essential physical features of the exact solution of the 1d hubbard chain , such as spin - charge separation , as well as leading to remarkable agreement of ground state energies of doped chains for all values of @xmath7 . the main difference between the 1d case and the 2d case is the computation time required . the computation time for one matrix element @xmath135 scales roughly like @xmath136 , where @xmath137 is the number of sites . the number of configurations included in the ci set scales as @xmath138 when @xmath139 solitons are present . for both an @xmath137-site chain and an @xmath140 lattice , the hf `` bulk '' limit is reached for @xmath141 . in the 1d case @xcite we used chains with @xmath142 , and numerical calculations can be easily performed . however , in 2d the smallest acceptable system has 100 sites , leading to an enormous increase in the computation time . nevertheless , our sample of results in 2d suggest a simple and clear physical picture which we describe below . the charged spin - bag carries a spin of 1/2 . let @xmath143 be the hf determinants for the spin - bag centered at any two nearest neighbor sites , respectively , and let @xmath144 be the total spin operator in the @xmath145-direction . then , @xmath146 . since the hubbard hamiltonian commutes with @xmath147 , it follows that @xmath148 . from the ci equation ( [ 3.3 ] ) we conclude that there is no mixing between states with different total spin . as a result , it is enough to include in the ci set only those configurations with the spin bag localized on the same magnetic sublattice . let us denote by @xmath149 the initial static hartree - fock configuration , and by @xmath150 the configuration obtained through its translation by @xmath151 sites in the x - direction and @xmath152 sites in the y - direction ( cyclic boundary conditions are imposed ) . the condition that only configurations on the same sublattice are included means that @xmath153 must be an even number , and the cyclic boundary conditions mean that @xmath154 , for a @xmath155 lattice . as explained in detail in the 1d analysis , @xcite mixing configurations with the charged spin - bag localized at different sites and then subtracting out the contribution of the undoped afm background allows us to calculate the dispersion band of the spin - bag itself : @xmath156 here , the total energy of the lattice with the spin - bag @xmath157 and the ci wave - function @xmath158 ) . the finite size of the lattice and cyclic boundary conditions restricts the calculation to @xmath159-points of the form @xmath160 , where @xmath161 is any pair of integer numbers . as usual , only @xmath159-points inside the first brillouin zone need to be considered . an analysis of the dependence of the spin - bag dispersion relation @xmath162 on the size @xmath140 of the lattice is shown in fig . [ fig3.20 ] , for the conventional hubbard model ( upper panel ) and spin - flux model ( lower panel ) , and @xmath101 . we used 6x6 , 8x8 , 10x10 and ( only for the spin - flux model ) 12x12 lattices . the dispersion relation is plotted along lines of high symmetry of the full brillouin zone . for comparison , we also show the excitation energy @xmath163 obtained in the static hfa as a full line . for both models , we see that the spin - bag dispersion band is almost converged , even though we used quite small lattices . the convergence is somewhat slower in the spin - flux case , as seen most clearly at the ( 0,0 ) point . although the values obtained from the four lattices all differ at ( 0,0 ) , the extremum values correspond to the 6x6 and the 8x8 lattices , while the values for the 10x10 and 12x12 lattices are indistinguishable . we conclude that the fit ( [ 3.40 ] ) is legitimate . from fig . [ fig3.20 ] we also see that the dispersion relations for the spin - bag in the two different models are very different . the dispersion relations over the full 2d brillouin zone are shown in fig . [ fig3.21 ] , and they are seen to mimic the electronic dispersion relation of the underlying undoped afm background , shown in fig . [ fig2.13 ] . this is consistent with the quasi - particle nature of this charged spin-1/2 spin - bag . in the conventional hubbard model , the undoped afm background has a large nested fermi surface along the @xmath92 to @xmath93 line , and it is exactly along this line that the spin - bag dispersion band has a minimum . similarly , the lowest energy of the spin - bag of the spin - flux model is at @xmath89 , corresponding to the fermi points of the underlying undoped spin - flux afm background . the extra kinetic energy @xmath164 saved by the spin - bag through quantum hopping is @xmath165 in the conventional model and @xmath166 in the spin - flux model ( for @xmath101 ) . since the spin - bag is confined to one magnetic sublattice , it must tunnel two lattice constants to the next allowed site . consequently , the energy gained through hopping ( of order @xmath167 ) is small . this is displayed , for the spin - bag of the spin - flux model , in fig . [ fig3.24 ] , where we plot the lowering in kinetic energy of the deconfined spin - bag @xmath168 as a function of @xmath169 . a similar dependence for the spin - bag of the conventional hubbard model is presented elsewhere . @xcite as in the 1d case , we conclude that the spin - bag in 2d is a rather immobile quasiparticle - like excitation . in the 1d model it is energetically favorable for the immobile spin - bag to decay into a charged bosonic domain wall and a neutral fermionic domain wall , resulting in spin - charge separation . @xcite the analog of the 1d charged bosonic domain wall is the 2d charged bosonic meron - vortex of the spin - flux model . if the spin - bag decays into a charged meron - vortex , a magnetic antivortex must also be created for topological reasons . unlike the pair of domain walls in the 1d case , the vortex - antivortex pair is tightly bound by a topological binding potential that increases as the logarithm of the vortex - antivortex separation . therefore , we expect that the doping charge is shared between the two magnetic vortices . one technical problem for testing this hypothesis is that such a configuration ( a vortex - antivortex pair sharing one doping hole ) is not self - consistent at the static hartree - fock level . in the static approximation we require two doping holes to stabilize two vortex cores and create a meron - antimeron pair . we can , however , construct a trial wavefunction to describe the singly - charged vortex - antivortex pair , by adding one electron in the first empty state of the self - consistent doubly - charged meron - antimeron configuration . the first empty levels of the meron - antimeron pair are the localized levels bound in the vortex cores , two for each vortex ( see fig . because of degeneracy between the two lower discrete levels of the pair , we have in fact two distinct trial wave - functions , obtained by adding one electron in either of these two lower localized gap electronic states of a self - consistent meron - antimeron pair . these wavefunctions are not invariant to rotations ( see fig . [ fig2.25 ] ) . therefore we must include in the ci set of slater determinants the configurations obtained through @xmath170 rotations of the vortex - antivortex pair about its fixed center of mass in addition to translated configurations . as a result , we have a total of @xmath171 configurations describing the singly charged vortex - antivortex pair localized at all possible sites with all possible orientations about the center of mass . we performed this ci analysis for a @xmath172 lattice and @xmath101 . the hf energy of a simple static spin - bag is @xmath173 ( measured with respect to the hf energy of the undoped afm background , equal to @xmath174 ) . the energy of the static singly - charged vortex - antivortex pair is @xmath175 . thus , we see that because this singly - charged pair trial wavefunction is not self - consistent , in the static case this configuration is energetically much more costly than the self - consistent spin - bag configuration . however , if we allow for quantum motion of these configurations , the situation changes dramatically . performing the ci analysis for the set of all possible translated spin - bag configurations , we find that the energy of the spin - bag is lowered to @xmath176 . performing the ci analysis for the set of all translated and rotated singly - charged vortex - antivortex pairs we find that this configuration s energy is lowered to @xmath177 . this shows that the vortex - antivortex pair has lowered its translational and rotational kinetic energy by almost @xmath178 , thereby becoming the low - energy charge carrier . this large number is not surprising , since unlike the spin - bag , the vortex - antivortex pair is not constrained to motion on one magnetic sublattice . as a result , such configurations lower their kinetic energy by an amount on the scale of @xmath24 , as opposed to @xmath167 for the spin - bag configuration . for larger @xmath7 values this effect is even more pronounced . we conclude that these results strongly support the hypothesis of spin - bag dissociation into a much more mobile singly - charged vortex - antivortex pair , analogous to the 1d spin - bag dissociation into a pair of a charged bosonic domain - wall and a neutral fermionic domain - wall . @xcite unlike in the 1d case , however , we do not have distinct charge and spin carriers for the composite excitation . instead the spin and the charge are shared equally between the vortex and the antivortex . if , on the other hand , there was a mechanism whereby the vortices became unbound , complete spin - charge separation could occur , in which one vortex traps the hole ( and is therefore a charged meron ) and the other vortex carries the spin , in a lotus - flower@xcite ( or undoped magnetic meron ) configurations . in the absence of the corresponding self - consistent static hf configuration we are not able to settle this question . at very low doping , the strong vortex - antivortex topological attraction binds the spin and charge together . this is different from the 1d case , where the absence of long - range interactions between the domain - walls allow for a complete spin - charge separation at any doping and even at zero temperature . this scenario opens a new avenue for research into how the system evolves with doping . if each hole is dressed into a singly - charged vortex - antivortex pair , when two such pairs overlap it is possible that both doping charges move to the same pair , creating a meron - antimeron pair of charged bosons . such pre - formed charge pairs may condense into a superconducting state at low temperatures . the other uncharged vortex - antivortex pair may either collapse and disappear ( this is likely to happen at low - temperatures ) or remain as a magnetic excitation of the system ( at higher temperatures ) , mediating the destruction of the long - range afm order , the renormalization of the spin - wave spectrum and the opening of the spin pseudogap . from the static hf analysis we found that the most stable static self - consistent configuration with two doping holes added to the afm background of the spin - flux model is the meron - antimeron pair , for @xmath179 . at larger @xmath7 , two charged spin - bags become more stable , in the static hf approximation . this is in close analogy to the prediction that the spin - bag is energetically more favorable than the static charged domain - wall for @xmath180 , in the hfa of the 1d hubbard model . @xcite however , in the 1d case the charged domain - wall is considerably more mobile than the charged spin bag , gaining a kinetic energy of the order of @xmath24 as opposed to @xmath167 energy gained by the spin - bag . as a result , when this kinetic energy of deconfinement is taken into account within the ci method , the charged domain - wall is found to be the relevant charged excitation for all values of @xmath7 . a similar picture emerges in the 2d case , because the meron - vortices are much more mobile than the spin - bags . for the 2d system , we have shown that the charged spin - bag has very similar behavior to the 1d charged spin - bag . the analog of the 1d charged bosonic domain - wall is the 2d charged bosonic meron - vortex . we now consider the properties of the doubly - charged meron - antimeron pair . all the numerical results quoted in the rest of this section refer to a meron - antimeron pair on a 10x10 lattice , in the spin - flux model with @xmath101 . as already discussed , the meron - antimeron pair is not rotationally invariant . we can find the rotational kinetic energy saved by the pair as it rotates about its center of mass . in the present case , only 4 configurations need to be included , corresponding to the four possible self - consistent arrangements of the meron and antimeron about their fixed center of mass ( see fig . [ fig3.28 ] ) . simple rotation by @xmath170 of the one - particle orbitals @xmath181 about the center of mass is not , however , sufficient to generate the rotated configurations . first of all , the @xmath170 rotation also changes the spin - flux parameterization . if the spin - flux of the initial configuration is @xmath57 , a @xmath170 rotation leads to a state corresponding to the rotated configuration @xmath182 . thus , following the @xmath170 rotation , a unitary transformation must be performed in order to restore the initial spin - flux parameterization . for the case cited above , this simply implies the change in the one - particle orbitals @xmath183 for all sites @xmath184 which are a type 2 site of the unit cell , in other words sites with even @xmath185 and odd @xmath186 ( also , see fig . [ fig1.55 ] ) . the second observation is that the rotation by @xmath170 also changes ( flips ) all the spins of the afm background surrounding the pair . thus , an extra @xmath187 rotation about an axis perpendicular to the lattice plane is necessary to restore the alignment of the afm background . following these transformations it is straightforward to generate the slater determinants @xmath188 and @xmath189 from the initial self - consistent hf meron - antimeron pair described by @xmath190 . the ci method can be used to find the rotational energy saved by superposing these rotated meron - antimeron configurations . the lowest ci energy found is @xmath191 below the energy of the static pair , and corresponds to d - wave symmetry . by this we mean that the coefficients @xmath109 multiplying the 4 rotated states in the ci wave - function @xmath192 . translation of a pair over the whole lattice can also be investigated . since the pair does not carry any spin , all possible translations must be included ( there is no restriction to same magnetic sublattice configurations ) . this leads to a total of @xmath193 possible configurations for a @xmath140 lattice . again , when various configurations are generated from the initial self - consistent hf meron - antimeron state @xmath194 , care must be taken to preserve the same spin - flux parameterization and the same afm background orientation . this can be achieved performing transformations similar to the ones described above . as a result of performing the ci method on the set of translated states , we find the dispersion relation of the ( un - rotated ) meron - antimeron pair . this is shown in fig . [ fig3.25 ] . in this plot we show the total energy of the lattice with the moving meron - antimeron pair , as a function of the total momentum of the pair . quantum hopping of the meron - antimeron pair lowers its total energy by an extra @xmath195 . two other interesting features are observed in fig . [ fig3.25 ] . the first one is that the dispersion relation of this rigidly polarized pair is not invariant to rotations by @xmath170 , as expected . more important is that the minima of the dispersion relation occur at the @xmath91 points . since the momentum of the pair is twice the momentum of either the meron or the antimeron , this is consistent with the fact that in their lowest energy state , both the meron and the antimeron have momenta of @xmath89 , in the spin - flux model . the doubling of the size of the brillouin zone is also a direct consequence of this doubling of total momentum ( for comparison with undoped dispersion relation , see fig . [ fig2.13 ] ) . however , to obtain the true energy of the charged pair , we must mix all @xmath196 rotated and translated meron - antimeron configurations . all have the same static hf energy and are equally important in the ci method . let @xmath197 denote the initial self - consistent static hartree - fock meron - antimeron configuration , and @xmath198 denote the configuration obtained through translation by @xmath151 sites in the x - direction and @xmath152 sites in the y - direction , as well as a rotation by an angle of @xmath199 of the pair about its center of mass . here @xmath200 and @xmath201 ( cyclic boundary conditions are imposed ) . the ci wavefunctions are then given by : @xmath202 the dispersion relation @xmath203 obtained from this complete set is shown in fig . [ fig3.26 ] . the reference point is the hf energy of the self - consistent meron - antimeron pair @xmath204 . thus , we see that the total kinetic energy saved by the freely moving and rotating meron - antimeron pair is @xmath205 , when the total momentum of the pair is @xmath91 . this energy equals the sum @xmath206 of rotational and translational kinetic energies found before ( the number of significant figures indicates the estimated accuracy of the computational method ) . the rotational invariance of the dispersion band is also restored . besides the absolute minima about the @xmath91 points , there is a more shallow minimum region about the @xmath90 point . the rotational symmetry of the meron - antimeron pair wavefunction , defined by the coefficients @xmath207 , is a function of the total momentum carried by the pair , as shown in fig . [ fig3.27 ] . the absolute minima points @xmath91 and the area around them correspond to pairs with d - wave symmetry . by this , we mean that the coefficients @xmath208 have the form @xmath209 with @xmath210 , i.e. @xmath211 . the core area , about the local minimum @xmath90 point , corresponds to s - wave symmetry . in this region the coefficients @xmath212 again satisfy eq . ( [ 3.101 ] ) , but for @xmath213 , i.e. @xmath214 . the intermediary area appears to be a mixture of different @xmath215 values . a simple decomposition of the form ( [ 3.101 ] ) is no longer possible . instead , a sum of such terms corresponding to different @xmath215 values is required . since we only have rotations by @xmath170 , a unique identification of the composite symmetry is not possible . moreover , the energy of the states in this intermediary area is at the top of the dispersion band . in order to find the correct ci states for energies well above the static hf value ( i.e. larger than zero , in this case ) we must add to the ci set the first set of excited hf states . for a meron - antimeron pair , excitation of an electron from the valence band onto the empty localized levels inside the mott - hubbard gap costs about 1.5 t of energy , for @xmath101 , so such states should contribute significantly in the ci states with positive energies and modify their dispersion and symmetry ( for this reason , we do not show the upper three high - energy bands in fig . [ fig3.26 ] ) . consequently , both the energy and the symmetry of the states in the intermediary area may be modified from the ones shown in fig . [ fig3.26 ] . however , the minima at @xmath91 and @xmath90 are at energies well below zero . their energies and rotational symmetry are unaffected by additions of higher energy configurations to the ci set . the fact that we obtain two distinct minima is not very surprising . as argued before , we expect that individual merons and antimerons are created with momenta of @xmath216 . as a result , two different couplings are possible . a @xmath217 ) meron can pair with a @xmath217 ) antimeron , creating a pair of total momentum @xmath91 . this is the most stable coupling , leading to the lowest possible energy of @xmath218 below the static hf energy . this pair has d - wave symmetry . the second possible coupling is between a @xmath217 ) meron and a @xmath219 ) antimeron . this pair has a total momentum of @xmath90 , and s - wave symmetry . however , this coupling is less strong . for the @xmath101 case considered , the energy of the s - wave @xmath90 pair is @xmath220 above the energy of the d - wave @xmath91 pair . the existence of both d - wave and s - wave pairing , and the dominance of the d - wave pairing , have been established experimentally for the high - t@xmath23 cuprates . @xcite we are not aware of any other microscopic theory that predicts the two types of pairing to appear in different regions of the brillouin zone . the total kinetic energy saved by the meron - antimeron pair through quantum hopping and rotation is of order @xmath24 , as expected , since the pair is not restricted to one magnetic sublattice and tunneling is not required for motion . consequently , we expect that the energy saved by the meron - antimeron pair for larger values of @xmath7 is comparably large . on the other hand , the energy saved by the spin bag through tunneling motion scales like @xmath167 . in fact , we argued that a spin - bag may dissociate into a singly - charged vortex - antivortex pair in order to enhance its mobility . however , even if dissociation does not occur , the kinetic energy saved by a pair of spin - bags is significantly smaller than the kinetic energy saved by the meron - antimeron pair . this shows that for @xmath101 the meron - antimeron pair is even more favorable energetically than the hfa predicts and suggests that the @xmath7 range where meron - antimeron pair formation occurs may extend well beyond the @xmath221 limit found within the hfa . @xcite in the 1d case , the range of stability of the charged domain wall versus the charged spin - bag is extended ( from the hf prediction of @xmath222 ) to all @xmath7 range.@xcite a numerical analysis is needed to determine if the limit is extended to infinity in the 2d case as well .	when this spin-1/2 antiferromagnetic ( afm ) insulator is doped , the ground state is a liquid of charged , bosonic meron - vortices , which for topological reasons are created in vortex - antivortex pairs . this model provides a unified microscopic basis for ( i ) non - fermi - liquid transport properties , ( ii ) d - wave preformed charged carrier pairs , ( iii ) mid - infrared optical absorption , ( iv ) destruction of afm long range order with doping and other magnetic properties , and ( v ) certain aspects of angled resolved photo - emission spectroscopy ( arpes ) .	we investigate a microscopic model for strongly correlated electrons with both on - site and nearest neighbor coulomb repulsion on a 2d square lattice . this exhibits a state in which electrons undergo a `` somersault '' in their internal spin - space ( spin - flux ) as they traverse a closed loop in external coordinate space . when this spin-1/2 antiferromagnetic ( afm ) insulator is doped , the ground state is a liquid of charged , bosonic meron - vortices , which for topological reasons are created in vortex - antivortex pairs . the magnetic exchange energy of the distorted afm background leads to a logarithmic vortex - antivortex attraction which overcomes the direct coulomb repulsion between holes localized on the vortex cores . this leads to the appearance of pre - formed charged pairs . we use the configuration interaction ( ci ) method to study the quantum translational and rotational motion of various charged magnetic solitons and soliton pairs . the ci method systematically describes fluctuation and quantum tunneling corrections to the hartree - fock approximation ( hfa ) . we find that the lowest energy charged meron - antimeron pairs exhibit d - wave rotational symmetry , consistent with the symmetry of the cuprate superconducting order parameter . for a single hole in the 2d afm plane , we find a precursor to spin - charge separation in which a conventional charged spin - polaron dissociates into a singly charged meron - antimeron pair . this model provides a unified microscopic basis for ( i ) non - fermi - liquid transport properties , ( ii ) d - wave preformed charged carrier pairs , ( iii ) mid - infrared optical absorption , ( iv ) destruction of afm long range order with doping and other magnetic properties , and ( v ) certain aspects of angled resolved photo - emission spectroscopy ( arpes ) .
1108.2281	i	in this paper we begin the systematic study of legendrian graphs in @xmath6 with the standard contact structure . these are embedded graphs that are everywhere tangent to the contact planes . legendrian graphs have appeared naturally in several important contexts in the study of contact manifolds . they are used in giroux s proof of existence of open book decompositions compatible with a given contact structure , see @xcite . legendrian graphs also appear in the proof of eliashberg s and fraser s result which says that in a tight contact structure the unknot is determined up to legendrian isotopy by the invariants @xmath7 and @xmath8 , see @xcite . yet no study of legendrian graphs , until now , has been undertaken . we remedy this by establishing the foundations for what we expect will be a very rich field . a _ spatial graph _ is an embedding of a graph into @xmath9 an _ abstract graph _ is a set of vertices together with a set of edges between them , without any specified embedding . we will throughout this paper refer to an abstract graph as simply a graph . in section [ graphs ] , we show there is no obstruction to having a legendrian realization of any spatial graph . we extend the classical invariants thurston - bennequin number , @xmath7 , and rotation number , @xmath8 , from legendrian knots to legendrian graphs . in @xcite , mohnke proved that the borromean rings and the whithead link can not be represented by legendrian links of _ trivial unknots _ , that is unknots with @xmath1 and @xmath2 . the trivial unknot is the one unknot among all unknots that attains the maximal thurston - bennequin number of its topological class . as an application of our invariants , we ask which graphs admit legendrian embeddings with all cycles trivial unknots . in section [ maxtb ] , we give a full characterization of these graphs , in the form of the following : a graph @xmath10 admits a legendrian embedding in @xmath0 with all its cycles trivial unknots if and only if @xmath10 does not contain @xmath3 as a minor . the proof of this theorem relies partly on the fact that the trivial unknot has an odd thurston - bennequin number , that is @xmath1 . we prove the reverse implication in more generality , for @xmath11 which represents the set of topological knot classes with odd maximal thurston - bennequin number . let @xmath10 be a graph that contains @xmath3 as a minor . there does not exist a legendrian realization of @xmath10 such that all its cycles are knots in @xmath12 realizing their maximal thurston - bennequin number . it is known that certain legendrian knots and links are determined by the invariants @xmath7 and @xmath8 : the unknot ( see @xcite ) , the torus knots and the figure eight knot ( see @xcite ) , the links consisting of an unknot and a cable of that unknot ( see @xcite ) . in section [ classification ] , we ask what types of spatial graphs are classified up to legendrian isotopy by the pair @xmath4 . we show that the pair @xmath4 does not classify graphs which contain both cycles and either cut vertices or cut edges , independent of the chosen topological class . this means that even uncomplicated graphs carry more information than the set of knots represented by their cycles . in order to have a classification by the pair @xmath4 , we must first narrow to a specific topological class . we investigate _ topological planar graphs _ , that is an embedded graph that is ambient isotopic to a plannar embedding . not to be confused with _ planar graphs _ , which refers to an abstract graph that has a planar embedding . in the case of the handcuff graph , for topological planar graphs , we prove there are exactly four legendrian realizations for each pair @xmath4 . for the lollipop graph , for topological planar graphs , we prove there are exactly two legendrian realizations for each pair @xmath4 . the authors would like to thank tim cochran for his support and interest in the project . they would also like to thank john etnyre for helpful conversations .	we investigate legendrian graphs in . we extend the classical invariants , thurston - bennequin number and rotation number to legendrian graphs . we prove that a graph can be legendrian realized with all its cycles legendrian unknots with and if and only if it does not contain as a minor .	we investigate legendrian graphs in . we extend the classical invariants , thurston - bennequin number and rotation number to legendrian graphs . we prove that a graph can be legendrian realized with all its cycles legendrian unknots with and if and only if it does not contain as a minor . we show that the pair does not characterize a legendrian graph up to legendrian isotopy if the graph contains a cut edge or a cut vertex . for the lollipop graph the pair determines two legendrian classes and for the handcuff graph it determines four legendrian classes .
1106.4320	c	we have investigated signals of nucleon destruction that can arise in specific theories where dark matter is antibaryonic . antibaryonic dm is motivated by unified mechanisms for dm and baryon generation ( referred to as hylogenesis ) which address the cosmic coincidence between the energy densities of dark and visible matter in the universe . in the hylogenesis scenario considered here , the dm consists of an asymmetric density of fermions @xmath11 and scalars @xmath12 . these particles can scatter inelastically with nucleons via the reactions @xmath321 and @xmath322 , where @xmath30 is a nucleon and @xmath27 is a meson . these induced nucleon decay ( ind ) processes lead to distinctive signatures in nucleon decay searches , stellar evolution , and hadron colliders . ind is a novel signature of dm that can be searched for in terrestrial nucleon decay searches . the effective nucleon lifetime is expected to be @xmath323 years , if baryon transfer between dark and visible sectors is mediated by new physics at a scale @xmath324 . since the dm states are unobserved , ind events mimic standard nucleon decay with neutrino final states , but typically with greater final state meson energy @xmath325 . due to these different kinematics , existing searches do not directly apply in general . our study therefore motivates new searches in these experiments . we expect that the resulting sensitivities should be comparable to those in standard nucleon decay searches . the coupling of hylogenic dm to quarks responsible for ind can also give rise to observable signals in hadron colliders . in particular , such couplings can potentially lead to monojet signals at the tevatron and the lhc . existing monojet searches at the tevatron place a lower bound on the coupling of hylogenic dm to quarks , and this bound will be significantly improved at the lhc . we find that the coupling strengths that can be probed at the lhc are of the same size as those that can produce an observable effect in nucleon decay search experiments . this correlation may permit the characterization of hylogenic dm through a very diverse set of experimental probes . if hylogenic dm also scatters elastically with nucleons , it can be captured in stars . once captured , it will thermalize with the baryons in the star and sink to the stellar core . in compact stars , the local baryon density in the stellar core may be large enough for ind to occur at a significant rate , destroying both a nuclon and the hdm particle , and producing an anti - hdm particle and a meson . this process deposits energy in the star , an effect that may be probed by observing old and cool neutron stars or white dwarfs . however , current observations do not provide a definitive bound on or evidence for these processes .	we investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number , as may occur when the dark matter abundance is linked to the baryon abundance . these processes lead to an effective nucleon lifetime of years in terrestrial nucleon decay experiments , if baryon number transfer between visible and dark sectors arises through new physics at the weak scale .	we investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number , as may occur when the dark matter abundance is linked to the baryon abundance . antibaryonic dark matter can cause _ induced nucleon decay _ by annihilating visible baryons through inelastic scattering . these processes lead to an effective nucleon lifetime of years in terrestrial nucleon decay experiments , if baryon number transfer between visible and dark sectors arises through new physics at the weak scale . the possibility of induced nucleon decay motivates a novel approach for direct detection of cosmic dark matter in nucleon decay experiments . monojet searches ( and related signatures ) at hadron colliders also provide a complementary probe of weak - scale dark - matter induced baryon number violation . finally , we discuss the effects of baryon - destroying dark matter on stellar systems and show that it can be consistent with existing observations . baryon destruction by asymmetric dark matter hooman davoudiasl , david e. morrissey , kris sigurdson , sean tulin + department of physics , brookhaven national laboratory , + upton , ny 11973 , usa + theory group , triumf , + 4004 wesbrook mall , vancouver , bc v6 t 2a3 , canada + department of physics and astronomy , university of british columbia , + vancouver , bc v6 t 1z1 , canada + email : hooman@bnl.gov , dmorri@triumf.ca , krs@physics.ubc.ca , tulin@triumf.ca
0801.3305	r	figure [ fig:4 ] shows the gas structure around the hill sphere for model m04 at @xmath186 . figure [ fig:4 ] left panel shows the structure on the cross section in the @xmath187 plane , in which red lines indicate the streamlines . in this panel , the gas enters @xmath188 grid from upper @xmath83 boundary for @xmath189 ( from lower @xmath83 boundary for @xmath190 ) and goes downward ( upward for @xmath190 ) according to the keplerian shear motion . the shocks ( crowded contours near the hill radius ) are seen in the upper right and lower left region from the protoplanet . in this model , the shock front almost corresponds to the hill radius ( fig . [ fig:4 ] left panel ) . when the gas approaches the protoplanet , the streamlines are bent by the gravity of the protoplanet . according to @xcite , the gas flow is divided into three region : the pass - by region ( @xmath191 ) , the horseshoe region ( @xmath192 , and @xmath193 ) , and the planet atmosphere region ( @xmath194 ) . note that although @xcite classified the flow pattern in their two dimensional calculation , their classification is useful for global flow pattern in three dimensions . in the pass - by region , the flow is first attracted toward the protoplanet , and then causes a shock after passing by the protoplanet . at the shock front , the density reaches a local peak and the streamlines bend suddenly . on the other hand , the gas entering the horseshoe region turns round by the coriolis force and goes back . the outermost streamlines in the horseshoe region ( i.e. , the streamlines passing very close to the protoplanet ) pass through the shock front , while the gas on the streamlines far from the protoplanet does not experience the shock . in the atmospheric region , the gas is bound by the protoplanet and forms a circumplanetary disk that revolves circularly around the protoplanet in the prograde ( counterclockwise ) direction . although the streamlines on @xmath187 plane ( fig . [ fig:4 ] left panel ) are similar to those in recent two dimensional calculations ( e.g. , * ? ? ? * ; * ? ? ? * ) , there are important differences . in two - dimensional calculations , a part of the gas near the hill sphere can accrete onto the protoplanet . @xcite showed that gas only in a narrow band that distributed from the lower left to the upper right region against the protoplanet for @xmath128 spirals inward toward the protoplanet passing through the shocked region and finally accretes onto the protoplanet ( for details , see figs . 4 , and 8 of * ? ? ? * ) . on the other hand , in our three - dimensional calculation , gas only flows out from the hill sphere and thus does not accrete onto the protoplanet on the midplane . figure [ fig:4 ] left panel shows that although gas flows into the hill sphere , a part of the gas flows out from the central region . figure [ fig:4 ] right panel is three - dimensional view at the same epoch as the left panel . in this panel , only the streamlines flowing into the high - density region of @xmath195 are drawn for @xmath196 which are inversely integrated from the high - density region . this panel clearly shows the gas flowing into the protoplanet in the vertical direction . to investigate gas flowing into the protoplanet system in detail , in figure [ fig:5 ] , we plot the streamlines at the same epoch as figure [ fig:4 ] with different grid levels ( @xmath93=3 , 5 , and 7 ) . in this figure , each upper panel shows three - dimensional view , while each lower panel shows the structure on the cross section in the @xmath197 plane . note that , in lower panels , the streamlines are projected onto the @xmath197 plane . figure [ fig:5]_a _ shows only the streamlines in a narrow bundle flowing into the protoplanet system . this feature is similar to that shown in two - dimensional calculations @xcite . however , the streamlines in figure [ fig:5]_a _ indicate that gas rises upward near the shock front and then falls into the central region in the vertical direction . gas flowing in the vertical direction spirals into the inner region ( fig . [ fig:5]_c _ ) . in this process , vortices appear as shown in figure [ fig:5]_d_. as shown in figure [ fig:4 ] left panel , also in figure [ fig:5]_d _ , gas is flowing out from the central region on @xmath187 plane . gas in the proximity of the protoplanet rotates circularly in the prograde direction as shown in figure [ fig:5]_e_. figure [ fig:5]_f _ shows that a part of the gas flowing into the upper boundary of @xmath198 grid level contributes to the disk formation around the protoplanet , while a remainder is bent and flows out from the central region . when we look down the protoplanetary disk from the above along the @xmath84-axis , streamlines may seem to be almost the same as those in two - dimensional calculations . however , gas moves also in the vertical direction : streamlines go upward near the shock front ( @xmath199 ) , and vertically falls into the central region at @xmath195 . this feature of streamlines is also seen in models m04s01 and m04s03 , in which the sink cell is adopted . thus , different features of streamlines in two- and three - dimensional calculations are not caused by the effect of the pressure gradient force , but caused by the dimensions ( because the same feature appears in both models with and without the sink ) . this flow pattern is also seen in other three - dimensional calculation @xcite . in two - dimensional calculation , since the vertical motion is restricted , the flow pattern is different from that in three dimensions . this difference affects the accretion rate onto the protoplanet and migration rate . @xcite showed that the migration rate is different between two- and three - dimensional calculations . in the present study , however , since we focus on the angular momentum of a protoplanet system , we do not discuss them any more . we will discuss the accretion and migration rate in the subsequent papers . finally , we comment on the circumplanetary disk . in figure [ fig:5 ] lower panels , the green surface ( i.e. , iso - density surface ) indicates the high - density structure around the protoplanet . these panels show the disk - like structure in the proximity of the protoplanet , and the disk becomes thinner as it approaches the protoplanet ( i.e. , the origin ) . we discuss the circumplanetary disk in [ sec : dis - disk ] . we have shown the evolution of the protoplanet system for model with 0.4@xmath2 in [ sec : typical ] . in this subsection , we investigate the evolution of the protoplanet system with different protoplanet masses . figure [ fig:6 ] upper panels show the accumulated masses ( eq . [ eq : mr ] ) within @xmath200 ( @xmath201 , fig . [ fig:6]_a _ ) and @xmath202 ( @xmath203 , fig . [ fig:6]_b _ ) against the elapsed time for different models , while figure [ fig:6 ] middle panels show the corresponding angular momenta ( eq . [ eq : jr ] ) in the same regions ( fig . [ fig:6]_c _ for @xmath204 , and fig . [ fig:6]_d _ for @xmath205 ) . in figure [ fig:6 ] , both masses and angular momenta for all models increase rapidly for @xmath206 . this is because the protoplanet with mass of @xmath207 suddenly appears in the protoplanetary disk at @xmath208 . however , this rapid growth phase ( @xmath206 ) is not real , because the gas is considered to begin to accrete onto the protoplanet when the mass of the solid core exceeds @xmath6 @xcite . the growth rates of the mass and angular momentum begin to decrease at @xmath209 in all models , then both masses and angular momenta increase with an almost constant rate until the end of the calculation ( @xmath210 ) . @xcite calculated the mass accretion rate onto the protoplanet as @xmath211 thus , the growth time @xmath212 is @xmath213yr ( i.e. , @xmath214 ) . in our calculation , we continue to calculate the evolution of the protoplanet system for @xmath215yr ( @xmath216 ) by fixing the planet mass . we think that this treatment is not problematic , since the growth timescale is longer than our calculation time . note that since @xcite calculated the evolution of the protoplanet system in two dimensions , the growth rate might be different from that in three - dimensional calculations . figure [ fig:6 ] lower panels show the evolution of the average specific angular momentum in the region of @xmath200 ( fig . [ fig:6]_e _ for @xmath217 ) and @xmath202 ( fig . [ fig:6]_f _ for @xmath218 ) . the masses and angular momenta flowing into the protoplanet system increase with a constant rate for @xmath206 , while the average specific angular momenta are saturated at certain values for @xmath219 . this saturation means that flow around the protoplanet is in the steady state . figures [ fig:6]_e _ and _ f _ also indicate that the average specific angular momentum brought into the protoplanet system increases with the mass of the protoplanet . in figures [ fig:6]_e _ and _ f _ , the average specific angular momenta in the region of @xmath200 is larger than those in the region of @xmath202 indicating that the protoplanet system has a larger average specific angular momentum in the more distant place from the protoplanet . we will investigate the angular momentum acquired in the protoplanet system in [ sec : dis - evo ] . figures [ fig:7 ] and [ fig:8 ] show the density distributions ( upper panels ) and jacobi energy contours ( lower panels ) on the cross section in the @xmath187 ( fig . [ fig:7 ] ) and @xmath197 plane ( fig . [ fig:8 ] ) around the hill sphere after the steady state is achieved ( @xmath220 ) for models m02 ( left panels ) , m04 ( middle panels ) , and m06 ( right panels ) . the white - dotted line in each panel indicates the hill radius @xmath71 . in each upper panel , the shock appears from the upper left to lower right near the hill radius . these shocks are frequently seen in similar calculations @xcite . in figure [ fig:7 ] upper panels , the round structures are seen in the proximity to the protoplanet ( @xmath195 ) , while the ellipsoidal structures are seen in the regions of @xmath221 . this is because gas distributed near the protoplanet is more strongly bound by the protoplanet . figure [ fig:8 ] upper panels show that contours of the central region sags in the center of a concave structure , and thin disks are formed around the protoplanet ( @xmath195 ) . in addition , the butterfly - like structure is also seen inside the hill radius in figure [ fig:8 ] upper panels . these structures are considered to be formed by the rapid rotation of the central circumplanetary disk : similar structure is seen in a rapidly rotating protostar ( e.g. , fig.1 of * ? ? ? we will discuss the disk structure in [ sec : dis - disk ] . in contrast to celestial mechanics , it is difficult to find fluid elements bound by the protoplanet because thermal energy is important in addition to the gravitational and kinetic energies . to discern gas bound by the gravity of the protoplanet , we use the jacobi energy as an indicator @xcite . in our unit , the jacobi energy is given by @xmath222 in equation ( [ eq : jacobi ] ) , the first term is the kinetic energy , the second and third terms are the tidal energy of the central star , and the forth term is the gravitational energy of the protoplanet . the jacobi energy is the conserved quantity in a rotating system . in the case of fluid , the jacobi energy is not strictly appropriate because the thermal energy is ignored . however , we can use this for rough estimation of gas bound by the protoplanet . we determine fluid elements bound by the protoplanet from the contour of the jacobi energy in the lower panels in figures [ fig:7 ] and [ fig:8 ] . fluid elements with lower jacobi energy are strongly bound by the protoplanet as described in equation ( [ eq : jacobi ] ) . lower panels of figures [ fig:7 ] and [ fig:8 ] show that inside the region of @xmath223 , each contour has a closed ellipse . since fluid elements move on this closed orbit , it is considered that gas distributed in the region of @xmath223 is bound by the protoplanet when the thermal effect can be ignored . we discuss the thermal effect in [ sec : dis - evo ] . on the other hand , although fluid elements exist inside the hill radius , outside @xmath224 , they are not bound by the protoplanet , because the contours of the jacobi energy straddle the hill radius . for example , in lower left panel of figure [ fig:7 ] , the contour of @xmath225 straddle the hill radius , and thus fluid elements with this jacobi energy freely move on this contour . thus , although these elements transiently stay inside the hill radius , they flow out from the hill sphere . in summary , figures [ fig:7 ] and [ fig:8 ] suggest that fluid elements inside @xmath226 are bound by the protoplanet . figure [ fig:9 ] upper panel shows the accumulated mass @xmath227 for different models after the steady state is achieved ( @xmath174 ) . in this panel , a thin solid line indicates the initial value ( or the value of the protoplanetary disk ) , and the circle is the hill radius @xmath228 for each model . the accumulated mass in any model is larger than the initial value , because gas flows into the hill sphere . this panel indicates that the massive protoplanet has a massive envelope . since these mass distributions are in a steady state at the fixed mass of the protoplanet , it can be considered that different curves correspond to snapshots at different evolution phases . namely , a gas envelope increases its mass with time ( or the protoplanet mass ) . outside the hill radius , the accumulated mass in each model converges to the initial value indicating that the mass distribution for @xmath229 does not change from the initial state because the influence of the protoplanet is small . figure [ fig:9 ] lower panel shows the absolute value of the angular momentum @xmath230 . there are spikes in all models , at which the sign of the angular momentum is reversed . as shown in [ sec : sink ] , the angular momentum has a positive sign around the protoplanet ( @xmath231 ) , while it becomes negative outside the hill radius ( @xmath229 ) . the sign of the angular momentum is reversed outside the hill radius for models m01 , m02 , m04 , and m06 , while it is reversed inside the hill radius for model m005 . this is because the protoplanet system for model m005 does not acquire a sufficient mass and angular momentum owing to the shallow gravitational potential and relatively large thermal pressure ( for details , see [ sec : dis - evo ] ) . figure [ fig:9 ] upper panel shows that the protoplanet system has the envelope mass of only @xmath232 for model m005 , in which the protoplanet mass is @xmath233 . except for model m005 , the angular momenta gradually decrease after they reach their peak around @xmath234 , then it becomes negative at @xmath235 . thus , the angular momenta bound by the protoplanet system are limited in the region of @xmath236 at the maximum . figure [ fig:9 ] lower panel shows that the angular momentum keeps an almost constant value around the hill radius ( @xmath237 ) , until they are reversed . this means that the angular momentum with plus sign and that with minus sign are mixed in this region , as shown in figure [ fig:4 ] left panel . as a result , wherever we estimate the angular momentum in the range of @xmath238 , we can obtain almost the same values of the angular momentum . the distributions of the average specific angular momentum @xmath175 for different models are shown in figure [ fig:10 ] . the circles in this figure mean the hill radii @xmath228 . the crosses indicate the jacobi radii @xmath239 inside which gas is considered to be bound by the gravity of the protoplanet . we determine the jacobi radii from the contour of the jacobi energies as in figures [ fig:7 ] and [ fig:8 ] lower panels . the jacobi radii in all models are distributed in the range of @xmath240 . figure [ fig:10 ] indicates that a more massive protoplanet has an envelope with larger amount of the specific angular momentum . thus , the specific angular momentum accreting onto the protoplanet system increases as the protoplanet mass increases . the rapid drops at large radii indicate the reverse of the rotation axis as shown in figures [ fig:3 ] and [ fig:9 ] . in figure [ fig:10 ] , in model m01 ( @xmath241 ) , @xmath175 at @xmath180 is twice of that at @xmath242 , while , in models m02 , m04 , m06 , m1 , and m3 ( @xmath243 ) , there are little differences between the average specific angular momentum derived from the hill radius @xmath244 and that derived from jacobi radius @xmath245 . thus , we can safely estimate the average specific angular momentum using either the hill radius or jacobi radius for models with @xmath246 . to properly calculate the angular momentum of the protoplanet system , we have to calculate the planetary growth from the solid core with @xmath6 to the present mass . however , it takes huge computation time to calculate all evolution phases . thus , we estimate the angular momentum of the protoplanet system according to the following procedure : ( i ) we calculate the average specific angular momenta of the gas flowing into the protoplanet system at the fixed masses of the protoplanet ( i.e. , under the same parameter @xmath71 ) in models changing the mass of the protoplanet , then ( ii ) derive the relation between the average specific angular momentum and mass of the protoplanet , and describe it as a function of the protoplanet mass , and ( iii ) estimate the angular momentum of the protoplanet system integrating the average specific angular momentum by mass up to the present value of gas giant planets . at first , we analytically estimate the specific angular momentum of the protoplanet system , then compare it with numerical results . we assume that the gas that overcomes the hill potential flows into the hill sphere ( or a protoplanet system ) with the kepler velocity of the protoplanet at the hill radius @xmath228 . when the protoplanet mass is @xmath0 , the kepler velocity at @xmath228 is given by @xmath247 note that @xmath248 is constant when @xmath33 is fixed . the specific angular momentum can be written as @xmath249 thus , the specific angular momentum is proportional to @xmath250 . in addition , when the mass of the central star is fixed , the specific angular momentum is proportional to @xmath251 thus , the specific angular momentum increases with 2/3 power of the protoplanet mass . figure [ fig:11 ] shows the average specific angular momentum derived from all models against the protoplanet mass . the average specific angular momenta are estimated in the region of @xmath252 ( @xmath253 ) , @xmath254 ( @xmath255 ) , @xmath256 ( @xmath257 ) , and @xmath258 ( @xmath259 ) . although we fixed the protoplanet mass in each model , we can consider the horizontal axis in figure [ fig:11 ] as time sequence of the protoplanet system . figure [ fig:11 ] clearly shows that more massive protoplanet can acquire the envelope with larger average specific angular momentum . although the average specific angular momenta for @xmath260 differ from those for @xmath261 for models with @xmath262 , there are little difference for models with @xmath263 . in addition , when we adopt the average specific angular momenta in the region of @xmath264 , we underestimate them for any model as shown in figure [ fig:11 ] . therefore , we can properly estimate the average specific angular momentum of the protoplanet system in any region of @xmath265 for models with @xmath266 . in figure [ fig:11 ] , the red and blue lines are fitting formulae of the evolution of the average specific angular momentum as a function of the protoplanet mass for @xmath267 ( low mass , @xmath268 ; red line ) , and @xmath269 ( high mass , @xmath270 : blue line ) . they are given by @xmath271 and @xmath272 figure [ fig:11 ] shows that the evolution of the average specific angular momentum for @xmath273 is well described by @xmath274 which corresponds to the equation ( [ eq : ana - j ] ) . on the other hand , the growth rate of the average specific angular momentum for @xmath275 is larger than @xmath274 , and can be fitted by @xmath3 . we ignored the thermal effect when we derive equation ( [ eq : ana - j ] ) . when @xmath0 is small , the gas flowing into the protoplanet system is affected relatively strongly by the thermal pressure . we can estimate the mass at which the gravity dominates the thermal pressure force from the balance between the thermal pressure gradient and gravitational forces . near the hill radius , the thermal pressure gradient force is more dominant than the gravity when the kepler speed is slower than the sound speed ( i.e. , @xmath276 ) . on the other hand , when @xmath277 , the gas flow is controlled mainly by the gravity of the protoplanet even near the hill radius . using equation ( [ eq : kepler ] ) , @xmath278 is realized when @xmath279 which corresponds to @xmath280 of the protoplanet mass at @xmath79au . thus , the gas flow is largely affected by the thermal pressure for @xmath281 , while it is not so affected by the thermal pressure for @xmath282 . in figure [ fig:11 ] , the evolution of the angular momentum for @xmath283 well corresponds to the analytical solution ( @xmath4 ) indicating that the thermal effect is negligible for @xmath284 . however , for @xmath285 , the average specific angular momentum is smaller than @xmath270 ( blue line ) . thus , when the protoplanet is @xmath275 , the thermal effect is not negligible for the acquisition process of the angular momentum because the gravitational potential is relatively shallow . thus , the thermal pressure seems to remain important for @xmath286 , although @xmath278 realized at @xmath287 . to verify the relation of the thermal and gravitational effects , in figure [ fig:12 ] , we plot the ratio of the azimuthal to kepler velocity ( @xmath288 ) around the protoplanet on the midplane for models m02 , m04 , and m06 . in this figure , closed contours inside the hill radius indicate that gas revolves around the protoplanet . for example , the closed contour of @xmath289 in figure [ fig:12 ] means that gas rotates along the contour with 50% of the kepler velocity . the black circles represent contours of @xmath290 , inside which gas revolves around the protoplanet with supersonic velocity . thus , the gravitational force of the protoplanet is dominant inside the black circles , while the thermal pressure gradient force is dominant outside the black circles . figure [ fig:12 ] shows that the radius of the @xmath290 contour increases with the protoplanet mass indicating that the region that dominated by gravity of the protoplanet extends with the protoplanet mass . as the protoplanet mass increases , the flow speed inside the hill radius approaches to the kepler velocity , and the region dominated by the gravity of the protoplanet spreads outward . in this way , since the thermal effect decreases as the protoplanet mass increases , the growth rate of the average specific angular momentum approaches to the analytical solution ( eq . [ eq : ana - j ] ) .	we find that the gas flows onto the protoplanet system in the vertical direction crossing the shock front near the hill radius of the protoplanet , which is qualitatively different from the picture established by two - dimensional simulations . the specific angular momentum of the gas accreted by the protoplanet system increases with the protoplanet mass . at jovian orbit , when the protoplanet mass is , where is jovian mass , the specific angular momentum increases as . on the other hand , it increases as when the protoplanet mass is . the stronger dependence of the specific angular momentum on the protoplanet mass for is due to thermal pressure of the gas . the estimated total angular momentum of a system of a gas giant planet and a circumplanetary disk is two - orders of magnitude larger than those of the present gas giant planets in the solar system . we also discuss the satellite formation from the circumplanetary disk .	we investigate the accretion of angular momentum onto a protoplanet system using three - dimensional hydrodynamical simulations . we consider a local region around a protoplanet in a protoplanetary disk with sufficient spatial resolution . we describe the structure of the gas flow onto and around the protoplanet in detail . we find that the gas flows onto the protoplanet system in the vertical direction crossing the shock front near the hill radius of the protoplanet , which is qualitatively different from the picture established by two - dimensional simulations . the specific angular momentum of the gas accreted by the protoplanet system increases with the protoplanet mass . at jovian orbit , when the protoplanet mass is , where is jovian mass , the specific angular momentum increases as . on the other hand , it increases as when the protoplanet mass is . the stronger dependence of the specific angular momentum on the protoplanet mass for is due to thermal pressure of the gas . the estimated total angular momentum of a system of a gas giant planet and a circumplanetary disk is two - orders of magnitude larger than those of the present gas giant planets in the solar system . a large fraction of the total angular momentum contributes to the formation of the circumplanetary disk . we also discuss the satellite formation from the circumplanetary disk .
1601.07675	i	the complex behavior of mixtures of bosonic gases has been extensively investigated experimentally in particular , in cold - atom systems @xcite and theoretically @xcite . these systems exhibit a rich behavior , at zero and finite temperature , with several different phases separated by transition lines , along which one or more components of the system undergo bose - einstein condensation ( bec ) . in this paper we consider three - dimensional ( 3d ) mixtures of two different bosonic gases with short - range interactions that only depend on the local densities of the two gases . the hamiltonian of these systems is invariant under u(1 ) transformations acting independently on each species , so that the model is u(1)@xmath0u(1 ) symmetric . in particular , we consider the 3d two - component bose - hubbard model with an on - site inter - species density - density interaction . this is a realistic model for two bosonic species in optical lattices @xcite . we determine the finite - temperature phase diagram by using a variety of techniques . first , we consider the mean - field ( mf ) approximation , determining the qualitative phase behavior of the system as a function of the model parameters , such as the chemical potentials and the on - site inter- and intra - species couplings . we find several different phases , in which each species may be in the normal or superfluid state , and identify critical lines and multicritical points ( mcps ) where some transition lines meet . the 3d phase diagram is investigated in the hard - core ( hc ) limit of each species by a finite - size scaling ( fss ) analysis of quantum monte carlo ( qmc ) simulations . the numerical data allows us to identify the universality class of the transition lines that correspond to the bec of one of the two species . we show that , independently whether the noncritical component is in the normal or superfluid phase , the critical behavior of the condensing species belongs to the 3d xy universality class characterized by the breaking of a global u(1 ) symmetry and by short - range effective interactions . this is the same universality class associated with the bec of a single bosonic gas @xcite ( and also with the superfluid transition in @xmath3he @xcite , with transitions in some liquid crystals characterized by density or spin waves and in magnetic systems with easy - plane anisotropy , etc . this result implies an effective decoupling of the critical modes of the condensing species from those of the noncritical component , independently whether the latter is in the normal or superfluid phase . the phase diagram of mixtures of bosonic gases also presents particular points where some transition lines meet . multicritical behaviors develop at these mcps , arising from the competition of the two u(1 ) order parameters associated with the bec of the two species . to identify the possible universality classes of the multicritical behaviors , we use the field - theoretical approach , considering the effective landau - ginzburg - wilson ( lgw ) @xmath1 theory for two complex fields with global u(1)@xmath0u(1 ) symmetry . we study the renormalization - group ( rg ) flow in the quartic - parameter space , identifying the stable fixed points ( fps ) , which control the critical behavior , and their attraction domain . the paper is organized as follows . in sec . [ model ] we define the bose - hubbard model for two lattice bosonic gases . in sec . [ phmf ] we determine the phase diagram of the model in the mf approximation , showing that , by changing the model parameters , one can obtain qualitatively different behaviors . in sec . [ critbeh ] we present our numerical results and determine numerically the critical behavior along the transition lines where one species undergoes bec . in sec . [ multi ] we study the multicritical behaviors at mcps where some transition lines meet in the phase diagram . finally , in sec . [ conclu ] we draw our conclusions . [ 5loop ] reports the five - loop perturbative series of the minimal - subtraction scheme , which are used in the rg study of the multicritical behavior .	we study the phase diagram and the critical behaviors along the transition lines characterized by the bose - einstein condensation of one or both species . we present mean - field calculations and numerical finite - size scaling analyses of quantum monte carlo data . we determine the possible multicritical behaviors by using field - theoretical perturbative methods .	we investigate the bose - einstein condensation patterns , the critical and multicritical behaviors of three - dimensional mixtures of bosonic gases with short - range density - density interactions . these systems have a global u(1)u(1 ) symmetry , as the system hamiltonian is invariant under independent u(1 ) transformations acting on each species . in particular , we consider the three - dimensional bose - hubbard model for two lattice bosonic gases coupled by an on - site inter - species density - density interaction . we study the phase diagram and the critical behaviors along the transition lines characterized by the bose - einstein condensation of one or both species . we present mean - field calculations and numerical finite - size scaling analyses of quantum monte carlo data . we also consider multicritical points , close to which it is possible to observe the condensation of both gas components . we determine the possible multicritical behaviors by using field - theoretical perturbative methods . we consider the u(1)u(1)-symmetric landau - ginzburg - wilson theory and determine the corresponding stable fixed points of the renormalization - group flow . the analysis predicts that , in all cases , the multicritical behavior is analogous to the one that would be observed in systems of two identical gases , with an additional exchange symmetry .
1601.07675	c	in this paper we study the critical and multicritical behaviors that can be observed in 3d mixtures of bosonic gases interacting by short - range density - density interactions . these systems have a global u(1)@xmath0u(1 ) symmetry , related to independent u(1 ) transformations acting on each species . as a representative of this class of systems , we consider the 3d bose - hubbard model for two lattice bosonic gases coupled by an on - site inter - species density - density interaction , whose hamiltonian is given in eq . ( [ sbh ] ) . however , the qualitative features of the finite - temperature phase diagram and the results for the universality classes associated with the critical and multicritical behaviors apply to generic bosonic mixtures . the generic features of the phase diagram of the 2bh model have been determined in the mf approximation and additionally confirmed by qmc simulations . the qualititave behavior depends on the model parameters , such as the chemical potentials and the on - site inter- and intra - species couplings . by varying them , one can observe several transition lines , along which one of the two species undergoes a normal - to - superfluid transition , and different types of multicritical behavior . the transition lines separating the different phases generally correspond to the bec condensation of one of the two species . we show that , independently whether the other species is in the normal or superfluid phase , the critical behavior of the condensing species belongs to the 3d xy universality class , characterized by the breaking of a global u(1 ) symmetry and short - ranged effective interactions , which is the same universality class associated with the bec of a single bosonic gas . therefore , the critical modes of the condensing gas effectively decouple from those of the other species , independently whether the latter is in the normal or superfluid phase . the phase diagram of mixtures of bosonic gases also presents particular points where some transition lines meet . at these points multicritical behaviors develop , due to the competition of the u(1 ) order parameters related to the two bosonic gases . we investigate them by a field - theoretical approach based on the effective lgw @xmath1 theory for two complex scalar fields with global u(1)@xmath0u(1 ) symmetry . the possible universality classes that describe the multicritical behaviors are associated with the stable fps of the rg flow . they can be determined by studying the rg trajectories in the critical theory , starting from the unstable gaussian fp in the quartic - parameter space . for this purpose , we consider the so - called @xmath223 scheme without @xmath222 expansion @xcite . we start from the five - loop @xmath340 @xmath221 functions , resum them using the pad - borel technique , and solve the flow equations . we find two stable fps , that also belong to the @xmath1 theory ( [ phi4s ] ) , which has an additional @xmath2 symmetry related to the exchange of the two order parameters . this more symmetric model has already been discussed in the context of the critical behavior of a mixture of two identical gases @xcite . if the system has a tetracritical continuous transition , see fig . [ mcpd ] , the critical behavior is controlled by a decoupled fp . each component shows an xy critical behavior correspondingly , the rg dimensions of the two relevant operators are @xmath341 but with very slowly - decaying scaling corrections ( they decay as @xmath342 , where @xmath184 is the correlation length ) due to inter - species coupling . if , instead , the system undergoes a bicritical continuous transition , the critical behavior is associated with a different asymmetric fp , with @xmath343 and @xmath344 . recent experiments on atomic gas mixtures @xcite , either using two different atomic species or the same atomic species in two different states , have already obtained several interesting results on the properties of the low - temperature condensed phase and on the interplay of the different condensates . they have also demonstrated the possibility of a robust control of the model parameters , which may allow the observation of the different phases , such as those found in the present study , and the determination of the nature of the critical and multicritical behaviors . our results should provide a complete characterization of the possible bec patterns and of the critical behaviors that these systems may develop along their transition lines . most cold - atom experiments have been performed in inhomogeneous conditions , due to the presence of space - dependent trapping forces , which effectively confine the atomic gas within a limited space region @xcite . the trapping potential is effectively coupled to the particle density , which may be taken into account by adding a further hamiltonian term to the 2bh hamiltonian ( [ sbh ] ) , i.e. , @xmath345 where @xmath65 is the space - dependent potential associated with the external force . the inhomogeneity arising from the trapping potential introduces an additional length scale @xmath346 into the problem , which drastically changes the general features of the behavior at the phase transitions . experimental data for inhomogeneous trapped cold - atom systems are usually analyzed using the local - density approximation , see , e.g. , ref . . however , this approach fails to describe the emergence of large - scale correlations @xcite . this problem may be overcome experimentally by using ( almost ) flat traps , giving rise to a finite space region where the system is effectively homogenous @xcite . otherwise , one may infer the critical behavior by studying the scaling behavior with respect to the trap size @xmath346 , which is expected to be universal and controlled by the critical exponents of the universality class of the corresponding homogenous system , in the large trap - size limit @xcite .	we investigate the bose - einstein condensation patterns , the critical and multicritical behaviors of three - dimensional mixtures of bosonic gases with short - range density - density interactions . these systems have a global u(1)u(1 ) symmetry , as the system hamiltonian is invariant under independent u(1 ) transformations acting on each species . in particular , we consider the three - dimensional bose - hubbard model for two lattice bosonic gases coupled by an on - site inter - species density - density interaction . we also consider multicritical points , close to which it is possible to observe the condensation of both gas components . the analysis predicts that , in all cases , the multicritical behavior is analogous to the one that would be observed in systems of two identical gases , with an additional exchange symmetry .	we investigate the bose - einstein condensation patterns , the critical and multicritical behaviors of three - dimensional mixtures of bosonic gases with short - range density - density interactions . these systems have a global u(1)u(1 ) symmetry , as the system hamiltonian is invariant under independent u(1 ) transformations acting on each species . in particular , we consider the three - dimensional bose - hubbard model for two lattice bosonic gases coupled by an on - site inter - species density - density interaction . we study the phase diagram and the critical behaviors along the transition lines characterized by the bose - einstein condensation of one or both species . we present mean - field calculations and numerical finite - size scaling analyses of quantum monte carlo data . we also consider multicritical points , close to which it is possible to observe the condensation of both gas components . we determine the possible multicritical behaviors by using field - theoretical perturbative methods . we consider the u(1)u(1)-symmetric landau - ginzburg - wilson theory and determine the corresponding stable fixed points of the renormalization - group flow . the analysis predicts that , in all cases , the multicritical behavior is analogous to the one that would be observed in systems of two identical gases , with an additional exchange symmetry .
1308.1094	l	[ sec : studies ] in this section we develop collider analyses aimed at reconstructing the @xmath30 angle in ( [ eq : thetadef ] ) . from ( [ eq : matrix_element : full ] ) and ( [ eq : greatformula ] ) , the matrix element squared for the @xmath224 decay has a term proportional to @xmath225 : the @xmath30 distribution is thus sensitive to the @xmath0 phase @xmath31 as its minimum is located at @xmath226 . as before , we fix @xmath227 and therefore the only new parameter we introduce is @xmath31 . we implement the @xmath31 phase in ( [ eq : lpheno ] ) and the effective vertices in ( [ eq : m : tau_to_rho - nu ] ) and ( [ eq : m : rho_to_pi - pi ] ) into a feynrules v.1.6.0 @xcite model . we then generate monte carlo events in madgraph 5 @xcite for @xmath228 production at the lhc with @xmath43 tev as well as @xmath229 production at the ilc with @xmath230 gev : in either case , the higgs decays via @xmath231 . in order to retain quantum interference effects , the full @xmath232 body process is simulated . for the lhc study , we also generate a background sample of @xmath233 production with the subsequent decay @xmath234 . we will first study the effectiveness of the @xmath30 distribution at truth level , assuming the neutrino momenta are known : this facilitates a comparison to the @xmath235 variable @xcite , which was previously proposed for studying @xmath0 violation in the higgs coupling to taus . after demonstrating the superior qualities of the @xmath30 variable , we present a sensitivity study for reconstructing @xmath30 at the ilc , where the neutrino four - momentum can be reconstructed up to a two - fold ambiguity . finally , we turn to the lhc , where the neutrinos can not be reconstructed and the irreducible @xmath10 background is significant . in this case , we find that using a collinear approximation @xcite for the neutrino momenta in addition to the standard hard cuts for higgs events still allows the @xmath30 distribution to retain significant discrimination power between different underlying @xmath31 signal models . we do not include pileup or perform any detector simulation in this work , aside from implementing flat efficiencies for @xmath1-tagging for the lhc study . pileup effects are expected to complicate the primary vertex determination necessary for measuring charged pion tracks as well as contribute extra ambient radiation in the electromagnetic calorimeter ( ecal ) , making neutral pion momenta measurements more difficult . furthermore , finite tracking and calorimeter resolutions are expected to smear the @xmath30 distribution . in particular , the ability to distinguish between charged and neutral pion momenta when both pions are overlapping also could affect the @xmath30 measurement . note , however , that because of the magnetic field , the softer @xmath133 and @xmath134 could be separated at the ecal . even if the two pions overlap in the ecal , the @xmath134 momentum can be obtained by subtracting the track momentum from the total momentum measured in ecal , assuming negligible contamination from other sources of energy deposition . we also neglect the neutral pion combinatoric issue , which is justified if the respective parent rho mesons are boosted far apart as a result of the higgs decay . in general , the @xmath133 and @xmath134 coming from the same @xmath92 parent are mostly collinear . this fact has been exploited in the hadronic tau tagging algorithm . for example , the hps algorithm used by cms requires that the charged and neutral hadrons are contained in a cone of the size @xmath236 , where @xmath237 is the transverse momentum of the reconstructed tau @xcite . since the two tau candidates are usually required to be well separated , the combinatorics problem in determining the correct @xmath92 parents can be ignored . recall from ( [ eq : matrix_element : full ] ) and ( [ eq : greatformula ] ) that the minimum of the @xmath30 distribution is located at @xmath238 , and so constructing the @xmath30 distribution allows us to read off the @xmath31 phase of the underlying signal model . in figure [ fig : true_varydelta ] , we show the @xmath30 distribution in @xmath228 events where we have temporarily assumed the neutrinos are fully reconstructed . the various signal models with @xmath239 ( @xmath0-even ) , @xmath240 ( maximal @xmath0 admixture ) , and @xmath241 ( @xmath0-odd ) clearly show the large @xmath242 contribution of the matrix element as seen in ( [ eq : greatformula ] ) . we also superimpose the @xmath30 distribution from @xmath233 event . note that it is flat . clearly , observing the cosine oscillation in experimental data will require both a favorable signal to background ratio as well as a solution for the neutrino momenta that preserves the inherently large amplitude of the @xmath30 oscillation . the @xmath30 distributions ( compare with ( [ eq : greatformula ] ) ) for the higgs with @xmath239 ( @xmath0-even ) , @xmath240 ( maximal @xmath0 admixture ) , and @xmath243 ( @xmath0-odd ) , and the @xmath10 , assuming neutrinos are fully reconstructed . the relative normalization of the @xmath10 line is arbitrary . ] we now compare @xmath30 at truth level with the @xmath235 variable proposed in refs . @xcite : here , @xmath235 is the acoplanarity angle between the decay planes of @xmath244 and @xmath122 in the @xmath245 rest frame . the sign of @xmath235 is defined as the sign of the product of @xmath246 . following @xcite , the events are divided into two classes , @xmath247 and @xmath248 , where the two classes are differ by a @xmath249 phase shift . in order to make a direct comparison with our @xmath30 variable , we combine the @xmath235 distributions of the two classes with a @xmath249 phase shift so the phases of the two classes agree . note that while @xmath235 does not refer to the neutrinos , this classification into the two classes still requires the knowledge of the neutrino momenta ( see ( [ eq : var : y+- ] ) ) . assuming the neutrinos are fully reconstructed , the @xmath30 and @xmath235 distributions for @xmath250 events are shown in figure [ fig : thetavsworek ] with @xmath239 . we readily see that oscillation amplitude of the @xmath30 distribution is larger than that of the acoplanarity angle @xmath235 by about @xmath251 . compared to @xmath235 , the @xmath30 variable thus provides superior sensitivity to the @xmath0 phase @xmath31 . the distributions of our @xmath30 and the @xmath235 variable of ref . @xcite for @xmath239 . the @xmath235 distribution is aggregated from the two @xmath248 and @xmath252 classes as explained in the text to make the direct comparison clearer . ] having considered the case where the neutrinos from the tau decays are fully reconstructed , we next turn to the lepton collider environment , where we will find the neutrinos can be fully reconstructed up to a two - fold ambiguity . at a lepton collider running at @xmath230 gev , such as the ilc , the main production mode for the higgs is via associated production with a @xmath10 boson . our prescribed decay mode for the higgs , @xmath253 , has two neutrinos that escape the detector . we use the known initial four momenta , two tau mass and two neutrino mass constraints to solve for each neutrino momentum component . note we will assume the @xmath10 decays to visible states , which will reduce our event yield by 20% . solving the system of equations for the neutrino momenta gives rise to a two - fold ambiguity , where one solution is equal to the truth input neutrino momenta while the other gives a set of wrong neutrino momenta . note both solutions are consistent with four - momentum conservation and therefore correctly reconstruct the higgs mass . since these solutions are indistinguishable in the analysis , we assign each solution half an event weight . the resulting distribution of @xmath30 for @xmath239 is given in figure [ fig : ilctheta ] , where we superimpose the truth level @xmath30 distribution for @xmath254 events for easy comparison . we can see that the oscillation amplitude at the ilc is degraded from the truth level result by @xmath255 . we also show the reconstructed distribution for @xmath239 , @xmath240 , and @xmath256 in figure [ fig : ilcvarydelta ] . while the two - fold ambiguity for the neutrino momenta solution set does degrade the truth level result , the _ @xmath30 distribution in figure [ fig : ilcvarydelta ] shows significant discrimination power between various @xmath31 signal models . note the amplitude of pseudoscalar distribution ( @xmath256 ) is slightly higher than the scalar amplitude : here , the `` wrong solution '' approximates the correct neutrino momenta on average better than the other @xmath239 or @xmath240 cases . this small effect can be traced back to equation ( [ eq : m : h_to_tautau : higgs_frame ] ) where we derived that a pseudoscalar decays to two taus in the singlet spin state . as a result , in this case the two tau spins point in opposite directions , regardless of the spin quantization axis . in the pseudoscalar case the two tau decays thus tend to occur with opposite orientation and the two neutrinos are slightly more back - to - back and consequently the two solutions for their momenta are closer together . the truth and reconstructed @xmath30 distributions at the ilc for @xmath239 . ] the reconstructed @xmath30 distribution at the ilc for @xmath239 , @xmath257 , and @xmath258 . ] we now discuss the projected ilc sensitivity for measuring @xmath31 . at the ilc , the cross section for @xmath259 production at @xmath230 gev with polarized beams @xmath260 for @xmath261 gev is 0.30 pb @xcite . distribution is insensitive to the polarization of the @xmath262-@xmath263 beams . ] assuming a higgs branching fraction to tau pairs of 6.1% , a @xmath264 branching fraction of 26% , and a @xmath10-to - visible branching fraction of 80% , we calculate the ilc should have 990 events with 1 ab@xmath5 of luminosity . since the solved neutrino momenta correctly reconstruct the higgs mass , the @xmath265 backgrounds are negligible and will be ignored . [ tab : ilc ] to estimate the expected ilc accuracy for measuring @xmath31 , we perform a log likelihood ratio test for the sm hypothesis with @xmath266 against an alternative hypothesis with @xmath267 . in general , the likelihood ratio in @xmath268 bins is given by @xmath269 where @xmath270 , @xmath271 and @xmath272 are the number of background events , signal events assuming @xmath239 , and signal events assuming @xmath267 in bin @xmath273 of the @xmath30 distribution . in our ilc treatment , we neglect @xmath265 and @xmath274 continuum backgrounds and so we set @xmath275 . here , @xmath276 is the usual poisson distribution function , @xmath277 . we parametrize the signal @xmath30 distribution with a @xmath278 fit function , where the offset constant @xmath279 and oscillation amplitude @xmath280 are fixed by the fit of the standard model @xmath30 distribution with @xmath239 , giving @xmath281 and @xmath282 respectively . then , the resulting @xmath283 signal @xmath30 distribution is given by @xmath284 . we construct the binned likelihood bins , though we verified the number of bins is immaterial for our results . ] according to ( [ eq : lr ] ) for various @xmath285 hypotheses to test the discrimination against the sm hypothesis . with 1 ab@xmath5 of ilc luminosity , we find @xmath286 discrimination at @xmath287 , which is a highly promising degree of sensitivity for measuring the @xmath0 phase of the higgs coupling to taus . we summarize our rate estimate and accuracy result in table [ tab : ilc ] . we remark that this sensitivity estimate is only driven by statistical uncertainties , and systematic uncertainties are expected to reduce the efficacy of our result . also , detector resolution effects and sm backgrounds , while expected to be small , will also slightly degrade our projection . based on our results , which surpass earlier accuracy estimates of @xmath39 @xcite , a full experimental sensitivity study incorporating these subleading effects is certainly warranted . we now develop an lhc study for reconstructing the @xmath30 distribution in @xmath250 in the @xmath288 final state . we use the @xmath289 final state for a couple of reasons . first , since hadronic taus can be faked by jets , @xmath290 two hadronic taus faces an immense background from multijet qcd . by requiring another object in the final state , we gain handles to suppress the background . second , the collinear approximation gives ambiguous results if the two taus are back - to - back , so the requirement of an additional object in the event guarantees we are away from this configuration . one option is associated production of a higgs wit a @xmath291 . however this rate is quite small , especially once the branching ratios for @xmath291 into clean final states are taken into account . other possibilities include higgs production via vector boson fusion and in association with a jet . both of these options give promising signal - to - background ratios and both should be considered . for concreteness we will consider @xmath292 here as a demonstration of the feasibility of our technique . as mentioned before , the neutrinos are not reconstructible in the hadron collider environment , and so we will employ the collinear approximation @xcite for the neutrino momenta . in figure [ fig : truthvscollinear ] , we show a comparison between the truth level @xmath30 distribution and the @xmath30 distribution using the collinear approximation for neutrino momenta , for the @xmath239 benchmark . while the collinear approximation reduces the oscillation amplitude of the distribution , the location of the minimum of the distribution does not change . therefore , measuring @xmath31 is a viable possibility at the lhc using the collinear approximation for the neutrino momenta . we remark that in the collinear approximation , @xmath30 is equivalent to the acoplanarity angle @xmath235 @xcite . yet , we are the first feasibility study for measuring @xmath0 violation in the higgs coupling to taus at hadron colliders using prompt tau decays and kinematics . with a more sophisticated scheme than the collinear approximation , the @xmath30 variable will be superior to @xmath235 . the distributions of the truth-@xmath30 and @xmath30 from the collinear approximation for @xmath239 . ] at the lhc , the dominant background for the @xmath293 signal process is the irreducible @xmath294 background , where the @xmath10 decays to the same final state as the higgs . as shown earlier in figure [ fig : true_varydelta ] , the @xmath30 distribution from @xmath10 events is flat : importantly , this is true regardless of possible mass window cuts on the reconstructed @xmath295 resonance . we remark that the @xmath0 phase in the higgs coupling to taus does manifest in the @xmath10@xmath1@xmath1 vertex at one loop . since this effect is suppressed by @xmath296 , whereas the signal to background ratio will be @xmath297 , we can safely ignore the loop induced @xmath0 phase in the @xmath10@xmath1@xmath1 vertex . in addition , we will assume that the qcd background contribution also has a flat @xmath30 distribution , since the qcd contamination in the signal region is not expected to have any particular spin correlations . using our @xmath293 and @xmath294 event samples from madgraph 5 for a 14 tev lhc , we first isolate the signal region with a series of hard cuts . first , we apply a preselection requirement on the leading jet @xmath298 gev with @xmath299 . using mcfm v.6.6 @xcite with these preselection requirements on the leading jet , we obtain a @xmath293 nlo inclusive cross section of 2.0 pb with @xmath23 gev and a @xmath294 nlo inclusive cross section of 420 pb . after applying the appropriate higgs , @xmath10 , and tau branching fractions , we calculate a signal cross section of 8.2 fb and @xmath10 background cross section of 970 fb . , while for the background we use @xmath300 . these scale choices are motivated by agreement with higher order ( nnlo ) calculations ( where they exist ) . ] next , we impose hard kinematic cuts to isolate the signal . motivated by @xcite , we choose the signal region to be : * @xmath301 gev , * @xmath302 gev , * @xmath303 , * @xmath304 gev , where @xmath305 is the reconstructed higgs mass by using the collinear approximation . the hard @xmath305 cut strongly suppresses the @xmath306 background , but is less effective on multijet qcd . to reduce the multijet component and its accompanying uncertainty to less than 10% of the total background we impose a high @xmath307 cut . the net efficiencies for signal and @xmath10 background after these cuts are 18% and 0.24% , respectively . rather than simulate the qcd contribution , we account for qcd contamination in the signal region by increasing the @xmath10 background rate by 10% : a complete treatment of the expected qcd background is beyond the scope of this study . finally , for hadronic @xmath1 tagging efficiency , we consider a standard 50% efficiency and a more optimistic 70% efficiency @xcite . we therefore expect 1100 signal events and 1800 @xmath308 qcd background events with 3 ab@xmath5 of luminosity from the 14 tev lhc , assuming 50% @xmath1 tagging efficiency . these rates are summarized in table [ tab : input ] . [ tab : input ] we note that although we generated signal and background samples independently , there is a small interference between higgs and @xmath10 diagrams in the @xmath309 diagram . our checks of this interference on the @xmath30 distributions for combined signal and background events versus separate signal and background events showed a negligible effect : we thus ignore this interference effect . we now perform a likelihood analysis ( [ eq : lr ] ) to quantify how effectively the @xmath30 distribution distinguishes between signal hypotheses with different @xmath0 phases in the presence of @xmath308 qcd background . first , we test the discrimination between a pure scalar and a pure pseudoscalar @xmath49@xmath1@xmath1 coupling . we find that these two hypotheses can be distinguished at @xmath310 sensitivity with 550 ( 300 ) fb@xmath5 assuming 50% ( 70% ) @xmath1 tagging efficiency . we can attain @xmath311 sensitivity between pure scalar and pseudoscalar couplings with 1500 ( 700 ) fb@xmath5 luminosity assuming 50% ( 70% ) efficiency . we also estimate the possible accuracy for the lhc experiments to measure @xmath31 with an upgraded luminosity of @xmath312 . we adopt the same procedure as with the ilc accuracy estimate described in the previous section , modified to account for the @xmath308 qcd background , which is fixed to be flat in @xmath30 . we find that the accuracy in measuring @xmath31 is @xmath42 ( @xmath44 ) assuming 50% ( 70% ) hadronic @xmath1 tagging efficiency . the scalar versus pseudoscalar discrimination and the accuracy estimates are summarized in table [ tab : lhc ] . [ tab : lhc ] again , these estimates are based only on statistical uncertainties without performing a full detector simulation . the effects from pileup and detector resolution are expected to degrade these projections , but corresponding improvements in the analysis , such as a more precise approximation for the neutrino momenta , improved background understanding ( from other lhc measurements ) or multivariate techniques , could counterbalance the decrease in sensitivity . the promising results of our study strongly motivate a comprehensive analysis by the lhc experiments for the prospect of measuring the @xmath0 phase @xmath31 .	we investigate the lhc and higgs factory prospects for measuring the phase in the higgs-- coupling a new , ideal observable is identified from an analytic calculation for the channel . it is demonstrated to have promising sensitivity at the lhc and superior sensitivity at the ilc compared to previous proposals . it is the first proposal for such a measurement at the lhc . , we project that a 250 gev run with 1 ab luminosity can measure the phase to accuracy .	we investigate the lhc and higgs factory prospects for measuring the phase in the higgs-- coupling . currently this phase can be anywhere between ( even ) and ( odd ) . a new , ideal observable is identified from an analytic calculation for the channel . it is demonstrated to have promising sensitivity at the lhc and superior sensitivity at the ilc compared to previous proposals . our observable requires the reconstruction of the internal substructure of decaying taus but does not rely on measuring the impact parameter of tau decays . it is the first proposal for such a measurement at the lhc . for the 14 tev lhc , we estimate that about 1 ab data can discriminate-even versus-odd at the level . with 3 ab , the phase should be measurable to an accuracy of . at an higgs factory , we project that a 250 gev run with 1 ab luminosity can measure the phase to accuracy .
1503.04578	i	let @xmath4 be some closed orientable surface , bordering a compact inner @xmath5 and outer @xmath6 domains . by @xmath7 we denote a subsurface of @xmath8 , which has two faces @xmath9 and @xmath10 and inherits the orientation from @xmath8 : @xmath10 borders the inner domain @xmath5 and @xmath9 borders the outer domain @xmath11 . @xmath7 has the smooth boundary @xmath12 , which is decomposed into two closed parts @xmath13 , consisting each of finite number of smooth arcs , having in common only endpoints . let @xmath14 , @xmath15 be the unit normal vector field on the surface @xmath7 and @xmath16 be the normal derivative . let us consider the laplace - beltrami operator in @xmath0 written in terms of the gnter s tangent derivatives ( see @xcite for more details ) @xmath17 let @xmath18 , @xmath19 , be the unit normal vector field on the boundary @xmath20 , which is tangential to the surface @xmath7 and directed outside of the surface . and , finally , let @xmath21 be the normal derivative on the boundary of the surface , which is the outer tangential derivative on the surface . we study the following mixed boundary value problem for the laplace - beltrami equation @xmath22 u^+(\tau)=g(\tau ) , \qquad & \tau\in\gamma_d , \\[0.2 cm ] ( \partial_{{{\boldsymbol{\nu}}}_\gamma}u)^+(\tau)=h(\tau),\qquad & \tau\in\gamma_n . \end{array}\right.\end{aligned}\ ] ] where @xmath23 and @xmath24 denote respectively the dirichlet and the neumann traces on the boundary . we need the bessel potential @xmath25 , @xmath26 , @xmath27 and sobolev - slobodekii @xmath28 spaces , where @xmath8 is a closed smooth surface ( without boundary ) , which contains @xmath7 as a subsurface , @xmath29 . the bessel potential space @xmath30 is defined as a subset of the space of schwartz distributions @xmath31 endowedp with the norm ( see @xcite ) @xmath32 where @xmath33 is the bessel potential and @xmath34 , @xmath35 are the fourier transformations . for the definition of the sobolev - slobodekii space @xmath36 see @xcite . the space @xmath37 coincides with the trace space of @xmath38 on @xmath8 and is known that @xmath39 for @xmath40 , @xmath3 ( see @xcite ) . we use , as common , the notation @xmath41 and @xmath42 for the spaces @xmath43 and @xmath44 ( the case @xmath45 ) . the spaces @xmath46 and @xmath37 are defined by a partition of the unity @xmath47 subordinated to some covering @xmath48 of @xmath8 and local coordinate diffeomorphisms ( see @xcite for details ) @xmath49 the space @xmath50 is defined as the subspace of @xmath46 of those functions @xmath51 , which are supported in the closed sub - surface @xmath52 , whereas @xmath53 denotes the quotient space @xmath54 , and @xmath55 is the complemented sub - surface . for @xmath56 the space @xmath53 can be identified with the space of those distributions @xmath57 on @xmath58 which admit extensions @xmath59 , while @xmath53 is identified with the space @xmath60 , where @xmath61 denotes the restriction from @xmath8 to the sub - surface @xmath7 . it is worth noting that for an integer @xmath62 the sobolev spaces @xmath63 and @xmath64 coincide and the equivalent norm is defined with the help of the gnter s derivatives ( see @xcite ) : @xmath65^{\frac1p } , \quad\mbox { where } \quad { { \mathcal d}}^\alpha:={{\mathcal d}}^{\alpha_1}_1{{\mathcal d}}^{\alpha_2}_2{{\mathcal d}}^{\alpha_3}_3\ ] ] and the gnter s derivatives @xmath66 are defined in . let us also consider @xmath67 , a subspace of @xmath68 , orthogonal to @xmath69 @xmath70 consists of those distributions on @xmath8 , belonging to @xmath68 which have their supports just on @xmath20 and @xmath68 can be decomposed into the direct sum of subspaces : @xmath71 the space @xmath72 is non - empty ( see @xcite ) and excluding it from @xmath68 is needed to make bvps uniquelly solvable ( cf . @xcite and the next theorem [ t0.1 ] ) . the lax - milgram lemma applied to the bvp gives the following result . [ t0.1 ] the bvp has a unique solution in the classical weak setting : @xmath73 from theorem [ t0.1 ] we can not even conclude that a solution is continuous . if we can prove that there is a solution @xmath74 for some @xmath75 , we can enjoy even a hlder continuity of @xmath76 . it is very important to know maximal smoothness of a solution as , for example , while designing approximation methods . to this end we will investigate the solvability properties of the bvp in the following non - classical setting @xmath77 and find necessary and sufficient conditions of solvability . note , that the constraint @xmath2 is necessary to ensure the existence of the trace @xmath23 on the boundary . to formulate the main theorem of the present work we need the following definition . [ t0.2 ] the bvp , is fredholm if the homogeneous problem @xmath78 has a finite number of linearly independent solutions and only a finite number of orthogonality conditions on the data @xmath79 ensure the solvability of the bvp . we prove below the following theorem ( see the concluding part of 5 ) . [ t0.3 ] let @xmath3 , @xmath2 . the bvp is fredholm in the non - classical setting if and only if : @xmath80 in particular , the bvp has a unique solution @xmath76 in the non - classical setting if @xmath81 note , that conditions and are independent of the parameter @xmath82 . the proof of the foregoing theorem [ t0.3 ] in [ sect5 ] is based on the theorem [ t0.3a ] and theorem [ t0.4 ] . [ t0.3a ] let @xmath3 , @xmath2 . let @xmath83 and @xmath84 be some fixed extensions of the boundary data @xmath85 and @xmath86 ( non - classical formulation ) , initially defined on the parts of the boundary @xmath13 . a solution to the bvp is represented by the formula @xmath87 here @xmath88 , @xmath89 and @xmath90 are the newton s , double and single layer potentials , defined below @xmath91see @xmath92 and @xmath93 , @xmath94 in are solutions to the following system of pseudodifferential equations @xmath95 { \displaystyle}\frac12\psi_0+r_d{{\boldsymbol w}}^_{\gamma,0 } \psi_0-r_d{{\boldsymbol v}}_{\gamma,+1}\varphi_0=h_0\qquad & \text{on}\quad\gamma_d , \end{array}\right . \end{array}\\[2 mm ] \label{e0.7 } \begin{array}{c } \varphi_0\in{\widetilde}{{\mathbb{w}}}^{s-1/p}_p(\gamma_n),\quad \psi_0\in{\widetilde}{{\mathbb{w}}}^{s-1 - 1/p}_p(\gamma_d),\\[3 mm ] g_0\in{\mathbb{w}}^{s-1/p}_p(\gamma_n),\qquad h_0\in{\mathbb{w}}^{s-1 - 1/p}_p(\gamma_d ) , \end{array}\end{aligned}\ ] ] where @xmath96 and @xmath97 are given functions and the participating pseudodifferential operators are defined in 1 below . vice versa : if @xmath76 is a solution to the bvp , @xmath98 , @xmath99 and @xmath100 , @xmath101 are some fixed extensions of @xmath102 anf @xmath103 to @xmath20 , then @xmath104 , @xmath105 are solutions to the system . the system of boundary pseudodifferential equations has a unique pair of solutions @xmath106 and @xmath107 in the classical setting @xmath45 , @xmath108 . the proof of theorem [ t0.3a ] is exposed in [ sect1 ] . for the system we can remove the constraint @xmath2 and prove the following result for arbitrary @xmath109 . [ t0.4 ] let @xmath3 , @xmath110 . the system of boundary pseudodifferential equations is fredholm in the sobolev - slobodekii space setting @xmath111 g_0\in{\mathbb{w}}^r_p(\gamma_n),\qquad h_0\in{\mathbb{w}}^{r-1}_p(\gamma_d ) \end{array}\end{aligned}\ ] ] and also in the bessel potential space setting @xmath112 g_0\in{\mathbb{h}}^r_p(\gamma_n),\qquad h_0\in{\mathbb{h}}^{r-1}_p(\gamma_d ) \end{array}\end{aligned}\ ] ] if the following condition holds : @xmath113 in particular , the system has a unique solution in both settings and if : @xmath114 the proof of the foregoing theorem [ t0.4 ] in [ sect5 ] is based on the auxiliary theorem [ t0.5 ] . to formulate the theorem consider the following model system of boundary integral equations ( bies ) @xmath115 \psi(t ) + { { \boldsymbol k}}^1_{-1}{\varphi}(t)=h(t),\qquad & t\in{\mathbb{r}}^+,\end{array}\right.\\[2 mm ] & & \varphi,\psi\in{\widetilde}{{\mathbb{w}}}^{s-1 - 1/p}_p({\mathbb{r}}^+),\qquad g,\ ; h\in{\mathbb{w}}^{s-1 - 1/p}_p({\mathbb{r}}^+ ) , \nonumber\end{aligned}\ ] ] where @xmath116 is a mellin convolution operator with the kernel homogeneous of order @xmath117 ( see @xcite ) . [ t0.5 ] let @xmath3 , @xmath110 . + the system of boundary pseudodifferential equations is fredholm in the sobolev - slobodekii and bessel potential space settings if the system of boundary integral equations is locally invertible at @xmath118 in the sobolev - slobodekii @xmath119 and the bessel potential space @xmath120 settings , respectively . [ r0.7 ] theorem [ t0.5 ] is proved at the end of 1 . for the proof we apply a quasi - localization of the bvp with some model bvps on the half space ( see lemma [ l1.4 ] and lemma [ l1.5 ] ) . the constraint @xmath110 is due to this approach , since the boundary value problems are involved . in a forthcoming paper will be proved directly the local quasi - equivalence of the equation and the system at the points where the dirichlet and neumann boundary conditions collide and some simpler equations , which are uniquely solvable , at all other points . then the constraint @xmath110 can be dropped and replaced by @xmath109 . correspondingly , theorem [ t0.4 ] is also valid for all @xmath109 and the condition acquires the form @xmath121 a quasi - localization means `` freezing coefficients '' and `` rectifying '' underling contours and surfaces . for details of a quasi - localization we refer the reader to the papers @xcite and @xcite , where the quasi - localization is well described for singular integral operators and for bvps , respectively . we also refer to @xcite , where is exposed a short introduction to quasi - localization . in the present case under consideration we get 3 different model problems by localizing the mixed bvp to : inner points of @xmath7 . * inner points on the boundary @xmath122 and @xmath123 . * points of the boundary @xmath20 where different boundary conditions collide ( endpoints of @xmath123 and @xmath122 ) . the model bvps obtained by a quasi - localization , are well investigated in the first two cases and such model problems have unique solutions without additional constraints . in the third case we get a mixed bvp on the half plane for the laplace equation ( cf . the system is related to this model mixed problem just as bvp is related to the system ( cf . lemma [ l1.5 ] below ) . the investigation of the boundary integral equation system is based on recent results on mellin convolution equations with meromorphic kernels in bessel potential spaces ( see r. duduchava @xcite , r. duduchava and v. didenko @xcite ) . the symbol @xmath124 of the system is a continuous function on some infinite rectangle @xmath125 and is responsible for the fredholm property and the index of the system . this provides necessary and sufficient conditions for the fredholm property of which is then used to prove the solvability of the original bvp in the non - classical setting . a rigorous analysis of solvability of the above and similar problems with dirichlet , neumann , mixed and impedance boundary condition for the helmholtz and other other elliptic equations are very helpful for a general understanding of elliptic boundary value problems in conical domains ( see @xcite ) . in @xcite the authors suggest another approach to the investigation of the model mixed problem for the helmholtz equation : they write explicit formulae for a solution with two different methods . but the setting is classical only ( the case @xmath45 ) and the approach can not be applied to the non - classical setting . other known results are either very limited to special situations such as the rectangular case @xcite or apply rather sophisticated analytical methods @xcite , or are missing a precise setting of appropriate functional spaces ( see , e.g. , @xcite ) . for the historical survey and for further references we recommend @xcite . there is another approach , which can also be applied is the limiting absorption principle , which is based on variational formulation and lax - milgram lemma and its generalizations . such approach is presented , e.g. , in @xcite . but again , these results are for the classical setting . in 1960 s there was suggested to solve canonical diffraction problems in sobolev spaces , based on the recent development in pseudodifferential equations in domains with corners and , more generally , with a lipschitz boundary . it was popularized by e. meister @xcite , e. meister and f .- o . speck @xcite , w.l . wendland @xcite , a. ferreira dos santos @xcite and their collaborators in the 1980 s . also see the book of vasilev @xcite with a considerable list of references . the results are also restricted to the classical setting .	we investigate the mixed dirichlet - neumann boundary value problems for the laplace - beltrami equation on a smooth bounded surface with a smooth boundary in non - classical setting in the bessel potential space for , . to the initial bvp we apply a quasi - localization and obtain a model bvp for the laplacian . mce is ivestigated in both bessel potential and sobolev - slobodekii spaces . the symbol of the obtained system is written explicitly and is responsible for the fredholm properties and the index of the system . an explicit criterion for the unique solvability of the initial bvp in the non - classical setting is derived as well . * key words : * boundary value problem , mixed boundary conditions , potential method , fredholm criteria , symbol , banach algebra of operators , mellin convolution equation , meromorphic kernel . bessel potential space , besov space . * ams subject classifications : * primary 35j57 , secondary 45e10 , 47b35 * funding : * the research was supported by shota rustaveli national science foundation grants no . 13/14 and 31/39 . -5 mm	we investigate the mixed dirichlet - neumann boundary value problems for the laplace - beltrami equation on a smooth bounded surface with a smooth boundary in non - classical setting in the bessel potential space for , . to the initial bvp we apply a quasi - localization and obtain a model bvp for the laplacian . the model mixed bvp on the half plane is reduced to an equivalent system of mellin convolution equation ( mce ) in sobolev - slobodekii space ( potential method ) . mce is ivestigated in both bessel potential and sobolev - slobodekii spaces . the symbol of the obtained system is written explicitly and is responsible for the fredholm properties and the index of the system . an explicit criterion for the unique solvability of the initial bvp in the non - classical setting is derived as well . * key words : * boundary value problem , mixed boundary conditions , potential method , fredholm criteria , symbol , banach algebra of operators , mellin convolution equation , meromorphic kernel . bessel potential space , besov space . * ams subject classifications : * primary 35j57 , secondary 45e10 , 47b35 * funding : * the research was supported by shota rustaveli national science foundation grants no . 13/14 and 31/39 . -5 mm
hep-lat0103026	c	in this paper , we have studied the @xmath56 improvement of wilson quarks on anisotropic lattices . at the tree - level we find that a certain choice of the parameters , @xmath82 @xcite , is well - behaved in the region of practical interest for charmed hadrons , namely @xmath222 , while @xmath223 is small . on the other hand , with a different choice , @xmath85 @xcite , continuum behavior is reached only for @xmath224 . with this latter choice a non - relativistic interpretation @xcite is still possible , but a mass - independent renormalization , which was proposed in ref . @xcite , is obstructed . the choice @xmath82 also simplifies tree - level @xmath56 improvement . the action does not require separate temporal and spatial hopping parameters . the currents require mass - dependent matching factors , but no intrinsically dimension - four terms . we therefore have started to examine the behavior of this choice at the one - loop level . we have computed the one - loop contributions to the rest mass and to the matching factors of the vector and axial vector currents . the matching factors depend significantly on @xmath24 . a more critical observation is that they are well approximated by taylor expansions @xmath225 for @xmath226 and @xmath227@xmath228 . this region encompasses the one suitable for the charmed quark with currently available computer resources . there are several issues that remain to be studied . the first is to compute the one - loop corrections to the ratio of hopping parameters @xmath46 , the clover coefficients @xmath32 and @xmath47 , and dimension - four terms in the currents . the calculation of @xmath46 is especially difficult , because it requires the one - loop kinetic mass @xmath229}$ ] . as at the tree - level , it is crucial to compute the full mass dependence , so one can check whether low - order taylor expansions work well for @xmath222 . only with the full mass dependence can one check whether @xmath24 , which comes with the couplings in the action , and @xmath223 , which also comes from the on - shell condition , come together to form @xmath230 . if not , then one could proceed with a non - perturbative calculation of @xmath57 , @xmath58 , @xmath59 , @xmath60 , etc . a more practical problem is to define renormalized couplings . the scale - setting scheme of brodsky , lepage , and mackenzie ( blm ) is usually a good way to absorb the dominant part of two- and higher - order contributions @xcite . on an anisotropic lattice , it may make sense to define separate scales for temporal and spatial gluons . these results are of interest in any case : even if anisotropic lattice calculations require a non - relativistic interpretation for heavy quarks , anisotropy remains a useful tool for improving the signal - to - noise ratio . finally , after these problems are resolved , it will be important to combine the results with numerical simulation data to obtain the matrix elements relevant to experimental measurements of charmed hadrons .	we investigate the symanzik improvement of the wilson quark action on anisotropic lattices . taking first a general action with nearest - neighbor and clover interactions , we study the mass dependence of the ratio of the hopping parameters , the clover coefficients , and an improvement coefficient for heavy - light vector and axial vector currents . we show how tree - level improvement can be achieved . for	we investigate the symanzik improvement of the wilson quark action on anisotropic lattices . taking first a general action with nearest - neighbor and clover interactions , we study the mass dependence of the ratio of the hopping parameters , the clover coefficients , and an improvement coefficient for heavy - light vector and axial vector currents . we show how tree - level improvement can be achieved . for a particular choice of the spatial wilson coupling , the results simplify , and improvement is possible . ( here is the bare quark mass and the temporal lattice spacing . ) with this choice we calculate the renormalization factors of heavy - light bilinear operators at one - loop order of perturbation theory employing the standard plaquette gauge action .
1511.01450	i	the low - energy effective theory describing the dynamics of a collection of wrapped d - branes at small separations is given by quiver quantum mechanics @xcite . these d - branes form bound states and , depending on parameters , can either be well separated or on top of each other . when well separated , the theory is on the coulomb branch , parametrized by a macroscopic vev @xmath2 for the fields describing the separation between the branes . conversely , when the branes are on top of each other , the theory is on the higgs branch , parametrized by a large vev @xmath3 for the field representing the light stretched string mode between the branes . in this paper we will consider the simplest example of quiver quantum mechanics , describing the dynamics of a pair of d - branes with a single light stretched string mode between them . being a supersymmetric theory , the relative separation between the branes lives in a vector multiplet @xmath4 and the lightest stretched string mode lives in a chiral multiplet @xmath5 . these models have proven fruitful playgrounds for the study of supersymmetric black hole bound states at weak coupling @xcite . however , one obvious question remains unsolved : what is the structure of the bound state wavefunctions ? while supersymmetry allows us to make some statements about the structure of the ground states , the full ground state wavefunctions remain unknown @xcite . this is because , while simpler than the full schrdinger equation , the bps equations remain too difficult to solve analytically . the situation is worse for the excited states , where we have to abandon the crutch of supersymmetry altogether . it is our interest in this paper to construct the bps and excited states of this model . we will not be able to do so analytically , but there exist numerical methods to compute the eigenspectra of differential operators on a finite domain , see e.g. @xcite . using these techniques we numerically solve the schrdinger equation , plot bound state wavefunctions , and determine their energies . in our analysis , we find that the physics is governed by a dimensionless quantity @xmath1 defined in ( [ nu ] ) , which is inversely proportional to the fayet - iliopoulos parameter @xmath6 . the quantity @xmath1 dictates whether the higgs branch or the coulomb branch is the dominant description of the dynamics . in studying the wavefunctions and their dependence on @xmath1 , we uncover that the two branches never quite decouple and the wavefunction has nonzero support in both branches for any value of @xmath1 . since this model is supersymmetric , much work has gone into studying features of the ground states . for example , the ground state wavefunction was previously studied in a born - oppenheimer approximation @xcite , which involves splitting the hamiltonian @xmath7 into a vector part @xmath8 and a chiral part @xmath9 and putting the chiral degrees of freedom in the harmonic oscillator ground state of @xmath9 . one then ` integrates out ' the chiral multiplet and solves the effective supersymmetric quantum mechanics on the vector multiplet degrees of freedom . this approximation is self - consistent if we are on the coulomb branch , that is if the ground state is such that the branes are well separated , and is only valid for large values of @xmath10 . one easy way to see this is that integrating out the chiral degrees of freedom generates a nontrivial metric on the moduli space of the vector multiplet , which appears in the effective lagrangian as @xmath11 the moduli space metric is singular at the origin where the approximation breaks down . the structure of the ground state wavefunction near the origin has previously been out of reach , and herein we fill this gap . interestingly the effective quantum mechanics on the coulomb branch of this model has an enhanced symmetry , allowing for a full determination of the spectrum on the coulomb branch @xcite . in computing excited state wavefunctions we numerically compute the energy gap between the supersymmetric ground state and the first excited state as a function of @xmath1 . we verify that the gap approaches the analytically determined value on the coulomb branch as we increase @xmath1 . recently @xcite the witten index @xmath12 , twisted by a combination of global symmetries , has been computed for various quivers ; and for the model of interest in this paper , @xmath13 ( depending on the sign of the fayet - iliopoulos parameter @xmath6 ) . we indeed find a single bosonic ground state in the correct representation of the global symmetry , meaning our result can be thought of as the first _ in silico _ experimental confirmation of the mathematically predicted bps spectrum of the model . moreover , using the methods described in this note we have access to more than the count of bps states . this includes plots of the ground state and excited state wavefunctions , the gap with the first excited state as well as various field expectation values . the numerical methods we describe will hopefully make the study of the quantum nature of weakly coupled black hole bound states more tractable , and can potentially provide a useful experimental testing ground for other witten index calculations . the organization of this paper is as follows : in section [ setup ] we present the supercharges and symmetry generators of the theory . these fix the wavefunctions up to their dependence on radial variables . we also give a quick review of the stringy interpretation of this model . in section [ groundstatesec ] we provide the bps equations obeyed by the ground state wavefunction , suitably reduced via symmetries . we also plot numerical solutions ( bps and non - bps ) for the full schrdinger problem in the singlet sector of the bosonic symmetry group . we study the dependence of the bps and non - bps wavefunctions on @xmath1 . we conclude in section [ outlook ] . we have collected formulae in appendices [ sphereapp ] and [ wavefunceqs ] and review the born - oppenheimer approximate ground state wavefunction in appendix [ boapp ] .	we numerically construct the bps and non - bps wavefunctions of an quiver quantum mechanics with two abelian nodes and a single arrow . this model captures the dynamics of a pair of wrapped d - branes interacting via a single light string mode . we also numerically compute the energy gap between the ground state and the first excited states as a function of . an expression for the the gap , computed on the coulomb branch , matches nicely with our numerics at large but deviates at small where the higgs branch becomes the relevant description of the physics . in the appendix , we provide the schrdinger equations fully reduced via symmetries which , in principle , allow for the numerical determination of the entire spectrum at any point in moduli space . for the ground states , this numerical determination of the spectrum can be thought of as the first _ in silico _ check of various witten index calculations . mit - ctp-4731 susy in silico : numerical d - brane bound state spectroscopy tarek anous _ center for theoretical physics , massachusetts institute of technology , cambridge , ma 02139 , usa _	we numerically construct the bps and non - bps wavefunctions of an quiver quantum mechanics with two abelian nodes and a single arrow . this model captures the dynamics of a pair of wrapped d - branes interacting via a single light string mode . a dimensionless parameter , which is inversely proportional to the the fayet - iliopoulos parameter , controls whether the bulk of the wavefunctions are supported on the higgs branch or the coulomb branch . we demonstrate how the bps and excited states morph as is tuned . we also numerically compute the energy gap between the ground state and the first excited states as a function of . an expression for the the gap , computed on the coulomb branch , matches nicely with our numerics at large but deviates at small where the higgs branch becomes the relevant description of the physics . in the appendix , we provide the schrdinger equations fully reduced via symmetries which , in principle , allow for the numerical determination of the entire spectrum at any point in moduli space . for the ground states , this numerical determination of the spectrum can be thought of as the first _ in silico _ check of various witten index calculations . mit - ctp-4731 susy in silico : numerical d - brane bound state spectroscopy tarek anous _ center for theoretical physics , massachusetts institute of technology , cambridge , ma 02139 , usa _
0705.4319	i	hercules x-1 ( discovered by tananbaum et al . 1972 ) is one of the most frequently observed x - ray binary systems . the intermediate mass of the donor star , @xmath5 m@xmath6 , leads to a wealth of behavior seen in both low mass and high mass systems . although we suspect the mass flow is primarily through roche lobe overflow giving rise to an accretion disk , as in the low mass x - ray binaries ( lmxb ) , the variable p cygni profiles observed in uv lines suggest either a transient stellar wind or a stellar wind that is photoionized in some regions ( boroson , kallman , & vrtilek 2001 ) . there are theoretical grounds as well to expect that winds may arise in this system when x - rays from the neutron star heat the surface of the normal star or accretion disk ( arons 1973 ; davidson & ostriker 1973 ; basko et al . 1977 ; london , mccray , & auer 1981 ; begelman , mckee , & shields 1983 ; begelman & mckee 1983 ) . most lmxbs , including z - sources and atoll - sources , do not show persistent pulsations , perhaps because they have neutron stars with low magnetic fields . these sources thus lack an essential window into their kinematics . light travel - time delays in the 1.24 second her x-1 x - ray pulsation period determine that the neutron star is in a nearly circular 1.7 day orbit with semimajor axis a@xmath7 seconds . the orbital period is slowly lengthening from mass loss in the system ( deeter et al . 1991 ) . fortuitously , her x-1 has high orbital inclination ( @xmath8 degrees ) , allowing total x - ray eclipses to constrain the size of the donor star , and the high galactic latitude offers only small reddening , allowing the system to be observed at crucial uv and even euv wavelengths . the system s most mysterious variability is the 35-day x - ray high and low cycle ( giacconi et al . 1973 ) . for 811 days ( the `` main - on state '' ) of this cycle her x-1 emits x - rays with a @xmath9 erg s@xmath10 total x - ray luminosity . for a @xmath11 day cycle ( the `` short - on state '' ) , halfway through the 35 day cycle , her x-1 s output is several times lower . for the remaining portion of the 35 days , the off state , the observed x - ray flux is only several percent of that during the main - on state . the behavior of the optical flux and x - ray spectrum over the 35-day period shows that the 35-day variability is not isotropic . instead , the x - ray emission is merely obscured by a warped accretion disk whose shape precesses " globally throughout a 35-day period . the optical emission from the normal star varies with the 1.7 day binary orbit . its spectral type is variously classified as a through f , because x - rays from the neutron star heat the surface of the facing side of the roche lobe . the spectral type continues to change with the orbital period throughout the longer 35-day cycle , implying that x - rays continue to heat the surface of hz her . the transition between the off and main - on state is only a few hours , whereas the short - on state is entered into more gradually . this indicates that regions of the disk at different radii may obscure the central source , in which case the disk must precess globally with the same period . the variation in pulse shape with the long - term period is sometimes taken to imply that the innermost edge of the accretion disk precesses with the 35 day period , obscuring local regions on the neutron star ( scott , leahy , & wilson , 2000 ) . the physical cause of a 35-day global disk precessing disk warp , or a definitive relation between system parameters and disk precession period , remains unknown and is a major goal of investigations of the system . it has been proposed , but not confirmed , that reprocessed x - ray radiation pressure ( maloney & begelman 1997 ; wijers & pringle 1999 ) or an x - ray driven disk wind and corona ( meyer , meyer - hofmeister , 1984 ) could propagate the warped shape in the disk . similar " long - term periods have been observed in other x - ray binaries , including lmc x-4 . her x-1 serves as a prototype of this behavior . x - ray dips present another variability that has not been explained definitively . crosa & boynton ( 1980 ) showed that the dips recur every 1.65 days , near , but not at , the 1.62 day beat period between orbital and precessional periods . this was confirmed by long - term x - ray observations ( scott & leahy , 1999 ) . the dips are thought to be associated with the gas stream between the stars , but there is no consensus explanation for them or their period . as befits such a frequently observed , enigmatic , yet prototypical source , the methods of spectroscopy have been applied to the system at a wide range of wavelengths . these studies have borne fruit with determinations of the system s elemental abundances and the orbital motion of the normal star ( the neutron star s pulse delays indicate only the motion of one component of the binary ) . high resolution spectroscopy in the x - ray range using _ xmm _ ( jimenez - garate et al . 2002 ) shows a multitude of x - ray emission lines presumably from an accretion disk corona . the line ratios indicate that the gas is enhanced from cno processing from a massive progenitor . jimenez - garate et al . ( 2005 ) confirmed the cno enhancement by observations of more than two dozen emission lines originating in an accretion disk corona . model predictions of the disk corona s response to illumination by the central x - ray source are in reasonable agreement with the observed fluxes for low and moderate z elements ( o through s ) , but the fexxv , fexxvi lines are several times brighter than predicted ( jimenez - garate et al . 2005 ) . from observations of optical absorption lines ( reynolds et al . 1997 ) , and from optical pulsations that result from the x - rays from the neutron star periodically striking the surface of the normal star ( middleditch & nelson 1976 ) , we know that the normal star has a mass @xmath12 m@xmath6 and the neutron star has a mass 1.5@xmath13 m@xmath6 . the optical spectrum shows absorption lines from hz her , emission at the bowen blend near 4640 ( see schachter , filippenko , & kahn 1989 for a discussion of the formation of these lines ) , and emission from heii@xmath14 . still et al . ( 1997 ) performed doppler tomography on these optical emission lines but could not conclude that they arose in a symmetric accretion disk . the uv spectrum is crucial for an understanding of the accretion disk and the x - ray illuminated face of hz her . the continuum emission from both the illuminated star and the disk peaks in the uv and the disk contributes a greater fraction than at optical wavelengths ( cheng , vrtilek , & raymond 1995 ) . from models of the variable uv continuum as observed with the international ultraviolet explorer ( _ iue _ , vrtilek & cheng 1996 ) showed that a change in the accretion disk precession could explain an anomalously low period of x - ray emission . to study global accretion one should observe gas at ionization stages and temperatures resulting from x - ray illumination of the disk , and one would need to resolve doppler - shifted velocities that correspond to the orbital motion of the neutron star ( 160 km s@xmath10 ) , motion in the accretion disk ( expected to be @xmath15 km s@xmath10 at the edge of the disk ) , and the velocities expected in a disk or stellar wind ( @xmath16 km s@xmath10 ) . the strong uv resonance lines from nv , siiv , and civ , first seen with _ iue _ ( howarth & wilson 1983b ) , presumably result from photoionization of the accretion disk and hz her ( raymond 1993 , ko & kallman 1994 ) . these lines are much stronger than the strongest optical high ionization line , heii@xmath14 , both in absolute flux and equivalent width . observations with the faint object spectrograph ( fos ) aboard the hubble space telescope ( _ hst _ ) showed that these lines are still present at a few percent of maximum brightness during mid - eclipse when the disk and heated star should be entirely obscured ( anderson et al . the source of this emission may be an expanding wind . the goddard high resolution spectrograph ( ghrs ) on _ hst _ first resolved these emission lines at @xmath17 km s@xmath10 resolution ( boroson et al . , 1996 ) to discern variable broad and narrow emission components . the _ hst _ space telescope imaging spectrograph ( stis ) confirmed that the resonance lines have at least two components ( vrtilek et al . a broad component arises on the accretion disk while a narrow line component may be associated with hz her . prior to the stis observations , the accretion disk had only been observed as it contributed to the continuum light curve or obscured the central x - rays . during eclipse ingress and egress , the broad lines seen with stis behaved as expected for lines from an accretion disk rotating prograde with the orbital direction . the blue edge of the line was obscured first in eclipse ingress and appeared first in egress . observations with the far ultraviolet spectroscopic explorer ( _ fuse _ ) are complementary to the existing _ hst _ observations . long - term variability in the system makes it impossible to combine rigorously data from different epochs . analyzed separately , however , the _ fuse _ wavelength range of 900 - 1200 offers similar advantages and powerful consistency checks to analysis of the _ hst _ bandpass of 1200 - 1700 . both wavelength ranges have strong resonance lines that respond to x - ray photoionization . observations with the hopkins ultraviolet telescope ( _ hut _ ) showed that the ovi doublet has flux comparable to the nv doublet , the brightest near uv line ( boroson et al . 1997 ) . the resonance line doublets offer optical depth information through their doublet ratios , but if the lines are as broad as the doublet separation , it may be impossible to determine the individual contribution of each line where they overlap . the separations of civ@xmath18 , siiv@xmath19 , nv@xmath20 , ovi@xmath21 , svi@xmath22 correspond to doppler shifts of 500 , 1900 , 960 , 1650 , 3600 km s@xmath10 , respectively . the far uv lines ovi and svi compare favorably with the near uv lines ( i.e. have greater separation and are less likely to overlap ) , except for siiv , which suffers from confusion with an oiv blend near 1400 . for the present observations , we observed an entire 1.7 day binary orbit with _ fuse_. a major goal of this program was to apply the method of doppler tomography ( 7 ) , which has the advantage of diagnosing the accretion flow of different systems without bringing to bear more than a few assumptions . table 1 shows the measured physical parameters of the system and parameters we adopt for our models .	we observed an entire 1.7 day orbit of the x - ray binary hercules x-1 with the far ultraviolet spectroscopic explorer ( _ fuse _ ) . changes in the ovi line profiles through eclipse ingress and egress indicate a keplerian accretion disk spinning prograde with the orbit . these observations may show the first double - peaked accretion disk line profile to be seen in the hercules x-1 system . simulations show that the bright spot is too far offset from the roche lobe to result from uneven x - ray heating of its surface . the absence of disk signatures in the tomogram can be reproduced in simulations which include absorption from a stellar wind . = 1 based on observations made with the nasa - cnes - csa far ultraviolet spectroscopic explorer .	we observed an entire 1.7 day orbit of the x - ray binary hercules x-1 with the far ultraviolet spectroscopic explorer ( _ fuse _ ) . changes in the ovi line profiles through eclipse ingress and egress indicate a keplerian accretion disk spinning prograde with the orbit . these observations may show the first double - peaked accretion disk line profile to be seen in the hercules x-1 system . doppler tomograms of the emission lines show a bright spot offset from the roche lobe of the companion star hz her , but no obvious signs of the accretion disk . simulations show that the bright spot is too far offset from the roche lobe to result from uneven x - ray heating of its surface . the absence of disk signatures in the tomogram can be reproduced in simulations which include absorption from a stellar wind . we attempt to diagnose the state of the emitting gas from the ciii , ciii , and niii emission lines . the latter may be enhanced through bowen fluorescence . = 1 based on observations made with the nasa - cnes - csa far ultraviolet spectroscopic explorer . fuse is operated for nasa by the johns hopkins university under nasa contract nas5 - 32985
astro-ph0406272	i	the galactic x - ray transient h 1743@xmath0322 was classified as a black hole candidate by white & marshall ( 1984 ) based on its x - ray spectral characteristics . the source was discovered during its 19771978 outburst with _ heao-1 _ and _ ariel v _ ( doxsey et al . 1977 , kaluzienski & holt 1977 ) . the next convincing detection of h 1743@xmath0322 was made on 2003 march 21 with _ integral _ ( revnivtsev et al . 2003 ) and later with _ rxte _ ( markwardt & swank 2003a ) , earning the source the additional designations igr j17464@xmath03213 and xte j1746@xmath0322 . markwardt & swank ( 2003b ) pointed out that although the original _ _ detection reported two possible locations , it was very likely that the potentially new transient was actually h 1743@xmath0322 . following its 2003 re - activation in x - rays , the source was extensively monitored in optical , ir , and radio bands ( see , e.g. , rupen , mioduszewski , & dhawan 2003 ; steeghs et al . 2003 and ref . therein ) . two discoveries made during the 2003 outburst of h 1743@xmath0322 have provided additional evidence that this source harbors a black hole primary . first , homan et al . ( 2003 ) reported the detection of quasi - periodic oscillations ( qpos ) at 240 hz in the _ rxte _ x - ray flux . this frequency is typical of black hole candidates , and is tantalizingly close to the keplerian orbital frequency expected at the innermost stable circular orbit ( isco ) around a schwarzschild black hole ( @xmath6 ) . moreover , there is evidence for qpos at 160 hz , and therefore in the 2:3 ratio which has recently emerged in a few galactic black hole systems ( gro j1655@xmath040 : strohmayer 2001a , grs 1915@xmath7105 : strohmayer 2001b , xte j1550@xmath0564 : miller et al . 2001 , and possibly xte j1650@xmath0500 : homan et al . . the apparent 2:3 pairing may be evidence of a parametric epicyclic resonance in black hole accretion disks ( see , e.g. , abramowicz & kluzniak 2003 ) . however , there is evidence that black hole qpo pairs may drift out of a 2:3 ratio ( miller et al.2001 , remillard et al . 2002 ) , and the 2:3 ratio described by the resonance model for so - called khz qpos in neutron star systems is at odds with data ( miller 2003 ) . second , radio observations have revealed a jet in h 1743@xmath0322 , moving at @xmath8 ( rupen , mioduszewski , & dhawan 2004 ) . on the basis of this relativistic jet , h 1743@xmath0322 may be termed a `` microquasar '' . indeed , the x - ray spectroscopic results presented in this paper will further establish close similarities between h 1743@xmath0322 and microquasars like gro j1655@xmath040 and grs 1915@xmath7105 , in addition to their radio jet and x - ray timing similarities . although highly relativistic jets are not a unique black hole primary signature ( fender et al . 2004 ) , such jets are are more commonly observed in black hole systems than in neutron star systems . we observed h 1743@xmath0322 simultaneously with _ chandra _ and _ rxte _ on four occasions during the bright phase of its 2003 outburst , as part of our larger multi - wavelength black hole observing program . herein , we report the results of an analysis of the x - ray spectra resulting from these observations . most importantly , the _ chandra_/hetgs spectra reveal variable he - like fe xxv and h - like fe xxvi resonance absorption lines , which may be due to absorption in an outflow . variable , seyfert - like `` warm - absorber '' outflows have recently been detected in the x - ray spectra of the galactic black holes xte j1650@xmath0500 and gx 339@xmath04 ( miller et al.2004a , miller et al . we examine the absorption in h 1743@xmath0322 within the context of these recent results . the results of an analysis of the x - ray timing properties of the _ rxte _ observations will be reported in a companion paper ( homan et al.2004 ) . the results of radio observations made in partial support of this program will be reported in a separate paper by rupen et al . ( 2004 , in prep . ) , and results from optical and ir observations will be reported in steeghs et al . ( 2004 , in prep . )	chandra _ and _ rxte _ on four occasions . the _ chandra_/hetgs spectra reveal narrow , variable ( he - like ) fe xxv and ( h - like ) fe xxvi resonance absorption lines . in the first observation this wind may be a hot precursor to the seyfert - like , outflowing `` warm absorber '' we discuss these findings in the context of ionized fe absorption lines found in the spectra of other galactic sources , and connections to warm absorbers , winds , and jets in other accreting systems . [ firstpage ]	we observed the bright phase of the 2003 outburst of the galactic black hole candidate h 1743 in x - rays simultaneously with _ chandra _ and _ rxte _ on four occasions . the _ chandra_/hetgs spectra reveal narrow , variable ( he - like ) fe xxv and ( h - like ) fe xxvi resonance absorption lines . in the first observation , the fe xxvi line has a fwhm of km / s and a blue - shift of km / s , suggesting that the highly ionized medium is an outflow . moreover , the fe xxv line is observed to vary significantly on a timescale of a few hundred seconds in the first observation , which corresponds to the keplerian orbital period at approximately ( where ) . our models for the absorption geometry suggest that a combination of geometric effects and changing ionizing flux are required to account for the large changes in line flux observed between observations , and that the absorption likely occurs at a radius less than for a black hole . viable models for the absorption geometry include cyclic absorption due to an accretion disk structure , absorption in a clumpy outflowing disk wind , or possibly a combination of these two . if the wind in h 1743 has unity filling factor , the highest implied mass outflow rate is 20% of the eddington mass accretion rate . this wind may be a hot precursor to the seyfert - like , outflowing `` warm absorber '' geometries recently found in the galactic black holes gx 339 - 4 and xte j1650 . we discuss these findings in the context of ionized fe absorption lines found in the spectra of other galactic sources , and connections to warm absorbers , winds , and jets in other accreting systems . [ firstpage ]
astro-ph0406272	c	the high equivalent neutral hydrogen column density along the line of sight is consistent with a central galactic distance to h 1743@xmath0322 . for distances greater than @xmath853 kpc , the highest 0.510.0 kev unabsorbed flux observed ( see table 2 ) exceeds the eddington limit for a neutron star . moreover , the parameters obtained from broad - band spectral fits to h 1743@xmath0322 with the phenomenological mcd plus power - law model are typical for galactic black hole systems in bright phases ( for a review , see mcclintock & remillard 2003 , see also homan et al . 2001 ) . these facts and the presence of 240 hz qpos in h 1743@xmath0322 make it a near certainty that h 1743@xmath0322 harbors a black hole primary . however , the apparent absence of reflection features in the spectrum , even in phases with 1 ) a strong hard component , 2 ) a small inferred inner disk radius , and 3 ) high - frequency qpos , is at odds with the majority of galactic black holes . it is likely that the low reflection fraction obtained is due to a combination of astrophysical effects ( ionization and disk inclination ) and the limitations of our reflection modeling . zdziarski et al.(2003 ) have shown that when the disk is fully ionized , the reflected spectrum is nearly featureless , and might therefore be confused with a zero reflection scenario . high disk ionization tends to smooth - out reflection features ; the dips we have detected in the lightcurve of _ chandra _ observation 3 and in additional public _ rxte _ observations of h 1743@xmath0322 point to a system viewed at high inclination . at high inclinations , doppler shifts become very important , and tend to smear - out reflection features . the cdid reflection model we fit to _ rxte _ observation 2b indicates that the disk in h 1743@xmath0322 is likely highly ionized and seen at a high inclination . while these constraints are likely robust , it must be acknowledged that even the cdid model has limitations . it is implemented into xspec as a library of angle averaged spectra . finally , we note that if any reflection spectrum also passes through the hard x - ray emitting corona , which is likely if a corona hugs a disc viewed at high inclination , then the reflection component will be comptonized and much less detectable ( petrucci et al 2001 ) . it is possible , then , that the total reflection model the cdid model smeared with a line function ( for which inclination is a fit parameter ) does not address high inclinations correctly . were the combination of ionization and inclination effects more accurately described by our model , it is likely that a high reflection fraction would have been within errors . we have clearly detected variable , narrow fe xxv and fe xxvi resonance absorption lines in the spectra of h 1743@xmath0322 . in the recent past , similar absorption lines have been detected in the microquasars gro j1655@xmath040 ( ueda et al . 1998 ) , and grs 1915@xmath7105 ( kotani et al.2000 ) with _ asca _ , and in grs 1915@xmath7105 with _ ( lee et al . 2002 ) . unfortunately , each of these prior spectra suffered heavily from photon pile - up . the extraordinary sensitivity of the h 1743@xmath0322 spectra has allowed us to improve upon previous implications based on fe xxv / xxvi absorption lines in microquasars in two important ways : first , we have measured blue - shifts in the lines detected in observation 1 , providing direct evidence that the highly ionized absorbing geometry may be an outflow ( previously , outflows were only asserted ) . second , we have resolved the lines in two cases , and in other cases the lines are likely narrower than the instrumental resolution . the fwhm of the lines is vital for constraining the nature of the absorption . viable descriptions of the absorption geometry in h 1743@xmath0322 must be able to account for a number of our key findings , including : ( 1 ) the blue - shifts observed in the first _ observation , ( 2 ) the large line flux changes observed between observations ( in particular , the absence of absorption lines in the second _ chandra _ observation ) , and the stronger absorption seen in the dip observed during the third _ chandra _ observation , and ( 3 ) the absence of fe emission lines in the spectra , ( 4 ) the variability of the absorption lines in observation 1 on a timescale of a few hundred seconds , and ( 5 ) the absorption must occur at a radius smaller than the maximum radius at which our photoionization models suggest the lines may be produced . two geometries satisfy or partially satisfy most of these requirements : cyclic absorption in a disk structure resulting from the high inclination , and absorption in an ( potentially clumpy ) outflowing disk wind . the absence of fe emission lines in the _ chandra _ and _ rxte _ spectra suggests that the absorbing geometry is not spherical ( else , emission line photons would have scattered into our line of sight ) . indeed , modeling of the absorbers in gro j1655@xmath040 ( ueda et al.2004 ) and grs 1915@xmath7105 ( kotani et al . 2000 ) also suggested a cylindrical , perhaps pancake - like absorbing geometry . absorption in a disk structure perhaps a disk atmosphere is consistent with this constraint . however , this picture relies on relatively large covering and filling factors . the lack of emission lines in the spectra is also consistent with the absorption occurring in relatively dense clumps in a disk wind , with large covering factors but small filling factors . a clumpy wind is particularly appealing when one considers that at high mass accetion rates ( such as in the first _ chandra _ observation ) , our models for the absorber indicate that the wind would already be optically - thick at approximately @xmath86 . yet , we clearly see continuum spectral components consistent with viewing the innermost flow without significant obscuration . moreover , if qpos are tied to keplerian frequencies , the qpos detected ( homan et al . 2004 , in prep . ) indicate that emission from the innermost flow is either seen directly or scattered into our line of sight . a significant fraction of the absorption needs to occur in clumps with a high covering factor but small filling factor to be consistent with the observed continuum spectral properties and variability properties . the absence of absorption lines due to a combination of geometric effects and ionizing flux ( as implied by our photoionization models ) in the second _ chandra _ observation is easily explained by the clumpy outflow model . simply , a clump may not have intersected our line of sight to the central accretion observation within this observation . it is more difficult to explain the absence of absorption lines if the absorption occurs via cyclic absorption in a disk structure . the disk structure would have to be dampened or disappear in the second _ chandra _ observation . however , the ionizing flux is higher in this observation , and it has been shown that irradiation can induce warps in accretion disks ( see , e.g. , maloney , begelman , & pringle 1996 ) . to explain the enhanced absorption line fluxes measured within the dip in the third _ chandra _ observation , it is easy to envision a cool clump absorbing fe xxv more strongly than the hotter surrounding wind . alternatively , it is also possible that the dip observed is due to an unrelated geometric effect , and that the enhanced absorption line flux seen within the dip occurs because the wind along our line of sight is temporarily shielded and allowed to cool . if the absorption lines are instead due to absorption in a disk structure , a second warp or disk structure may need to be invoked to explain the dip itself . the variability of the fe xxv absorption line flux on timescales of a few hundred seconds in the first _ chandra _ observation can be explained by both models . indeed , this short timescale line variability is one of the most compelling arguments in favor of cyclic absorption in a disk structure . the period of the line variability broadly agrees with the keplerian orbital period at @xmath3 for a @xmath5 black hole . if h 1743@xmath0322 harbors a black hole with @xmath87 , then @xmath3 corresponds to @xmath88 cm , which is less than @xmath77 in observations 1 and 3 ( see table 5 ) . however , the observed variability can not be termed a qpo , and it is therefore less easily tied to a cyclic disk structure than if it qualified as a true qpo . if the absorption occurs in a disk structure , it would suggest that the variability itself is due to changes in the absorption in our line of sight . this is at odds with the fact that similar variability is observed in the absence of absorption lines in the second _ chandra _ observation . if the variability were due to absorption , the variability should be more pronounced at low energies ; in fact , the fractional rms of the peak at @xmath57 hz increases with higher energy ( homan et al . 2004b ; see figures 2 and 5 ) . although it is less exciting , absorption in a clumpy outflowing wind can likely account for the rapid line flux variability at least as well as cyclic absorption in a disk structure . simply , the gas ionization and recombination timescale is much faster than the variability timescale observed . if the variability is not due to a disk structure , but rather just due to fluctuations in the intensity of the central engine , an absorbing clump may be able to rapidly respond to the changing flux . finally , the blue - shifts observed in the first _ observation are more easily explained through an outflowing disk wind , than by absorption in the disk . the modest blue - shifts of the lines are a small fraction of the speed of light , and similar to the blue - shifted lines observed in gx 339@xmath04 and xte j1650@xmath0500 ( miller et al . 2004a ) , which are consistent with a disk wind . if the absorption is instead due to a cyclic disk structure , it is rather hard to explain the blue - shifts without significant fine - tuning . if the structure were a warp , its motion should be tangential to our line of sight , not into our line of sight . instead , the absorption might need to occur in a disk wind flowing outward along the disk , and further postulate that the wind density is modulated by a cyclic disk structure underlying the atmosphere . it has been shown that accretion disks may drive outflows with a significant component along the disk ( see , e.g. , murray & chiang 1997 , proga 2003 ) . on balance , absorption in an outflowing , clumpy wind appears to be the more compelling than absorption in a disk structure . both possibilities require a degree of fine - tuning to satisfy the observational constraints . a combination of these simple models may also be a viable description of the absorption geometry . the highly ionized outflow revealed in these _ chandra _ observations of h 1743@xmath0322 is very likely connected to the variable , outflowing , seyfert - like warm absorbers recently discovered in gx 339@xmath04 and xte j1650@xmath0500 ( miller et al . 2004a , miller et al.2004b ) . in those systems , the outflowing absorbers are consistent with disk winds or shell ejections . the absorbers in gx 339@xmath04 and xte j1650@xmath0500 are blue - shifted , and so clearly outflowing . in gx 339@xmath04 , he - like ne ix , mg xi , and o vii absorption lines were detected simultaneously with more strongly blue - shifted ne ii and ne iii lines , suggesting a `` clumpy '' outflow with regions of differing temperature and density . the fe xxv and fe xxvi lines in h 1743@xmath0322 also need to come from distinct regions , though the contrast needed is much less than for the wind observed in gx 339@xmath04 . the outflow observed in gx 339@xmath04 was likely detected at a lower fraction of the eddingtion mass accretion rate in that source ; its lower ionization can therefore be attributed to a lower central source flux . moreover , the outflow in gx 339@xmath04 implied an order of magnitude lower mass outflow rate than than the highest rate implied in h 1743@xmath0322 ( perhaps as high as 22% of the eddington inflow rate ) . the outflow in h 1743@xmath0322 may be clumpy , however , and have a low filling factor ; in that case , the outflow rate in h 1743@xmath0322 could be lower by a factor of @xmath89 , or more . it is plausible that the outflow in h 1743@xmath0322 is a hot , high @xmath90 precursor to the cooler , lower @xmath90 outflows observed in gx 339@xmath04 and xte j1650@xmath0500 ( miller et al . 2004a , 2004b ) . the mass outflow rate in the fourth _ chandra _ observation of h 1743@xmath0322 is far less than that in the first observation ( see table 5 ) , further indicating an evolution along the lines we suggest here . the outflows in these black hole systems are likely disk winds , and resemble the warm absorbers revealed in some seyfert galaxies ( see , e.g. , reynolds 1997 , elvis 2000 , morales & fabian 2002 ) . such absorption regions could be tied to rather equatorial disk outflows ( murray & chiang 1997 , proga 2003 ) , rather than to a highly collimated flow perpendicular to the disk . focused studies of galactic black hole winds in the future may enable us to learn about the evolution seyfert warm absorbers ; their evolution is difficult to study directly given the inherently longer timescales . it is worth addressing the possibility that a putative disk structure and the outflow are not merely coincident , but potentially causally related . for instance , a family of models has been discussed wherein jets or a wind can be launched vertically from a disk through a coupling between a spiral density wave in the disk and a rossby vortex ( tagger & pellat 1999 ; varniere , rodriguez , & tagger 2002 ; rodriguez , varniere , tagger , & durouchoux 2002 ) . it is possible , then , that the @xmath52s variations seen in h 1743@xmath0322 are due to a density structure which acts to drive jets close to the black hole , and that the same wave modulates a disk wind far from the black hole . it is not yet clear if such a mechanism could be at work in driving both jets and a disk wind , but if so , then the appearance of ionized fe absorption lines in strong jet sources like gro j1655@xmath040 , grs 1915@xmath7105 , and now h 1743@xmath0322 would be explained naturally . we note that using reduction methods exactly like those detailed for h 1743@xmath0322 , we have detected fe xxv and fe xxvi lines in a 60 ksec _ chandra_/hetgs spectrum of cygnus x-1 obtained on 3 march 2004 , when the source was in a canonical low / hard state ( miller et al.2004c , in prep . ) . cygnus x-1 is known to produce a compact , steady radio jet in this state ( stirling et al . highly ionized fe absorption lines have also been detected in the neutron star system gx 13@xmath71 ( sidoli et al . interestingly , gx 13@xmath71 is also a radio emitter in which a delay between its x - ray spectral hardness and radio brightness has been observed which is very similar to that seen in grs 1915@xmath7105 ( homan et al . 2004a ) , strongly suggesting a compact jet is also at work in this system . however , simultaneous radio observations of h 1743@xmath0322 with the vla / vlba reveal that the radio source was quite strong during the first and second _ chandra _ observations nearly 10 mjy at ghz frequencies ) but only 2 mjy during the third observation , and less than 1 mjy during the fourth observation ( rupen et al . 2004 , in prep . ) . thus , strong radio activity ( indicative of a jet ) is seen during the second _ chandra _ observation ( where absorption lines are not observed ) , and absorption lines are clearly observed in the third and fourth _ chandra _ observations when the radio flux was low . at minimum , this suggests that if jets and ionized absorption are causally related , they are not related in a simple way . both may merely be the effect of a strongly active corona , for instance . moreover , the detection of highly ionized fe absorption lines in high inclination neutron star binaries may signify that it is unlikely that ionized absorption lines are tied to jet production through a mechanism like aei . similar lines have also been seen in the persistent emission of the ( edge - on ) dipping neutron star binaries x 1254@xmath0690 ( boirin & parmar 2003 ) , x 1624@xmath0490 ( parmar et al.2002 ) , mxb 1658@xmath029 ( sidoli et al . 2001 ) and 4u 1916@xmath0053 ( boirin et al . 2004 ) . in contrast to the absorption lines in the black hole systems h 1743@xmath0322 , gx 339@xmath04 , and xte j1650@xmath0500 , the absorption lines in these edge - on neutron star binaries are not significantly blue - shifted . although the appearance of lines in both black hole and neutron star systems suggests a related physical origin , the lack of blue - shifts in the lines seen in neutron stars may hint at a different physical picture . without significant blue - shifts , it is difficult to clearly tie the lines to an outflow . the lines may not be due to absorption in an outflow , but might be due to absorption in ambient gas within the system . the absorption lines in mxb 1658@xmath029 , for instance , are not observed to vary with orbital phase or even during dipping events ( sidoli et al . 2001 ) , which suggests that the absorbing gas is not as close to the compact object as the absorbing gas in black hole systems . + we wish to thank cxc director harvey tananbaum and the cxc staff , and jean swank and the _ rxte _ staff , for making these too observations . we thank john houck for assistance with isis . jmm acknowledges helpful discussions with mike nowak , david huenemoerder , aneta siemiginowska , rob fender , herman marshall , and patrick wojdowski . jmm gratefully acknowledges support from the nsf through its astronomy and astrophysics postdoctoral fellowship program . whgl and jh gratefully acknowledge support from nasa . ds acknowledges support from the sao clay fellowship . this research has made use of the data and resources obtained through the heasarc on - line service , provided by nasa - gsfc . houck , j. c. , & denicola , l. a. , 2000 , astronomical data analysis software and systems ix , in asp conference proceedings , vol . 216 , eds . n. manset , c. veillet , & d. crabtree ; isis is available at http://space.mit.edu/cxc/isis lll instrument & start time & net exposure ( ksec ) + cxo / acis@xmath7hetgs & 2003 - 05 - 01t21:41:03 & 48.8 + rxte / pca 1a & 2003 - 05 - 01t17:00:32 & 25.2 + rxte / pca 1b & 2003 - 05 - 02t00:02:24 & 0.8 + rxte / pca 1c & 2003 - 05 - 02t00:54:08 & 3.3 + cxo / acis@xmath7hetgs & 2003 - 05 - 28t04:09:21 & 45.5 + rxte / pca 2a & 2003 - 05 - 28t05:28:48 & 1.5 + rxte / pca 2b & 2003 - 05 - 28t06:44:16 & 16.1 + rxte / pca 2c & 2003 - 05 - 28t14:28:32 & 5.6 + cxo / acis@xmath7hetgs & 2003 - 06 - 23t15:56:10 & 50.0 + rxte / pca 3 & 2003 - 06 - 23t17:05:20 & 13.3 + cxo / acis@xmath7hetgs & 2003 - 07 - 30t15:57:58 & 50.2 + rxte / pca 4a & 2003 - 07 - 30t19:48:48 & 0.6 + rxte / pca 4b & 2003 - 07 - 30t21:22:40 & 0.6 + rxte / pca 4c & 2003 - 07:31t00:32:48 & 0.6 + lllllllll observation & 1a & 1b & 1c & 2a & 2b & 2c & 3 & 4 + @xmath91 & @xmath92 & @xmath92 & @xmath92 & @xmath92 & @xmath92 & @xmath92 & @xmath92 & @xmath92 + @xmath93 ( kev ) & @xmath94 & @xmath94 & @xmath95 & @xmath95 & @xmath96 & @xmath97 & @xmath98 & @xmath99 + @xmath100 & @xmath101 & @xmath102 & @xmath103 & @xmath104 & @xmath105 & @xmath106 & @xmath107 & @xmath108 + @xmath109 & @xmath110 & @xmath111 & @xmath112 & @xmath113 & @xmath114 & @xmath115 & @xmath116 & @xmath117 + @xmath118 & @xmath119 & @xmath120 & @xmath121 & @xmath122 & @xmath123 & @xmath124 & @xmath125 & @xmath126 + @xmath127 & @xmath128 & @xmath129 & @xmath130 & @xmath131 & @xmath132 & @xmath133 & @xmath134 & @xmath135 + @xmath136 ( 3 - 100 ) & @xmath137 & @xmath137 & @xmath137 & @xmath138 & @xmath139 & @xmath140 & @xmath141 & @xmath142 + @xmath143 ( 3 - 100 ) @xmath144 & @xmath145 & @xmath146 & @xmath147 & @xmath148 & @xmath149 & @xmath150 & @xmath151 & @xmath152 + @xmath153 & @xmath154 & @xmath155 & @xmath156 & @xmath157 & @xmath158 & @xmath159 & @xmath160 & @xmath161 + @xmath136 ( 0.5 - 10 ) & @xmath162 & @xmath163 & @xmath164 & @xmath165 & @xmath166 & @xmath167 & @xmath168 & @xmath169 + @xmath143 ( 0.5 - 10 ) @xmath144 & @xmath170 & @xmath171 & @xmath172 & @xmath156 & @xmath173 & @xmath174 & @xmath175 & @xmath161 + fe k@xmath9 ( fwhm@xmath1850 kev ) ( ev ) & @xmath186 & @xmath186 & @xmath187 & @xmath188 & @xmath189 & @xmath190 & @xmath190 & @xmath191 + fe k@xmath9 ( fwhm@xmath1852 kev ) ( ev ) & @xmath191 & @xmath188 & @xmath188 & @xmath192 & @xmath193 & @xmath194 & @xmath195 & @xmath189 + lllllllllllll obs . & & theor . & meas . & shift & & flux & w & n@xmath196 & n@xmath197 + & & ( ) & ( ) & ( km / s ) & ( @xmath198 ) & ( km / s ) & ( @xmath198 ph/@xmath199/s ) & ( m ) & ( @xmath200 ) & ( @xmath201 ) + 1 & & 1.850 & 1.848(1 ) & @xmath202 & @xmath203 & @xmath204 & @xmath205 & @xmath206 & @xmath207 & @xmath208 + 1 & & 1.780 & 1.776(1 ) & @xmath209 & @xmath210 & @xmath1 & @xmath211 & @xmath212 & @xmath213 & @xmath214 + 3 & & 1.850 & 1.851(2 ) & @xmath221 & @xmath222 & @xmath223 & @xmath224 & @xmath225 & @xmath226 & @xmath227 + 3 & & 1.780 & 1.778(1 ) & @xmath228 & @xmath229 & @xmath230 & @xmath231 & @xmath232 & @xmath233 & @xmath234 + 4 & & 1.850 & 1.850(1 ) & @xmath235 & @xmath236 & @xmath237 & @xmath238 & @xmath239 & @xmath240 & @xmath241 + 4 & & 1.780 & 1.781(1 ) & @xmath242 & @xmath243 & @xmath244 & @xmath245 & @xmath246 & @xmath247 & @xmath119 + lllllllllllll obs . & & theor . & meas . & shift & & flux & w & n@xmath196 & n@xmath197 + & & ( ) & ( ) & ( km / s ) & ( @xmath198 ) & ( km / s ) & ( @xmath198 ph/@xmath199/s ) & ( m ) & ( @xmath200 ) & ( @xmath201 ) + 1 ( @xmath248mean ) & & 1.850 & & & @xmath249 & @xmath250 & @xmath251 & @xmath252 & @xmath220 & @xmath217 + 1 ( @xmath253mean ) & & 1.850 & 1.848(1 ) & @xmath202 & @xmath249 & @xmath250 & @xmath254 & @xmath148 & @xmath255 & @xmath256 + 1 ( @xmath248mean ) & & 1.780 & 1.776(1 ) & @xmath209 & @xmath257 & @xmath258 & @xmath134 & @xmath259 & @xmath260 & @xmath151 + 1 ( @xmath253mean ) & & 1.780 & 1.776(1 ) & @xmath209 & @xmath261 & @xmath262 & @xmath128 & @xmath156 & @xmath172 & @xmath263 + 1 ( mean@xmath75 c / s ) & & 1.850 & & & @xmath249 & @xmath250 & @xmath220 & @xmath264 & @xmath265 & @xmath218 + 1 ( mean@xmath05 c / s ) & & 1.850 & 1.849(1 ) & @xmath266 & @xmath249 & @xmath250 & @xmath234 & @xmath133 & @xmath267 & @xmath268 + 1 ( mean@xmath75 c / s ) & & 1.780 & 1.775(1 ) & @xmath269 & @xmath257 & @xmath258 & @xmath128 & @xmath270 & @xmath271 & @xmath145 + 1 ( mean@xmath05 c / s ) & & 1.780 & 1.777(1 ) & @xmath272 & @xmath273 & @xmath274 & @xmath206 & @xmath156 & @xmath172 & @xmath263 + 3 ( norm . ) & & 1.850 & & & @xmath249 & @xmath250 & @xmath218 & @xmath275 & @xmath251 & @xmath217 + 3 ( dip ) & & 1.850 & 1.850(1 ) & @xmath235 & @xmath249 & @xmath250 & @xmath276 & @xmath277 & @xmath206 & @xmath278 + 3 ( norm . ) & & 1.780 & 1.777(1 ) & @xmath272 & @xmath249 & @xmath250 & @xmath279 & @xmath280 & @xmath281 & @xmath226 + 3 ( dip ) & & 1.780 & 1.778(1 ) & @xmath228 & @xmath249 & @xmath250 & @xmath254 & @xmath282 & @xmath283 & @xmath145 + c r r r r r r r r r observation & @xmath284 & @xmath285 & @xmath286 & @xmath287 & @xmath288 + 1 & @xmath289 & @xmath290 & @xmath291 & @xmath292 & @xmath293 + 2 & @xmath294 & & @xmath295 & @xmath296 & + 3 & @xmath297 & @xmath298 & @xmath299 & @xmath300 & @xmath301 + 4 & @xmath302 & @xmath303 & @xmath304 & @xmath305 & @xmath306 +	, the fe xxvi line has a fwhm of km / s and a blue - shift of km / s , suggesting that the highly ionized medium is an outflow . moreover , the fe xxv line is observed to vary significantly on a timescale of a few hundred seconds in the first observation , which corresponds to the keplerian orbital period at approximately ( where ) . our models for the absorption geometry suggest that a combination of geometric effects and changing ionizing flux are required to account for the large changes in line flux observed between observations , and that the absorption likely occurs at a radius less than for a black hole . viable models for the absorption geometry include cyclic absorption due to an accretion disk structure , absorption in a clumpy outflowing disk wind , or possibly a combination of these two . geometries recently found in the galactic black holes gx 339 - 4 and xte j1650 .	we observed the bright phase of the 2003 outburst of the galactic black hole candidate h 1743 in x - rays simultaneously with _ chandra _ and _ rxte _ on four occasions . the _ chandra_/hetgs spectra reveal narrow , variable ( he - like ) fe xxv and ( h - like ) fe xxvi resonance absorption lines . in the first observation , the fe xxvi line has a fwhm of km / s and a blue - shift of km / s , suggesting that the highly ionized medium is an outflow . moreover , the fe xxv line is observed to vary significantly on a timescale of a few hundred seconds in the first observation , which corresponds to the keplerian orbital period at approximately ( where ) . our models for the absorption geometry suggest that a combination of geometric effects and changing ionizing flux are required to account for the large changes in line flux observed between observations , and that the absorption likely occurs at a radius less than for a black hole . viable models for the absorption geometry include cyclic absorption due to an accretion disk structure , absorption in a clumpy outflowing disk wind , or possibly a combination of these two . if the wind in h 1743 has unity filling factor , the highest implied mass outflow rate is 20% of the eddington mass accretion rate . this wind may be a hot precursor to the seyfert - like , outflowing `` warm absorber '' geometries recently found in the galactic black holes gx 339 - 4 and xte j1650 . we discuss these findings in the context of ionized fe absorption lines found in the spectra of other galactic sources , and connections to warm absorbers , winds , and jets in other accreting systems . [ firstpage ]
1102.3360	i	in the 18th century , euler considered the problem of optimizing functionals depending not only on some unknown function @xmath0 and some derivative of @xmath0 , but also on an antiderivative of @xmath0 ( see @xcite ) . similar problems have been recently investigated in @xcite , where lagrangians containing higher - order derivatives and optimal control problems are considered . more generally , it has been shown that the results of @xcite hold on an arbitrary time scale @xcite . here we study such problems within the framework of fractional calculus . roughly speaking , a fractional calculus defines integrals and derivatives of non - integer order . let @xmath1 be a real number and @xmath2 be such that @xmath3 . here we follow @xcite and @xcite . let @xmath4\to\mathbb{r}$ ] be piecewise continuous on @xmath5 and integrable on @xmath6 $ ] . the left and right riemann liouville fractional integrals of @xmath7 of order @xmath8 are defined respectively by @xmath9 here @xmath10 is the well - known gamma function . then the left @xmath11 and right @xmath12 riemann liouville fractional derivatives of @xmath7 of order @xmath8 are defined ( if they exist ) as @xmath13 and @xmath14 the fractional derivatives and have one disadvantage when modeling real world phenomena : the fractional derivative of a constant is not zero . to eliminate this problem , one often considers fractional derivatives in the sense of caputo . let @xmath7 belong to the space @xmath15;\mathbb{r})$ ] of absolutely continuous functions . the left and right caputo fractional derivatives of @xmath7 of order @xmath8 are defined respectively by @xmath16 and @xmath17 these fractional integrals and derivatives define a rich calculus . for details see the books @xcite . here we just recall a useful property for our purposes : integration by parts . for fractional integrals , @xmath18 ( see , , ( * ? ? ? * lemma 2.7 ) ) , and for caputo fractional derivatives @xmath19_a^b\ ] ] ( see , , ( * ? ? ? * eq . ( 16 ) ) ) . in particular , for @xmath20 one has @xmath21_a^b.\ ] ] when @xmath22 , @xmath23 , @xmath24 , @xmath25 is the identity operator , and gives the classical formula of integration by parts . the fractional calculus of variations concerns finding extremizers for variational functionals depending on fractional derivatives instead of integer ones . the theory started in 1996 with the work of riewe , in order to better describe non - conservative systems in mechanics @xcite . the subject is now under strong development due to its many applications in physics and engineering , providing more accurate models of physical phenomena ( see , , @xcite ) . with respect to results on fractional variational calculus via caputo operators , we refer the reader to @xcite and references therein . our main contribution is an extension of the results presented in @xcite by considering lagrangians containing an antiderivative , that in turn depend on the unknown function , a fractional integral , and a caputo fractional derivative ( section [ sec : fundprob ] ) . transversality conditions are studied in section [ sec : natbound ] , where the variational functional @xmath26 depends also on the terminal time @xmath27 , @xmath28 , and where we obtain conditions for a pair @xmath29 to be an optimal solution to the problem . in section [ sec : isoprob ] we consider isoperimetric problems with integral constraints of the same type as the cost functionals considered in section [ sec : fundprob ] . fractional problems with holonomic constraints are considered in section [ sec : holonomic ] . the situation when the lagrangian depends on higher order caputo derivatives , , it depends on @xmath30 for @xmath31 , @xmath32 , is studied in section [ sec : higher ] , while section [ sec : fracopt ] considers fractional lagrange problems and the hamiltonian approach . in section [ sec : sufconditions ] we obtain sufficient conditions of optimization under suitable convexity assumptions on the lagrangian . we end with section [ sec : numsim ] , discussing a numerical scheme for solving the proposed fractional variational problems . the idea is to approximate fractional problems by classical ones . numerical results for two illustrative examples are described in detail .	isoperimetric problems , problems with holonomic constraints and depending on higher - order caputo derivatives , as well as fractional lagrange problems , are considered . 49k05 , 49s05 , 26a33 , 34a08 . calculus of variations , fractional calculus , caputo derivatives , fractional necessary optimality equations .	we obtain necessary optimality conditions for variational problems with a lagrangian depending on a caputo fractional derivative , a fractional and an indefinite integral . main results give fractional euler lagrange type equations and natural boundary conditions , which provide a generalization of previous results found in the literature . isoperimetric problems , problems with holonomic constraints and depending on higher - order caputo derivatives , as well as fractional lagrange problems , are considered . 49k05 , 49s05 , 26a33 , 34a08 . calculus of variations , fractional calculus , caputo derivatives , fractional necessary optimality equations .
1307.6388	i	we have examined the stability properties of a relativistic magnetized cylindrical flow in the approximation of zero thermal pressure , neglecting also the effects of rotation and focusing only on the @xmath0 mode . in this configuration we have two kinds of instability that may be present : kelvin - helmholtz and current driven . the instability behavior depends of course on the chosen equilibrium configuration and this is somewhat arbitrary since we have no direct information on the magnetic field structure , although some indications are provided by the acceleration models ( see e.g. * ? ? ? nevertheless , the general outcome and the properties of the solutions obtained for a particular configuration , such as the one we adopted here , can be considered valid for a more general class of equilibria . our results can then be considered representative of an equilibrium configuration characterized by a distribution of current concentrated in the jet , with the return current assumed to be mainly found at very large distances . we can summarize our results by considering the behavior of the system for different values of the ratio between matter and magnetic energy densities . for matter dominated flows , the dominant instability is kh and the wavenumber corresponding to the maximum growth rate as well as the growth rate itself scale both as @xmath170 . somewhat above equipartion khi reaches its maximum growth rate and then it becomes rapidly stabilized . below this stabilization limit the dominant instability becomes cdi the dependence of the khi on the value of the pitch is relatively weak and only for the smallest value of the axial pitch ( @xmath61 ) , in the relativistic case , we observe a displacement of the stability limit towards lower values of @xmath108 and a merging with cdi . cdi are therefore prevailing for flows in equipartition or magnetically dominated and the dependence on @xmath108 in these regimes is quite weak . the wavenumber corresponding to the maximum growth rate scale as @xmath117 , the growth rate itself increases with decreasing @xmath61 . and the modes have a resonant character with a peak in the eigenfunction at the radial position where @xmath188 . at low jet velocity , our equilibrium has no return current inside the domain , while at relativistic velocities we have a small portion of the return current corresponding to the velocity shear region . the corresponding steepening of the pitch profiles induces a stabilization of the modes for which the resonance condition corresponds to radial positions where the return current is found . we then observe a splitting of the cdi in two branches , one at high wavenumbers ( the inner mode ) characterized by an eigenfunction with a resonant peak in the inner radial part of the flow , and one at smaller wavenumbers ( the outer mode ) for which the resonant peak is outside the jet region . which of the two branches is dominant depends on the width of the current distribution and on the lorentz factor of the flow . an increase in the current concentration ( small @xmath45 ) favors the growth of the inner mode , while an increase in @xmath73 enhances the development of the outer mode . the different behavior in the explored parameter ranges may have crucial implications for the nonlinear stages as distinct types of instability may evolve differently . this study is therefore an essential first step for the interpretation of the results of numerical simulations that will be presented in a following paper and for their comparison with astrophysical data .	we perform a linear analysis of the stability of a magnetized relativistic non - rotating cylindrical flow in the aproximation of zero thermal pressure , considering only the mode . the current driven mode is splitted in two branches , the branch at high wavenumbers is characterized by the eigenfunction concentrated in the jet core , the branch at low wavenumbers is instead characterized by the eigenfunction that extends outside the jet velocity shear region .	we perform a linear analysis of the stability of a magnetized relativistic non - rotating cylindrical flow in the aproximation of zero thermal pressure , considering only the mode . we find that there are two modes of instability : kelvin - helmholtz and current driven . the kelvin - helmholtz mode is found at low magnetizations and its growth rate depends very weakly on the pitch parameter . the current driven modes are found at high magnetizations and the value of the growth rate and the wavenumber of the maximum increase as we decrease the pitch parameter . in the relativistic regime the current driven mode is splitted in two branches , the branch at high wavenumbers is characterized by the eigenfunction concentrated in the jet core , the branch at low wavenumbers is instead characterized by the eigenfunction that extends outside the jet velocity shear region . [ firstpage ] galaxies : jets , mhd , instabilities , relativistic processes
astro-ph0512272	i	one of the great unsolved problems of planet formation is how to form planetesimals , the kilometer - sized precursors of real planets @xcite . at this size solid bodies in a protoplanetary disk can attract each other through gravitational two - body encounters , whereas gravity is insignificant between smaller bodies . starting from micrometer - sized dust grains , the initial growth is caused by the random brownian motion of the grains ( e.g. * ? ? ? * ; * ? ? ? * see @xcite for a review ) . the vertical component of the gravity from the central object causes the gas in the disk to be stratified with a higher pressure around the mid - plane . even though the dust grains do not feel this pressure gradient , the strong frictional coupling with the gas prevents small grains from having any significant vertical motion relative to the gas however , once the grains have coagulated to form pebbles with sizes of a few centimeters , the solids are no longer completely coupled to the gas motion . they are thus free to fall , or sediment , towards the mid - plane of the disk . the increase in dust density opens a promising way of forming planetesimals by increasing the local dust density around the mid - plane of the disk to values high enough for gravitational fragmentation of the dust layer @xcite . there are however two major unresolved problems with the gravitational fragmentation scenario . any global turbulence in the disk causes the dust grains to diffuse away from the mid - plane , and thus the dust density is kept at values that are too low for fragmentation . a turbulent @xmath0-value of @xmath1 is generally enough to prevent efficient sedimentation towards the mid - plane @xcite , whereas the @xmath0-value due to magnetorotational turbulence @xcite is from a few times @xmath2 ( found in local box simulations with no imposed magnetic field ) to 0.1 and higher ( in global disk simulations ) . the presence of a magnetically dead zone around the disk mid - plane @xcite may not mean that there is no turbulence in the mid - plane , as other instabilities may set in and produce significant turbulent motion @xcite . the magnetically active surface layers of the disk can even induce enough turbulent motion in the mid - plane to possibly prevent efficient sedimentation of dust @xcite . the presence of a dead zone may actually _ in itself _ be a source of turbulence . the sudden fall of the accretion rate can lead to a pile up of mass in the dead zone , possibly igniting the magnetorotational instability in bursts @xcite or a rossby wave instability @xcite . the second major problem with the gravitational fragmentation scenario is that even in the absence of global disk turbulence , the dust sedimentation may in itself destabilize the disk . protoplanetary disks have a radial pressure gradient , because the temperature and the density fall with increasing radial distance from the central object , so the gas rotates at a speed that is slightly below the keplerian value . the dust grains feel only the gravity and want to rotate purely keplerian . close to the equatorial plane of the disk , where the sedimentation of dust has increased the dust - to - gas ratio to unity or higher , the gas is forced by the dust to orbit at a higher speed than far away from the mid - plane where the rotation is still sub - keplerian . thus there is a vertical dependence of the gas rotation velocity . such shear flow can be unstable to the kelvin - helmholtz instability ( khi ) , depending on the stabilizing effect of vertical gravity and density stratification . a necessary criterion for the khi is that the energy required to lift a fluid parcel of gas and dust vertically upwards by an infinitesimal distance is available in the relative vertical motion between infinitesimally close parcels @xcite . the turbulent motions resulting from the khi are strong enough to puff up the dust layer and prevent the formation of an infinitesimally thin dust sheet around the mid - plane of the disk @xcite . modifications to the gravitational fragmentation scenario have been suggested to overcome the problem of kelvin - helmholtz turbulence . @xcite ( 1998 , hereafter referred to as s98 ) found that if the mid - plane of the disk is in a state of constant richardson number , as expected for small grains whose settling time is long compared to the growth rate of the khi , then an increase in the global dust - to - gas ratio can lead to the formation of a high density dust cusp very close to the mid - plane of the disk , reaching potentially a dust - to - gas ratio of 100 already at a global dust - to - gas ratio that is 10 times the canonical interstellar value of @xmath3 . the appearance of a superdense dust cusp in the very mid - plane has been interpreted by @xcite as an inability of the gas ( or of the khi ) to move more mass than its own away from the mid - plane . as a source of an increased value of the global dust - to - gas ratio , @xcite suggest that the dust grains falling radially inwards through the disk pile up in the inner disk . a slowly growing radial self - gravity mode in the dust density has also been suggested as the source of an increased dust - to - gas ratio at certain radial locations @xcite . trapping dust boulders in a turbulent flow is a mechanism for avoiding the problem of self - induced kelvin - helmholtz turbulence altogether @xcite . if the dust can undergo a gravitational fragmentation locally , because the boulders are trapped in features of the turbulent gas flow such as vortices or high - pressure regions , then there is no need for an extremely dense dust layer around the mid - plane . @xcite found that meter - sized dust boulders are temporarily trapped in regions of slight gas overdensity in magnetorotational turbulence , increasing the dust - to - gas ratio locally by up to two orders of magnitude . they estimate that the dust in such regions should have time to undergo gravitational fragmentation before the high - pressure regions dissolve again . @xcite , on the other hand , find that vortices can even form in magnetorotationally turbulent disks , keeping dust boulders trapped for hundreds of disk rotation periods . the khi can not operate inside a vortex because there is no radial pressure gradient , and thus no vertical shear , in the center of the vortex @xcite . from a numerical side it has been shown many times that a pure shear flow , i.e. one that is not explicitly supported by any forces , is unstable , both with magnetic fields @xcite and without @xcite . but the key point here is that the vertical shear formed in a protoplanetary disk is due to the sedimentation of dust , and that the shear is able to regenerate as the dust falls down again , thus keeping the flow unstable to khi . the description of the full non - linear outcome of such a system requires numerical simulations that include dust that can move relative to the gas . linear stability analysis of dust - induced shear flows in protoplanetary disks have been performed for simplified physical conditions @xcite , but also with coriolis forces and keplerian shear included @xcite . recently @xcite ( 2005 , hereafter referred to as go05 ) took an approach to include the dust into their numerical simulations of the kelvin - helmholtz instability by having the dust grains so extremely well - coupled to the gas that they always move with the instantaneous velocity of the gas . this is indeed a valid description of the dynamics of tiny dust grains . however , the strong coupling to the gas does not allow the dust grains to fall back towards the mid - plane . thus the saturated state of the kelvin - helmholtz turbulence can not be reached this way . in this paper we present computer simulations where we have let the dust grains , represented by particles each with an individual velocity vector and position , move relative to the gas . this allows us to obtain a state of self - sustained kelvin - helmholtz turbulence from which we can measure quantities such as the diffusion coefficient and the maximum dust density . a better knowledge of these important characteristics of kelvin - helmholtz turbulence is vital for our understanding of planet formation .	a two - dimensional corotating slice in the azimuthal vertical plane of the disk is considered where we include the coriolis force and the radial advection of the keplerian rotation flow . the azimuthally averaged state of the self - sustained kelvin - helmholtz turbulence is found to have a constant richardson number in the region around the mid - plane where the dust - to - gas ratio is significant .	we perform numerical simulations of the kelvin - helmholtz instability in the mid - plane of a protoplanetary disk . a two - dimensional corotating slice in the azimuthal vertical plane of the disk is considered where we include the coriolis force and the radial advection of the keplerian rotation flow . dust grains , treated as individual particles , move under the influence of friction with the gas , while the gas is treated as a compressible fluid . the friction force from the dust grains on the gas leads to a vertical shear in the gas rotation velocity . as the particles settle around the mid - plane due to gravity , the shear increases , and eventually the flow becomes unstable to the kelvin - helmholtz instability . the kelvin - helmholtz turbulence saturates when the vertical settling of the dust is balanced by the turbulent diffusion away from the mid - plane . the azimuthally averaged state of the self - sustained kelvin - helmholtz turbulence is found to have a constant richardson number in the region around the mid - plane where the dust - to - gas ratio is significant . nevertheless the dust density has a strong non - axisymmetric component . we identify a powerful clumping mechanism , caused by the dependence of the rotation velocity of the dust grains on the dust - to - gas ratio , as the source of the non - axisymmetry . our simulations confirm recent findings that the critical richardson number for kelvin - helmholtz instability is around unity or larger , rather than the classical value of 1/4 .
0707.2636	i	we have observed ngc 6946 as part of a program of deep mapping of extended , cold co in nearby spiral galaxies @xcite . large , fully - sampled , and deep images of co in nearby galaxies are relatively uncommon . interferometric images either do not contain zero spacing data ( e.g. , * ? ? ? * ) or if they do , the images typically do not go deep enough to detect cold , molecular disk gas . the detection of cold , extended molecular gas at large galactocentric radii in large spirals is a goal of this mapping project with the nrao 12 meter telescope . a gas - rich sc galaxy at a distance of 6 mpc @xcite , ngc 6946 is known for its bright and asymmetric optical spiral arms @xcite . the pronounced asymmetry may be caused by interactions with neighboring dwarf galaxies , ugc 11583 and l149 @xcite . ngc 6946 has a 9 optical diameter on the sky and an atomic hydrogen ( hi ) gas disk extending to 25 @xcite . like many spirals , ngc 6946 has a central @xmath5 diameter hole " in its hi disk . radio continuum , far infrared ( fir ) , optical line , and x - ray observations indicate vigorous star formation in the disk and an interstellar medium ( ism ) stirred by supernovae and stellar winds @xcite . the high level of star formation in the disk of ngc 6946 has been attributed both to its strong spiral density wave @xcite , and to stochastic , self - propagating , star formation @xcite . until recently , the co morphology beyond the inner 3 radius ( @xmath65 kpc ) was not well known . like many spiral galaxies , ngc 6946 has a bright nuclear co peak which falls off nearly exponentially with galactocentric radius @xcite . a 3 diameter map of @xcite revealed substantial co emission in the inner disk with several emission peaks . @xcite mapped two 2 circular fields in the disk of ngc 6946 in a study of arm and interarm regions . the inner 2 region has been mapped with higher resolution single dish and aperture synthesis telescopes in transitions of co and co isotopomers @xcite . a larger interferometer+single dish map of ngc 6946 has been made by the bima song team @xcite , although with lower sensitivity to cold extended emission than the maps we present here . @xcite presented 21 resolution fully - sampled single dish maps of co(1 - 0 ) . we compare our results to theirs . the on the fly " ( otf ) observing mode at the nrao was ideally suited to the imaging of extended gas in galaxies . here , we present 16 by 10 maps of co(1 - 0 ) and co(2 - 1 ) covering the optical disk of ngc 6946 made with the 12 meter telescope . the maps are deep enough to detect cold , extended interarm co to levels of @xmath7 , or @xmath8 . we use these primary tracers of the molecular gas phase and combine them with archival and published data in order to study the molecular gas disk , the total neutral gas surface density , and their relationship to star formation in the disk of ngc 6946 .	we present on the fly " maps of the co(1 - 0 ) and co(2 - 1 ) emission covering a 10 10 region of the ngc 6946 . using our co maps and archival vla hi observations we create a total gas surface density map , , for ngc 6946 . the predominantly molecular inner gas disk transitions smoothly into an atomic outer gas disk , with equivalent atomic and molecular gas surface densities at r = 3.5 ( 6 kpc ) . star formation tracers are better correlated with the total neutral gas disk than with the molecular gas by itself implying . using the 100 and 21 cm continuum from ngc 6946 as star formation tracers , we arrive at a gas consumption timescale of 2.8 gyr , which is relatively uniform across the disk .	we present on the fly " maps of the co(1 - 0 ) and co(2 - 1 ) emission covering a 10 10 region of the ngc 6946 . using our co maps and archival vla hi observations we create a total gas surface density map , , for ngc 6946 . the predominantly molecular inner gas disk transitions smoothly into an atomic outer gas disk , with equivalent atomic and molecular gas surface densities at r = 3.5 ( 6 kpc ) . we estimate that the total mass is , roughly 1/3 of the interstellar hydrogen gas mass , and about 2% of the dynamical mass of the galaxy at our assumed distance of 6 mpc . the value of the co(2 - 1)/co(1 - 0 ) line ratio ranges from 0.35 to 2 ; 50% of the map is covered by very high ratio , , gas . the very high ratios are predominantly from interarm regions and appear to indicate the presence of wide - spread optically thin gas . star formation tracers are better correlated with the total neutral gas disk than with the molecular gas by itself implying . using the 100 and 21 cm continuum from ngc 6946 as star formation tracers , we arrive at a gas consumption timescale of 2.8 gyr , which is relatively uniform across the disk . the high star formation rate at the nucleus appears to be due to a large accumulation of molecular gas rather than a large increase in the star formation efficiency . the mid - plane gas pressure in the outer ( r 10 kpc ) hi arms of ngc 6946 is close to the value at the radial limit ( 10 kpc ) of our observed co disk . if the mid - plane gas pressure is a factor for the formation of molecular clouds , these outer hi gas arms should contain molecular gas which we do not see because they are beyond our detection limit .
0707.2636	c	we have obtained deep co(1 - 0 ) and co(2 - 1 ) images of a 10 @xmath0 10 region centered on the sc galaxy , ngc 6946 , with 55 and 27 resolution using the nrao 12 meter telescope . we have combined these deep co images with vla hi images to obtain images of the neutral gas in this galaxy . to summarize our findings : + 1 ) the co(1 - 0 ) and co(2 - 1 ) disks shows many of the same features seen in the optical disk : a strong nuclear peak of emission , molecular gas arms spatially coincident with the asymmetric optical arm pattern , and a 10 diameter inner disk filled with co emission . the co disk is roughly exponential with a scale length of @xmath77 or @xmath134 kpc . + 2 ) we obtain @xmath135 for the molecular hydrogen gas mass of ngc 6946 . this can be compared to the total atomic hydrogen gas mass of @xmath136 ( which includes a vla missing flux estimate ) . molecular hydrogen constitutes 1/3 of the interstellar hydrogen gas mass and 2% of the dynamical mass of ngc 6946 . at the nucleus , = 170 , the molecular gas surface density is @xmath47 along the strong optical arm pattern , and @xmath137 regions beyond . + 3 ) the mean value for @xmath138 in the the nucleus and optical arm pattern is @xmath139 . this is consistent with optically thick gas , with an excitation temperature of 10 - 15 k. interarm co shows the largest variation in , with a range of 0.35 to 2 . only 4% of the co ratio map has @xmath68 which is likely to be cold or subthermally excited co ( @xmath140 k ) . fully half of the co disk of ngc 6946 has @xmath65 . the high appears to indicate the presence of widespread , optically - thin gas in between the spiral arms . + 4 ) molecular gas dominates the total gas surface density within a galactocentric radius of 3.5 ( 6 kpc ) . co emission fills the central depression in the hi disk . beyond the nuclear region , there is a good correlation between the co and hi gas , which both peak on the spiral arms . the inner disk arm pattern transitions smoothly from predominantly co arms to predominantly hi arms at the outskirts of the co disk . at the nucleus , = 240 , the total gas surface density is @xmath141 along the optical arm pattern , and @xmath142 along the outer gas arms ( @xmath143 ) . co(2 - 1 ) emission peaks are coincident with clumps of hi , , and fir emission outside the nuclear region , presumably an indication of warmer molecular gas and dissociated . + 5 ) we find strong correlations between star formation tracers ( except for ) and co emission in ngc 6946 . the correlation coefficients are @xmath144 . when is used instead of just the molecular gas tracer in a radial comparison , the dependence on galactic radius is reduced . star formation is more closely related to the total gas surface density than the molecular gas surface density alone , a schmidt law relationship . this also implies star formation is likely well beyond the radial limits of our observed co disk in regions of predominantly hi gas . surprisingly , is not as well correlated with co or as are the other star formation tracers . the correlation coefficient is significantly less , @xmath88 , and the ratio formed from and co or declines more rapidly with galactic radius . + 6 ) the star formation efficiency in the disk of ngc 6946 is relatively uniform ; 2.8 gyr when expressed in terms of the gas consumption time - scale . this uniformity implies @xmath3 . the star formation rate at the nucleus is due to the high molecular surface density rather than an elevated star formation efficiency . + 7 ) the edge of the observed co disk represents a detection limit rather than a threshold for molecular cloud formation . we suspect the exponential fall of the co disk continues smoothly past our detection limit . the mid - plane gas pressure in the outer hi arm structure , @xmath133 is close to the value at the limits of the observed co disk . these gas arms should support the formation of molecular clouds which could be detectable in higher resolution observations . the authors would like to thank the nrao 12 m telescope operators , duane clark , paul hart , victor gasho and harry stahl , for their help and company during the many observing sessions in which the data for ngc 6946 and other galaxies were acquired . we thank l. tacconi giving for us permission to retrieve and use the hi 21 cm line observations from the vla archive . and we appreciate the careful reading and critical suggestions made by the anonymous referee . this work was supported in part by nsf grants ast00 - 71276 and ast03 - 07950 . we made use of the nasa / ipac / iras hires data reduction facilities as well as stsci digital sky survey facilities . the digitized sky surveys were produced at the space telescope science institute under u.s . government grant nag w-2166 . adler , d. s. , allen , r. j. , & lo , k. y. 1991 , , 283 , 475 arp , h. 1966 , , 14 , 1 arsenault , r. 1989 , , 217 , 66 ball , r. , et al . 1985 , , 298 , l21 bell , e.f . 2003 , , 586 , 794 belley , j. & roy , j. 1992 , , 78 , 61 bicay , m.d . , helou , g. & condon , j.j . 1989 , , 338 , l53 bicay , m.d . & helou , g. 1990 , , 362 , 59 boulanger , f. & viallefond , f. 1992 , , 266 , 37 carignan , c. , et al . 1990 , , 234 , 43 casoli , f. , et al . 1990 , , 233 , 357 castets , a. , et al . 1990 , , 234 , 469 catalogued galaxies and quasars in the iras survey 1985 , prepared by lonsdale , c.j . 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( j2000 ) & @xmath145 + dec . ( j2000 ) & @xmath146 + @xmath147 & @xmath148 + distance & 6 mpc + @xmath149 & 50.5 @xmath150 + inclination & 40@xmath151 + position angle & 242@xmath152 + @xmath153 & 170 @xmath154 + @xmath155 & 5.1@xmath156 ( 9.0 kpc ) + @xmath157 & 1.07 @xmath158 + @xmath159 & @xmath160 + @xmath161 & @xmath162 + @xmath163 & @xmath164 + @xmath165 & @xmath166 + @xmath167 & @xmath168 + & hubble type & scd & scd & sbc & sbbc + distance ( mpc ) & 3.3 & 6 & 4 & ... + d@xmath84 ( arcminutes ) & 20 & 11 & 11 & ... + d@xmath84/d@xmath169 & 0.23 & 0.38 & 0.15 & ... + d@xmath84/d@xmath170 & 1.1 & 1.0 & 1.0 & ... + m@xmath171 ( @xmath172 ) & 1.8 & 1.9 & 0.7 & @xmath57 + @xmath173 ( @xmath174 ) & 16 & 33 & 23 & 25 + @xmath173 ( @xmath174 ) & 57 & 70 & 62 & 48 + / & 0.27 & 0.47 & 0.37 & 0.52 + m@xmath82/m@xmath83 & 0.055 & 0.074 & 0.16 & 0.03 + @xmath175 ( ) & 140 & 170 & 220 & 400 + @xmath176 ( ) & 11 & 13 & 23 & 3.4 + & 100 & -0.196 ( 0.015 ) + & 60 & -0.189 ( 0.015 ) + & 21 cm continuum & -0.170 ( 0.014 ) + & & -0.224 ( 0.015 ) + & & + & 100 & -0.102 ( 0.008 ) + & 60 & -0.095 ( 0.009 ) + & 21 cm continuum & -0.076 ( 0.009 ) + & & -0.130 ( 0.014 ) + & & + & 100 & -0.002 ( 0.006 ) + & 60 & 0.005 ( 0.007 ) + & 21 cm continuum & 0.024 ( 0.007 ) + & & -0.030 ( 0.013 ) +	we estimate that the total mass is , roughly 1/3 of the interstellar hydrogen gas mass , and about 2% of the dynamical mass of the galaxy at our assumed distance of 6 mpc . the high star formation rate at the nucleus appears to be due to a large accumulation of molecular gas rather than a large increase in the star formation efficiency . the mid - plane gas pressure in the outer ( r 10 kpc ) hi arms of ngc 6946 is close to the value at the radial limit ( 10 kpc ) of our observed co disk . if the mid - plane gas pressure is a factor for the formation of molecular clouds , these outer hi gas arms should contain molecular gas which we do not see because they are beyond our detection limit .	we present on the fly " maps of the co(1 - 0 ) and co(2 - 1 ) emission covering a 10 10 region of the ngc 6946 . using our co maps and archival vla hi observations we create a total gas surface density map , , for ngc 6946 . the predominantly molecular inner gas disk transitions smoothly into an atomic outer gas disk , with equivalent atomic and molecular gas surface densities at r = 3.5 ( 6 kpc ) . we estimate that the total mass is , roughly 1/3 of the interstellar hydrogen gas mass , and about 2% of the dynamical mass of the galaxy at our assumed distance of 6 mpc . the value of the co(2 - 1)/co(1 - 0 ) line ratio ranges from 0.35 to 2 ; 50% of the map is covered by very high ratio , , gas . the very high ratios are predominantly from interarm regions and appear to indicate the presence of wide - spread optically thin gas . star formation tracers are better correlated with the total neutral gas disk than with the molecular gas by itself implying . using the 100 and 21 cm continuum from ngc 6946 as star formation tracers , we arrive at a gas consumption timescale of 2.8 gyr , which is relatively uniform across the disk . the high star formation rate at the nucleus appears to be due to a large accumulation of molecular gas rather than a large increase in the star formation efficiency . the mid - plane gas pressure in the outer ( r 10 kpc ) hi arms of ngc 6946 is close to the value at the radial limit ( 10 kpc ) of our observed co disk . if the mid - plane gas pressure is a factor for the formation of molecular clouds , these outer hi gas arms should contain molecular gas which we do not see because they are beyond our detection limit .
1511.00218	i	the understanding of low - energy electronic structures and excitations in real materials is an important subject of condensed - matter physics and material science . interesting phenomena such as a non - fermi - liquid behavior and unconventional superconductivity are caused by the instability of electronic structures near the fermi level . a common feature is often found in the band structures showing such phenomena ; isolated bands appear near the fermi level . the width of these isolated bands is typically the order of 1 ev , which is comparable to local electronic interactions . thus , in these isolated bands , the kinetic and potential energies compete with each other , and the competition is often discussed within a local - interaction approximation , as in the hubbard model . in real materials , however , there exist various elementally excitations not described by the local electronic interaction . the plasmon in metallic systems or the exciton in insulating systems are well known examples of such nonlocal excitations , which result from the long - range coulomb interaction . in the above - mentioned isolated - band systems , the plasmon excitation can occur in this band , and its energy scale can be very small ( of the order of 1 ev ) , which is comparable to the bandwidth and the size of the local coulomb interaction . in this study , we investigate the effect of the low - energy - plasmon fluctuation on the electronic structure of real isolated - band systems from first principles . for this purpose , we choose two materials , a quasi - one dimensional organic conductor ( tmtsf)@xmath1pf@xmath2 ( ref . ) , where tmtsf stands for tetramethyltetraselenafulvalene , and a three - dimensional perovskite transition - metal oxide srvo@xmath3 ( ref . ) . these materials are typical isolated - band systems and are studied as benchmark materials of the correlated metal , where the local coulomb - interaction effect on the electronic properties is investigated with much interest . @xcite in the present work , we focus on the low - energy plasmon effect on the electronic structure . @xcite through the comparison between theoretical and experimental results on the plasmon - related properties and spectral functions , we verify low - energy plasmon effects on the electronic structure of the real system . the organic conductor ( tmtsf)@xmath1pf@xmath2 is a representative quasi - one - dimensional material , @xcite and basically behaves as a good metallic conductor . @xcite at low temperature ( around 12 k ) , it undergoes a transition to a spin - density - wave phase . @xcite in the high - temperature metallic region , photoemission spectroscopy has observed small spectral weight near the fermi level . @xcite from this observation and the quasi - one - dimensional nature , the origin of the renormalization has been discussed in view of the tomonaga - luttinger liquid . @xcite on the other hand , this material exhibits clear low - energy plasma edges around 0.1 - 1 ev in the reflectance spectra . @xcite therefore , this plasmon excitation would also be a prominent renormalization factor of the electronic structure . the transition - metal oxide srvo@xmath3 is another well known correlated metal . @xcite many high - resolution photoemission measurements @xcite including the bulk - sensitive version @xcite were performed and clarified a strong renormalization of the low - energy isolated band and the satellite peak just below this band . the origin has actively been discussed in terms of the local electronic correlation . @xcite on the other hand , the reflectance and electron - energy - loss spectra have clarified low - energy plasmon excitations around 1.4 ev . @xcite in density - functional band structure , srvo@xmath3 has isolated bands of the @xmath4 orbitals around the fermi level , whose bandwidth is about 2.7 ev . @xcite also , the constrained random phase approximation gives an estimate of the local electronic interaction of @xmath52 - 3 ev . @xcite thus , the energy scale of the experimentally observed plasmon excitation is comparable to the bandwidth and the local coulomb interaction . hence , the low - energy plasmon fluctuation would certainly be relevant to the low - energy properties . to study how the plasmon excitation affects the electronic structure , we perform _ ab initio _ calculations based on the @xmath0 approximation . @xcite the @xmath0 calculation considers the self - energy effect due to the plasmon fluctuation and describes properly quasiparticle energies in the valence region . on the other hand , the description for the plasmon satellite in the spectral function is known to be less accurate . @xcite in order to improve this deficiency , _ ab initio _ @xmath0 plus cumulant ( @xmath0+@xmath6 ) calculations have recently been performed . @xcite the accuracy of the @xmath0+@xmath6 method has been verified in bulk silicon @xcite and simple metals , @xcite where the satellite property is satisfactorily improved . in the present study , we apply the @xmath0+@xmath6 method to the study of the above mentioned isolated - band systems , and show that the low - energy plasmon fluctuations modify substantially the low - energy electronic structure . the present paper is organized as follows . in sec . ii , we describe the @xmath0 and @xmath0+@xmath6 methods to calculate dielectric and spectral properties . computational details and results for ( tmtsf)@xmath1pf@xmath2 and srvo@xmath3 are given in sec . we also discuss the comparison between theory and experiment , focusing on the renormalization of the electronic structure due to the plasmon excitation . the summary is given in sec .	we present _ ab initio _ these materials exhibit characteristic low - energy band structures around the fermi level , which bring about interesting low - energy properties ; the low - energy bands near the fermi level are isolated from the other bands and , in the isolated bands , unusually low - energy plasmon excitations occur . to study the effect of this low - energy - plasmon fluctuation on the electronic structure , we calculate spectral functions and photoemission spectra using the _ ab initio _ cumulant expansion of the green s function based on the self - energy .	we present _ ab initio _ plus cumulant - expansion calculations for an organic compound ( tmtsf)pf and a transition - metal oxide srvo . these materials exhibit characteristic low - energy band structures around the fermi level , which bring about interesting low - energy properties ; the low - energy bands near the fermi level are isolated from the other bands and , in the isolated bands , unusually low - energy plasmon excitations occur . to study the effect of this low - energy - plasmon fluctuation on the electronic structure , we calculate spectral functions and photoemission spectra using the _ ab initio _ cumulant expansion of the green s function based on the self - energy . we found that the low - energy plasmon fluctuation leads to an appreciable renormalization of the low - energy bands and a transfer of the spectral weight into the incoherent part , thus resulting in an agreement with experimental photoemission data .
1511.00218	c	we have performed _ ab initio _ @xmath0 plus cumulant - expansion calculations for an organic conductor ( tmtsf)@xmath1pf@xmath2 and a transition - metal oxide srvo@xmath3 to study the low - energy plasmon - fluctuation effect on the electronic structure . the bands around the fermi level of these materials are isolated from the other bands , and the low - energy plasmon excitations derived from these isolated bands exist . our calculated reflectance spectra well identify the experimental low - energy plasmon peaks . by calculating the cumulant - expanded green s function based on the @xmath0 approximation to the self - energy , we have simulated spectral functions and compare them with photoemission data . we have found agreements between them , indicating that the low - energy plasmon excitation certainly affects the low - energy electronic structure ; it reduces the quasiparticle spectral weight around the fermi level and leads to the weight transfer to the satellite parts . this effect was found to be more or less appreciable in ( tmtsf)@xmath1pf@xmath2 than in srvo@xmath3 . in particular , in ( tmtsf)@xmath1pf@xmath2 , the spectrum at the standard @xmath0 level exhibits a clear plasmaron state , but considering the plasmon - fluctuation effects not treated in the standard @xmath0 calculation leads to the disappearance of the state in the @xmath7 . since the low - energy isolated - band structure is commonly found in various materials , the low - energy plasmon effect pursued in the present work can provide a basis for understanding the electronic structure of real systems . the recent progress in the photoemission experiment for the correlated materials ( refs . ) requires a concomitant progress on the theoretical side and the present _ ab initio _ many - body calculations would provide firm basis for them . in the present study , we have focused on the long - range correlation and treated it effectively with the cumulant - expansion method , while the short - ranged correlation , which is appropriately described by the @xmath185-matrix framework , is neglected . this is a future challenge which remains to be explored . in addition , recent photoemission spectroscopy reveals appreciable differences in the electronic structure between the bulk and thin film systems . @xcite the electronic structure of the surface is very sensitive to the atomic configurations at the surface @xcite and therefore careful analyses for the atomic structure and its effect on electronic structure are required . the _ ab initio _ calculations for the surface effect are clearly important for the deep understanding of the spectroscopy of the real materials . this is also a future challenge . we would like to thank norikazu tomita and teppei yoshida for useful discussions . calculations were done at supercomputer center at institute for solid state physics , university of tokyo . this work was supported by grants - in - aid for scientific research ( no . 22740215 , 22104010 , 23110708 , 23340095 , 23510120 , 25800200 ) from mext , japan , and consolidator grant correlmat of the european research council ( project number 617196 ) .	plus cumulant - expansion calculations for an organic compound ( tmtsf)pf and a transition - metal oxide srvo . we found that the low - energy plasmon fluctuation leads to an appreciable renormalization of the low - energy bands and a transfer of the spectral weight into the incoherent part , thus resulting in an agreement with experimental photoemission data .	we present _ ab initio _ plus cumulant - expansion calculations for an organic compound ( tmtsf)pf and a transition - metal oxide srvo . these materials exhibit characteristic low - energy band structures around the fermi level , which bring about interesting low - energy properties ; the low - energy bands near the fermi level are isolated from the other bands and , in the isolated bands , unusually low - energy plasmon excitations occur . to study the effect of this low - energy - plasmon fluctuation on the electronic structure , we calculate spectral functions and photoemission spectra using the _ ab initio _ cumulant expansion of the green s function based on the self - energy . we found that the low - energy plasmon fluctuation leads to an appreciable renormalization of the low - energy bands and a transfer of the spectral weight into the incoherent part , thus resulting in an agreement with experimental photoemission data .
astro-ph0703769	i	we present a catalog of variable stars within @xmath6 pc of sgr a * in the near - infrared @xmath1 and @xmath2 bands over a three - year baseline ; @xmath153% of these variables are previously unidentfied . this is the first photometric variability study of the galactic center to use the technique of image subtraction . we find several new periodic sources . of these , psd j174535.60 - 290035.4 and psd j174538.34 - 290036.7 have the shortest periods , with @xmath154 days . we believe psd j174535.60 - 290035.4 is a pulsating variable , though it is unlikely to be a cepheid . psd j174538.34 - 290036.7 appears to be a nearly edge - on contact eclipsing binary system , in which case the period is actually @xmath155 days and the individual components are likely to be quite large . another periodic source , psd j174540.16 - 290055.7 ( @xmath156 days ) , is coincident with the x - ray variable cxogc j174540.1 - 290055 ; we suspect that this source is a cataclysmic variable . among the previously identified sources in the catalog , we associate irs 10 * with a bright x - ray point source and oh , h@xmath4o , and sio masers , suggesting that it is an agb star with an accreting companion . and @xmath2 , sorted by ra as in table [ tbl : vary ] . for each source , the extent of the @xmath1- and @xmath2-band ranges plotted is the same . points lying below the magnitude limit ( see [ sec : analysis ] ) are not included.[fig : lcs ] ] lrrrrl psd j174535.45 - 290007.6 & @xmath157 & @xmath158 & 12.6 & & + psd j174535.89 - 290113.5 & @xmath159 & @xmath160 & 14.2 & 10.9 & + psd j174535.98 - 290011.5 & @xmath161 & @xmath162 & 12.1 & 9.7 & + psd j174536.18 - 290047.6 & @xmath163 & @xmath164 & 12.4 & 9.6 & + psd j174536.53 - 290125.9 & @xmath165 & @xmath166 & 11.9 & 9.5 & + psd j174536.63 - 290015.4 & @xmath167 & @xmath168 & 10.7 & 8.8 & + psd j174536.85 - 290114.5 & @xmath169 & @xmath170 & 13.1 & 10.1 & + psd j174536.97 - 290138.0 & @xmath171 & @xmath172 & 15.0 & 10.2 & + psd j174536.97 - 290019.4 & @xmath173 & @xmath174 & 12.5 & 10.0 & + psd j174537.10 - 290103.9 & @xmath175 & @xmath176 & 13.9 & 10.8 & + psd j174537.24 - 290045.7 & @xmath177 & @xmath178 & 12.6 & 9.9 & v4910 sgr + psd j174537.42 - 290042.2 & @xmath179 & @xmath180 & 13.8 & 10.6 & + psd j174537.52 - 290046.2 & @xmath181 & @xmath182 & 14.5 & 10.6 & + psd j174537.52 - 290041.7 & @xmath183 & @xmath184 & 12.8 & 10.0 & + psd j174537.66 - 285955.2 & @xmath185 & @xmath186 & 12.7 & & + psd j174537.74 - 290009.2 & @xmath187 & @xmath188 & 13.1 & 10.2 & + psd j174537.91 - 290045.9 & @xmath189 & @xmath190 & 12.7 & 10.0 & + psd j174537.98 - 290134.4 & @xmath191 & @xmath192 & 9.5 & 8.6 & cxogc j174537.9 - 290134 + psd j174537.98 - 290004.4 & @xmath191 & @xmath193 & 12.0 & 9.2 & + psd j174538.02 - 290102.6 & @xmath194 & @xmath195 & 12.5 & 9.3 & v4911 sgr ; blended + psd j174538.05 - 290058.1 & @xmath196 & @xmath197 & 12.7 & 10.2 & + psd j174538.10 - 290033.5 & @xmath198 & @xmath199 & 13.3 & 10.3 & + psd j174538.19 - 290005.0 & @xmath200 & @xmath201 & 12.5 & 9.7 & + psd j174538.29 - 290011.1 & @xmath202 & @xmath203 & 13.4 & 9.9 & + psd j174538.61 - 290054.3 & @xmath204 & @xmath205 & 13.0 & 9.5 & + psd j174538.74 - 290012.7 & @xmath206 & @xmath207 & 11.1 & 9.2 & + psd j174538.79 - 290004.6 & @xmath208 & @xmath209 & 11.8 & 9.3 & + psd j174538.95 - 290139.6 & @xmath210 & @xmath211 & & 9.4 & + psd j174538.99 - 290102.2 & @xmath212 & @xmath213 & 14.3 & 12.4 & + psd j174539.09 - 290039.3 & @xmath214 & @xmath215 & 12.7 & 9.8 & blended + psd j174539.23 - 290036.3 & @xmath216 & @xmath217 & 14.1 & 10.8 & + psd j174539.31 - 290016.3 & @xmath218 & @xmath219 & 11.6 & 9.2 & cxogc j174539.3 - 290016 + psd j174539.31 - 290054.1 & @xmath218 & @xmath220 & 12.6 & 10.0 & + psd j174539.36 - 290055.6 & @xmath221 & @xmath222 & 13.0 & 10.5 & + psd j174539.39 - 290014.6 & @xmath223 & @xmath224 & 10.9 & 8.4 & blended + psd j174539.45 - 290056.6 & @xmath225 & @xmath226 & 12.4 & 9.1 & blended + psd j174539.56 - 290057.3 & @xmath227 & @xmath228 & & 12.5 & + psd j174539.58 - 290049.5 & @xmath229 & @xmath230 & 12.4 & 9.6 & + psd j174539.60 - 290107.6 & @xmath231 & @xmath232 & 15.3 & 11.8 & @xmath1 past threshold + psd j174539.73 - 290050.2 & @xmath233 & @xmath234 & 12.5 & 9.9 & + psd j174539.75 - 290055.5 & @xmath235 & @xmath236 & 12.5 & 9.6 & irs 22 + psd j174539.76 - 290026.4 & @xmath237 & @xmath238 & 14.1 & 10.6 & irs 34w + psd j174539.77 - 290043.9 & @xmath239 & @xmath240 & 12.1 & 9.6 & + psd j174539.79 - 290008.5 & @xmath241 & @xmath242 & 11.4 & 8.5 & + psd j174539.79 - 290029.9 & @xmath241 & @xmath243 & 13.2 & 10.6 & irs 13e + psd j174539.83 - 290053.9 & @xmath244 & @xmath245 & 9.6 & 7.6 & blended + psd j174539.86 - 290024.7 & @xmath246 & @xmath247 & & 10.5 & + psd j174539.86 - 290019.7 & @xmath248 & @xmath249 & 12.8 & 10.0 & + psd j174539.90 - 290034.5 & @xmath250 & @xmath251 & 13.3 & 10.6 & blended + psd j174539.91 - 290011.0 & @xmath247 & @xmath252 & 12.5 & 9.9 & cxogc j174539.9 - 290012 + psd j174539.93 - 290024.9 & @xmath253 & @xmath254 & 13.9 & 10.5 & + psd j174539.95 - 285951.1 & @xmath255 & @xmath256 & 12.2 & & + psd j174539.95 - 290110.8 & @xmath257 & @xmath258 & 14.2 & 10.2 & + psd j174539.99 - 290016.5 & @xmath259 & @xmath260 & 12.1 & 9.8 & irs 15sw + psd j174540.02 - 290037.2 & @xmath261 & @xmath262 & 11.8 & 9.4 & irs 14sw + psd j174540.04 - 290018.0 & @xmath263 & @xmath264 & 12.3 & 10.3 & irs 15ne + psd j174540.04 - 290022.7 & @xmath263 & @xmath263 & 9.0 & & irs 7 , saturated in @xmath2 + psd j174540.04 - 290027.0 & @xmath263 & @xmath235 & 11.6 & 9.3 & irs 16nw + psd j174540.04 - 290019.5 & @xmath265 & @xmath266 & 12.6 & & + psd j174540.06 - 290112.1 & @xmath267 & @xmath268 & 12.0 & 9.9 & + psd j174540.11 - 290036.4 & @xmath269 & @xmath270 & 11.8 & 9.1 & irs 14ne + psd j174540.21 - 290043.2 & @xmath271 & @xmath272 & 14.1 & 10.7 & + psd j174540.21 - 290056.3 & @xmath271 & @xmath273 & 15.6 & & + psd j174540.31 - 285953.8 & @xmath274 & @xmath275 & 13.0 & & + psd j174540.31 - 290039.5 & @xmath274 & @xmath276 & 12.3 & 9.4 & + psd j174540.37 - 285954.0 & @xmath277 & @xmath278 & 11.7 & & blended + psd j174540.38 - 290033.6 & @xmath279 & @xmath199 & & 11.4 & + psd j174540.45 - 290036.3 & @xmath260 & @xmath217 & 13.8 & 11.1 & cxogc j174540.4 - 290036 + psd j174540.47 - 290034.6 & @xmath219 & @xmath280 & 11.3 & 8.6 & irs 9 , blended + psd j174540.58 - 290026.7 & @xmath281 & @xmath239 & 11.9 & 9.2 & irs 1ne + psd j174540.64 - 290023.6 & @xmath282 & @xmath255 & & 10.2 & irs 10 * , blended + psd j174540.83 - 290034.0 & @xmath283 & @xmath284 & 12.2 & 9.1 & irs 28 + psd j174540.84 - 290027.0 & @xmath285 & @xmath286 & 12.0 & 9.5 & irs 32 + psd j174541.04 - 290022.7 & @xmath287 & @xmath263 & 11.1 & 8.5 & + psd j174541.09 - 285952.6 & @xmath288 & @xmath289 & 13.2 & & + psd j174541.17 - 290046.9 & @xmath290 & @xmath291 & 10.7 & 7.9 & irs 19 , blended + psd j174541.20 - 290039.0 & @xmath292 & @xmath210 & 11.6 & 9.1 & + psd j174541.27 - 290049.9 & @xmath293 & @xmath294 & 12.8 & 9.6 & + psd j174541.35 - 290033.0 & @xmath295 & @xmath296 & 13.2 & 10.2 & + psd j174541.36 - 290022.7 & @xmath297 & @xmath298 & 11.9 & 9.4 & + psd j174541.39 - 290126.6 & @xmath299 & @xmath300 & 13.9 & 9.6 & + psd j174541.56 - 285949.6 & @xmath301 & @xmath302 & 12.4 & & + psd j174541.59 - 290023.0 & @xmath303 & @xmath304 & 13.7 & 10.8 & + psd j174541.75 - 290004.6 & @xmath305 & @xmath209 & 12.1 & 9.0 & + psd j174541.75 - 290013.0 & @xmath305 & @xmath306 & 12.3 & 9.3 & + psd j174542.01 - 290024.4 & @xmath307 & @xmath308 & 13.2 & 10.0 & + psd j174542.13 - 290045.8 & @xmath309 & @xmath310 & 13.5 & 10.3 & + psd j174542.39 - 285950.7 & @xmath311 & @xmath312 & 10.8 & & + psd j174542.60 - 290103.9 & @xmath313 & @xmath176 & 14.3 & 11.0 & + psd j174542.72 - 285957.4 & @xmath314 & @xmath315 & 10.5 & 7.7 & v4928 sgr , blended + psd j174542.76 - 290125.5 & @xmath316 & @xmath317 & 10.7 & 8.7 & + psd j174542.88 - 285951.3 & @xmath318 & @xmath319 & 12.7 & & + psd j174542.92 - 285958.4 & @xmath320 & @xmath321 & 14.2 & 11.8 & + psd j174543.01 - 290011.9 & @xmath322 & @xmath323 & 10.8 & 8.5 & + psd j174543.19 - 290013.0 & @xmath324 & @xmath306 & 10.9 & 8.2 & v4930 sgr , blended + psd j174543.29 - 290118.8 & @xmath325 & @xmath326 & & 11.9 & + psd j174543.31 - 290014.3 & @xmath327 & @xmath328 & 14.8 & 12.6 & + psd j174543.50 - 290005.3 & @xmath329 & @xmath292 & & 9.0 & + lrrrrrl psd j174535.60 - 290035.4 & @xmath330 & @xmath331 & 14.5 & 12.3 & @xmath332 & cxogc j174535.6 - 290034 + psd j174537.11 - 290033.1 & @xmath333 & @xmath296 & 10.0 & 12.8 & @xmath334 & + psd j174538.28 - 290006.8 & @xmath335 & @xmath336 & 11.9 & 9.3 & @xmath337 & + psd j174538.35 - 290036.7 & @xmath338 & @xmath339 & 14.9 & 12.1 & @xmath340 & + psd j174538.97 - 290123.7 & @xmath341 & @xmath161 & 14.6 & 10.8 & @xmath342 & + psd j174538.98 - 290007.7 & @xmath343 & @xmath287 & 13.0 & 9.9 & @xmath344 & + psd j174539.39 - 290039.5 & @xmath345 & @xmath346 & 11.9 & 9.8 & @xmath347 & + psd j174539.79 - 290035.2 & @xmath348 & @xmath349 & 11.8 & 8.8 & @xmath350 & irs 12n , very blended + psd j174540.12 - 290029.6 & @xmath351 & @xmath352 & 10.8 & 8.3 & @xmath353 & irs 16sw + psd j174540.13 - 290016.8 & @xmath354 & @xmath355 & 12.1 & 9.4 & @xmath356 & irs 15n , blended + psd j174540.16 - 290055.7 & @xmath357 & @xmath358 & 12.1 & 9.3 & @xmath359 & cxogc j174540.1 - 290055 + psd j174542.36 - 290011.2 & @xmath360 & @xmath203 & 13.4 & 10.6 & @xmath361 & + psd j174540.25 - 290027.2 & @xmath266 & @xmath233 & 10.5 & 8.3 & @xmath362 & irs 16ne + psd j174543.14 - 290050.2 & @xmath363 & @xmath234 & 12.0 & 9.1 & @xmath364 & blended + lllcl @xcite & @xmath365 & 1991 , 1992 , 1993 ; & @xmath2 & irs 9 , 10 * , 12n , 14sw , 28 + & & 3 epochs & & + @xcite & central @xmath366 & may 1993april 1995 ; & @xmath367 , @xmath1 , @xmath2 , @xmath368 & irs 7 , 9 , 12n + & & 58 epochs & & + @xcite & @xmath369 & august 1992may 1998 ; & @xmath2 & irs 7 , 9 , 10 * , 12n , 16sw and + & & @xmath370 epochs & & potentially irs 1ne , 6 , 14sw + @xcite & @xmath371 & 19941997 ; @xmath372 epochs & @xmath2 & only large - amplitude , + & & & & periodic variability + @xcite & @xmath373 & 19952005 ; 50 epochs & @xmath2 & irs 16sw , 16nw , 16cc , 29n , + & & & & and 12 s stars lllll irs 1ne & [ fig : lcs](d ) & & & psd j174540.58 - 290026.7 + irs 7 & [ fig : lch ] & & lpv & psd j174540.04 - 290022.7 + irs 9 & [ fig : lcs](d ) & & lpv & psd j174540.47 - 290034.6 + irs 10 * & [ fig : lck ] & & oh / ir , x - ray source & psd j174540.64 - 290023.6 + irs 12n & [ fig : periodic ] & @xmath350 & lpv & psd j174539.79 - 290035.2 + irs 14sw & [ fig : lcs](d ) & & & psd j174540.02 - 290037.2 + irs 14ne & [ fig : lcs](d ) & & agb & psd j174540.11 - 290036.4 + irs 15sw & [ fig : lcs](c ) & & wr & psd j174539.99 - 290016.5 + irs 16ne & [ fig : periodic ] & @xmath362 & lbv ? & psd j174540.25 - 290027.2 + irs 16sw & [ fig : periodic ] & @xmath374 & binary & psd j174540.12 - 290029.6 + irs 28 & [ fig : lcs](d ) & & & psd j174540.83 - 290034.0 + irs 34w & [ fig : lcs](c ) & & lbv ? & psd j174539.76 - 290026.4 + v4910 sgr & [ fig : lcs](a ) & & & psd j174537.24 - 290045.7 + v4911 sgr & [ fig : lcs](b ) & & sio maser ? & psd j174538.02 - 290102.6 + v4928 sgr & [ fig : lcs](e ) & & oh / ir & psd j174542.72 - 285957.4 + v4930 sgr & [ fig : lcs](e ) & & mira & psd j174543.19 - 290013.0 + psd j174535.60 - 290035.4 & [ fig : periodic ] & @xmath332 & & + psd j174538.34 - 290036.7 & [ fig : periodic ] & @xmath340 & binary ? ? & + psd j174538.98 - 290007.7 & [ fig : periodic ] & @xmath344 & lpv ? & + psd j174537.98 - 290134.4 & [ fig : lcs](a ) & & x - ray source & + psd j174539.31 - 290016.3 & [ fig : lcs](b ) & & x - ray source & + psd j174540.16 - 290055.7 & [ fig : periodic ] & @xmath359 & variable x - ray & + psd j174541.39 - 290126.6 & [ fig : lcs](e ) & & oh / ir & + psd j174542.36 - 290011.2 & [ fig : periodic ] & @xmath361 & & + psd j174543.14 - 290050.2 & [ fig : periodic ] & @xmath364 & & + , d. l. , atwood , b. , belville , s. r. , brewer , d. f. , byard , p. l. , gould , a. , mason , j. a. , obrien , t. p. , pappalardo , d. p. , pogge , r. w. , steinbrecher , d. p. , & teiga , e. j. 2003 , in instrument design and performance for optical / infrared ground - based telescopes . edited by iye , masanori ; moorwood , alan f. m. proceedings of the spie , volume 4841 , pp . 827 - 838 ( 2003 ) . , m. iye & a. f. m. moorwood , 827838 , f. , genzel , r. , alexander , t. , abuter , r. , paumard , t. , ott , t. , gilbert , a. , gillessen , s. , horrobin , m. , trippe , s. , bonnet , h. , dumas , c. , hubin , n. , kaufer , a. , kissler - patig , m. , monnet , g. , strbele , s. , szeifert , t. , eckart , a. , schdel , r. , & zucker , s. 2005 , , 628 , 246 , t. , genzel , r. , martins , f. , nayakshin , s. , beloborodov , a. m. , levin , y. , trippe , s. , eisenhauer , f. , ott , t. , gillessen , s. , abuter , r. , cuadra , j. , alexander , t. , & sternberg , a. 2006 , , 643 , 1011 , m. f. , cutri , r. m. , stiening , r. , weinberg , m. d. , schneider , s. , carpenter , j. m. , beichman , c. , capps , r. , chester , t. , elias , j. , huchra , j. , liebert , j. , lonsdale , c. , monet , d. g. , price , s. , seitzer , p. , jarrett , t. , kirkpatrick , j. d. , gizis , j. e. , howard , e. , evans , t. , fowler , j. , fullmer , l. , hurt , r. , light , r. , kopan , e. l. , marsh , k. a. , mccallon , h. l. , tam , r. , van dyk , s. , & wheelock , s. 2006 , , 131 , 1163	we present a catalog of 110 variable stars within of sgr a * based on image subtraction of near - infrared ( and ) photometry . we associate irs 10 * with oh , sio , and ho masers and a bright x - ray point source ; this analysis suggests irs 10 * is an agb star with an accreting companion . among the newly discovered sources are a probable cataclysmic variable , a potential edge - on contact 84 day period eclipsing binary , and a possible 41 day period pulsating variable	we present a catalog of 110 variable stars within of sgr a * based on image subtraction of near - infrared ( and ) photometry . our images were obtained over 133 nights from 2000 to 2002 in-band and over 134 nights from 2001 to 2002 in-band ; the typical fwhm is . we match the catalog to other near - infrared , x - ray , and radio ( i.e. , maser ) data , and we discuss some of the more interesting objects . the catalog includes 14 sources with measurable periods , several known long - period variables and three new lpv candidates . we associate irs 10 * with oh , sio , and ho masers and a bright x - ray point source ; this analysis suggests irs 10 * is an agb star with an accreting companion . among the newly discovered sources are a probable cataclysmic variable , a potential edge - on contact 84 day period eclipsing binary , and a possible 41 day period pulsating variable
astro-ph9808206	i	with the recent development of large format infrared array detectors , high quality photometric surveys are routinely conducted at wavelengths between 12.5 @xmath3 m . soon the completion of the 2 micron all sky survey ( 2mass ; skrutskie 1997 ) and denis ( epchtein et al . 1997 ) will provide comprehensive catalogues of near infrared sources with detection limits sensitive to a wide variety of stellar and non stellar objects . infrared spectra will be required for appropriate identification of many of these sources , and for further study of their astrophysical properties . the pioneering study of johnson and mendez ( 1970 ) was the first to explore the spectra of a large sample of normal stars in the near infrared . however many years passed before improvements in instrumentation made possible similar observations of large numbers of targets of astrophysical interest . the majority of the work done in near infrared spectroscopy to date has been focused on the k band , in large part because intrinsically cool or heavily obscured objects are typically brighter at k band than in the j or h bands . in 1986 , kleinmann and hall ( 1986 ; kh86 ) provided the first comprehensive medium resolution atlas ( @xmath4 ) of stellar spectra in the k - band , covering all luminosity classes , but restricted to spectral types between f8-m7 . more recently , wallace and hinkle ( 1997 ; wh97 ) have extended the kh96 k band atlas , using the same fts spectrograph on the kpno 4 m with @xmath4 , but including stellar spectra spanning spectral types o - m and luminosity classes i - v . they also summarize the considerable body of work directed toward k band spectroscopy in the last decade . while in many situations , the k band will be the wavelength selection of choice for spectroscopic studies of highly obscured or very cool objects , the presence of circumstellar dust ( @xmath5 ; pollack et al . 1994 ) often results in significant excess continuum emission longward of @xmath6 m . this continuum excess is commonly found in two important classes of objects : young stars with circumstellar disks ( e.g. meyer , calvet , & hillenbrand , 1997 ) and evolved stars with extensive envelopes from mass - loss ( e.g. le bertre 1997 ) . near infrared excess due to warm dust can also complicate spectroscopic studies of composite stellar systems aimed at discerning the stellar populations of other galaxies ( e.g. schinnerer et al . continuum excess longward of @xmath6 m will weaken or even render invisible the photospheric features in the k band , while the photosphere will dominate at shorter wavelengths . in such a situation , near infrared spectra shortward of 2 @xmath3 m will be required to see the stellar photosphere too obscured to be detected optically . to date , there has been relatively little work in the h band ( 1.551.75 @xmath3 m ) . recent publications include : i ) observations of 40 g , k , and m stars of luminosity class i and iii at @xmath7 by origlia , moorwood , and oliva ( 1993 ) ; ii ) the library of 56 spectra o m of luminosity class i , ii , and v at @xmath8 ( lancon & rocca volmerange , 1992 ) ; iii ) a library of 37 stars of luminosity classes i , iii , v at @xmath9 ( dallier , boisson , & joly 1996 ) over a limited portion of the h band ; and iv ) a study of 9 ob stars at @xmath10 ( blum et al . 1997 ) . here we present an h band spectral atlas for 85 stars of nearly solar abundance with spectral types on the mk classification system ranging from 07-m5 and luminosity classes i - v . these @xmath4 spectra were collected with the same fts at the kpno 4 m as the k band atlases of kh86 and wh97 . in section 2 , we describe the sample selection and in section 3 we describe the observations and calibration of the data . in section 4 we discuss the dependence of the spectral features on temperature and luminosity and suggest a two dimensional classification appropriate for late - type stars . in section 5 we discuss near ir spectral classification with regard to wavelength range / spectral resolution , and conclude with a summary of our results .	we present a catalogue of h band spectra for 85 stars of approximately solar abundance observed at a resolving power of 3000 with the kpno mayall 4 m fts . the atlas covers spectral types o7m5 and luminosity classes i - v as defined on the mk system . the line ratios permit spectral classification in the presence of continuum excess emission , which is commonly found in pre main sequence and evolved stars . we demonstrate that with spectra of obtained at it is possible to derive spectral types within subclasses for late type stars .	we present a catalogue of h band spectra for 85 stars of approximately solar abundance observed at a resolving power of 3000 with the kpno mayall 4 m fts . the atlas covers spectral types o7m5 and luminosity classes i - v as defined on the mk system . we identify both atomic and molecular indices and line ratios which are temperature and luminosity sensitive allowing spectral classification to be carried out in the h band . the line ratios permit spectral classification in the presence of continuum excess emission , which is commonly found in pre main sequence and evolved stars . we demonstrate that with spectra of obtained at it is possible to derive spectral types within subclasses for late type stars . these data are available electronically through the astronomical data center in addition to being served on the world wide web . # 1#2#3#4#5#6#7 to = -0.2 truein
1601.00243	i	fluid flows in two spatial dimensions have been the subject of substantial research efforts in recent decades . for the greater part of the twentieth century , it was generally considered that two - dimensional ( 2d ) flows were merely a theoretical idealization with limited practical relevance . this conception has changed drastically since the 1980s , when experiments in thin electrolyte layers @xcite , soap films @xcite , and liquid metals @xcite demonstrated that nearly 2d flows can indeed be realized in the laboratory . today , experimental approximations of 2d flows are widely employed as models of atmospheric and oceanic flows @xcite . being theoretically and experimentally more amenable than their three - dimensional ( 3d ) counterparts , 2d flows have also served as platforms for studying new phenomena such as turbulent cascades @xcite , coherent structures @xcite , and mixing @xcite . hence , experimental studies of 2d flows , with quantitative comparisons to theoretical predictions , are important for improving our understanding of fluid flows , in both 2d and 3d . perhaps one of the best known 2d fluid flow models is a flow introduced by andrey kolmogorov in 1959 as a mathematical problem for studying hydrodynamic stability @xcite . the kolmogorov flow represents the motion of a viscous fluid in two dimensions ( we will refer to these as @xmath0 and @xmath1 ) driven by a forcing that points along the @xmath0-direction and varies sinusoidally along the @xmath1-direction . the fluid flow is considered incompressible , @xmath2 , and is governed by the 2d navier - stokes equation , @xmath3 here , @xmath4 is the velocity field , @xmath5 is the 2d pressure field , and @xmath6 represents the driving force with amplitude @xmath7 and wavenumber @xmath8 . the parameters @xmath9 and @xmath10 are the density and the kinematic viscosity of the fluid , respectively . kolmogorov flow has served as a convenient model for understanding a wide variety of hydrodynamic phenomena in 2d , such as fluid instabilities @xcite , 2d turbulence @xcite , and coherent structures @xcite . practically realizable flows , however , are never strictly 2d . experimental approximations of kolmogorov flow have often been carried out in either shallow layers of electrolytes @xcite or in soap films @xcite , wherein geometric confinement suppresses the component of velocity along one of the spatial directions ( @xmath11 ) . the remaining two velocity components , however , generally depend on both extended and confined coordinates , making the flow `` quasi - two - dimensional '' ( q2d ) . to account for the dependence on the confined coordinate , q2d flows in shallow layers have often been modelled by adding a linear friction term to the 2d navier - stokes equation ( [ eq:2dns ] ) : @xmath12 where @xmath13 is a constant . the addition of this term was first suggested by @xcite to model a q2d flow generated in a homogeneous shallow electrolyte layer . in such a flow , the bottom of the fluid layer is constrained to be at rest because it is in contact with the solid surface of the container holding the fluid . this no - slip constraint at the bottom of the fluid layer causes a gradient in the magnitude of the horizontal velocity * u * along the confined direction @xmath11 . @xcite rationalized that the dissipation due to this shear , for sufficiently shallow fluid layers , is captured by the linear friction term . in the context of q2d flows in electrolyte layers , this term has come to be known as `` rayleigh friction . '' experimental flows in thin layers as well as models that employ equation ( [ eq:2dns_wf ] ) are now commonly referred to as `` kolmogorov - like , '' when the forcing profile is nearly sinusoidal . experimental realizations of q2d flows in recent years have employed two - fluid - layer setups : either a setup with _ miscible _ layers comprised of a heavy electrolyte fluid ( salt water ) beneath a lighter nonconducting fluid ( pure water ) @xcite , or a setup with _ immiscible _ layers comprised of a heavy dielectric fluid beneath a lighter electrolyte @xcite . the rationale behind these modifications was that in addition to confinement , density stratification and immiscibility should enhance two - dimensionality in the top layer . theoretical models of q2d experimental flows realized in stratified layers of fluids , however , have not accurately modelled the effect of the gradient in the magnitude of horizontal velocity @xmath14 along the confined direction @xmath11 . consequently , experiments were compared with simulations based on the 2d model ( [ eq:2dns_wf ] ) with empirically estimated parameters @xcite . to address this deficiency , @xcite have investigated the variation in the horizontal velocity @xmath14 along the confined direction @xmath11 for a stratified two - immiscible - layer setup . the following modified version of equation ( [ eq:2dns_wf ] ) which accounts for the inherent three - dimensionality of a q2d flow and describes its evolution quantitatively was proposed : @xmath15 where @xmath16 is a numerical prefactor to the advection term that was not accounted for previously . this prefactor reflects the decrease of the mean inertia of the fluid layer due to the variation of the horizontal velocity in the vertical direction . equation ( [ eq:2dns_mod ] ) has been derived from first principles by depth - averaging the full 3d navier - stokes equation under the q2d approximation ( cf . appendix [ sec : sensitivity ] ) . the coefficients @xmath13 , @xmath10 , and @xmath17 are estimated by including effects of both the inhomogeneity in fluid properties as well the vertical profile of @xmath14 along @xmath11 . equations ( [ eq:2dns ] ) and ( [ eq:2dns_wf ] ) can be treated as special cases of ( [ eq:2dns_mod ] ) with suitable choices of the parameters @xmath13 and @xmath17 . furthermore , equation ( [ eq:2dns_wf ] ) can also be obtained from ( [ eq:2dns_mod ] ) by rescaling the variables ( cf . appendix [ sec : nondim ] ) . in this article we study instabilities of a q2d kolmogorov - like flow realized in a setup with two immiscible fluid layers . we compare experiments with results from direct numerical simulations ( dns ) of equation ( [ eq:2dns_mod ] ) . most previous studies of kolmogorov - like flow compared experiments to theoretical analysis of a perfectly sinusoidal shear flow on unbounded or periodic domain @xcite . while some of these studies reported quantitative agreement between theory and experiment in regards to the primary instability , none where able to match simultaneously both the critical reynolds number and the critical wavenumber . even matching one of these required treating the rayleigh friction coefficient @xmath13 as an adjustable parameter . to address these difficulties , we systematically investigate the effects of lateral confinement , which was not properly addressed by the previous studies , using numerical simulations with three different sets of boundary conditions . furthermore , we investigate how the observed flow patterns and their stability are affected by the deviations in the forcing profile from perfect periodicity in the extended directions and by the variation of the forcing profile in the confined direction . finally , we compare the results of numerical simulations with the experimental observations for the secondary instability , which introduces time - dependence into the flow . the prospect of developing a 2d model that quantitatively describes the evolution of a q2d flow is particularly appealing in view of the recent theoretical advances in understanding transitional flows and weak turbulence as a dynamical process guided by nonchaotic , unstable solutions of the navier - stokes equation , often referred to as exact coherent structures ( ecs ) @xcite . the bulk of numerical studies have explored the role of ecs in 3d flows simulated on periodic domains with simple geometries , such as pipe flow , plane couette flow , and plane poiseuille flow . however , experimental evidence for the role of ecs is scarce @xcite , in part due to technical limitations in obtaining spatially and temporally resolved 3d velocity fields . q2d flows , on the other hand , can be quantified using 2d planar velocity fields which are relatively easy to measure . hence , experimental q2d flows that can be described by a 2d model serve as an ideal platform for testing and developing an ecs - based approach to understanding turbulence . recently , @xcite and @xcite have identified dozens of ecs in numerical simulations of a weakly turbulent 2d kolmogorov flow , governed by equation ( [ eq:2dns ] ) with periodic boundary conditions . we hope that this paper helps provide a rigorous foundation for future studies in the same spirit , but with a focus on experimental validation of theoretical predictions . this article is organized as follows . in [ sec : exp_setup ] , we describe the experimental setup employed to generate a q2d kolmogorov - like flow . in [ sec : model ] , we introduce a realistic model of the forcing in the experiment and discuss different types of lateral boundary conditions which are used to study the effects of confinement theoretically . in [ sec : comparison ] , we compare the flow fields obtained from experimental measurements with those from the numerical simulations for different flow regimes and characterize the bifurcations associated with increasing the forcing strength . conclusions are presented in [ sec : conclusion ] .	we also introduce a realistic numerical model approximating the electromagnetic body force in the experiment , which is validated against experimental measurements . we then explore the effect of lateral boundaries by performing direct numerical simulations ( dns ) subject to different types of boundary conditions . we compare the flow regimes observed in the experiment with those obtained from the dns and find that only the simulation subject to physical no - slip boundary conditions provides close , quantitative agreement . our analysis offers additional validation of the 2d model proposed by , as well as a demonstration of the importance of properly modelling the forcing and boundary conditions .	we present a combined experimental and numerical study of the primary and secondary instabilities in a kolmogorov - like flow . the experiment uses electromagnetic forcing with an approximately sinusoidal spatial profile to drive a quasi - two - dimensional ( q2d ) shear flow in a thin layer of electrolyte suspended on a thin lubricating layer of a dielectric fluid . the experimental flow is modelled using a recently proposed 2d equation , derived from first principles by depth - averaging the full three - dimensional navier - stokes equations . we also introduce a realistic numerical model approximating the electromagnetic body force in the experiment , which is validated against experimental measurements . we then explore the effect of lateral boundaries by performing direct numerical simulations ( dns ) subject to different types of boundary conditions . as the strength of the forcing is increased , this q2d flow undergoes a series of bifurcations . we compare the flow regimes observed in the experiment with those obtained from the dns and find that only the simulation subject to physical no - slip boundary conditions provides close , quantitative agreement . our analysis offers additional validation of the 2d model proposed by , as well as a demonstration of the importance of properly modelling the forcing and boundary conditions .
1601.00243	c	in this article , we have presented a combined experimental and numerical study of bifurcations in a q2d kolmogorov - like flow . this flow is realized in the laboratory by electromagnetically driving a stratified layer of electrolyte above an immiscible layer of dielectric . this q2d flow is described using a 2d model derived from first principles by depth - averaging the 3d navier - stokes equation . in contrast , virtually all previous studies have modelled q2d flows using equation ( [ eq:2dns_wf ] ) , a semi - empirical variation of the 2d navier - stokes equation with the addition of a linear friction . also unlike previous studies of kolmogorov - like flows which have assumed a perfectly sinusoidal forcing profile , we have introduced a realistic model of the forcing which has been validated against 3d experimental measurements . to test the importance of lateral confinement , we have compared experimental measurements with numerical simulations using different boundary conditions . we have found that by incorporating realistic , no - slip boundary conditions at all lateral boundaries and a realistic forcing profile , quantitative agreement between the experiment and simulation can be achieved with no adjustable parameters . in particular , the reynolds number @xmath153 for the primary instability can be predicted to within about 5% and the critical wavenumber @xmath178 can be predicted to an accuracy higher than the measurement accuracy . these are significant improvements compared with previous studies , none of which were able to predict both @xmath153 and @xmath178 with this level of accuracy , _ despite using adjustable parameters_. furthermore , we have demonstrated that the model reasonably accurately predicts the modulated flow pattern ( both the wavenumber and the amplitude ) beyond the onset of the primary instability . moreover , this is the first study , experimental or theoretical , to provide a quantitative analysis of the secondary instability of a kolmogorov - like flow which generates a time - dependent pattern of vortices . even for the secondary instability the numerical predictions of the critical reynolds number @xmath175 and the critical period @xmath176 are in general agreement with the experiment , although the accuracy of the numerical predictions decreases with increasing @xmath139 . the discrepancy between the numerical predictions and experiments has been traced back to two factors : ( 1 ) the dependence of the parameters of the 2d model on the average wavenumber of the flow pattern , which in turn depends on the reynolds number , and ( 2 ) the variation of the forcing profile with height . both of these issues point to the limitations of the 2d model of what in reality is a 3d flow , albeit with a strongly suppressed vertical component of the velocity . nonetheless , for a select range of @xmath139 the experimental flow can be reproduced with extremely good quantitative accuracy by making fairly small adjustments to the model parameters , compared with their depth - average values computed for a simple straight flow . the ability of the model to closely reproduce the experimental flow is crucial for the utility of q2d flows for testing the geometrical description of weakly turbulent flows and studying the dynamical role of exact coherent structures . such tests will be the main focus of a follow up study .	we present a combined experimental and numerical study of the primary and secondary instabilities in a kolmogorov - like flow . the experiment uses electromagnetic forcing with an approximately sinusoidal spatial profile to drive a quasi - two - dimensional ( q2d ) shear flow in a thin layer of electrolyte suspended on a thin lubricating layer of a dielectric fluid . the experimental flow is modelled using a recently proposed 2d equation , derived from first principles by depth - averaging the full three - dimensional navier - stokes equations .	we present a combined experimental and numerical study of the primary and secondary instabilities in a kolmogorov - like flow . the experiment uses electromagnetic forcing with an approximately sinusoidal spatial profile to drive a quasi - two - dimensional ( q2d ) shear flow in a thin layer of electrolyte suspended on a thin lubricating layer of a dielectric fluid . the experimental flow is modelled using a recently proposed 2d equation , derived from first principles by depth - averaging the full three - dimensional navier - stokes equations . we also introduce a realistic numerical model approximating the electromagnetic body force in the experiment , which is validated against experimental measurements . we then explore the effect of lateral boundaries by performing direct numerical simulations ( dns ) subject to different types of boundary conditions . as the strength of the forcing is increased , this q2d flow undergoes a series of bifurcations . we compare the flow regimes observed in the experiment with those obtained from the dns and find that only the simulation subject to physical no - slip boundary conditions provides close , quantitative agreement . our analysis offers additional validation of the 2d model proposed by , as well as a demonstration of the importance of properly modelling the forcing and boundary conditions .
1104.0656	i	the rapid development of quantum information science has brought together several areas of theoretical and experimental physics @xcite . much effort has been concentrated in the search for solutions to sensitive problems that prevent the efficient realization of quantum information processing @xcite . we first mention the system - environment coupling which induces the decoherence of quantum states @xcite , apart from other barriers such as scalability @xcite and optimal control of individual systems @xcite . these challenges motivate both fundamental physical phenomena and outstanding technological issues such as individually addressing quantum systems , separated by only few @xmath3 m , with small errors @xcite . potential platforms for the implementation of quantum logic operations appeared in many fields such as condensed matter , quantum optics , and atomic physics @xcite . however , the problems mentioned above are faced by all the different communities when employing their particular techniques . in the particular case of the dissipation and decoherence phenomena in which we focus in the present work the redfield formalism redfield , slichter and the master equation @xcite have been the most applied approaches to address the environment effects on the proposed protocols for quantum information processing . whereas the semiclassical redfield formalism relies on a classical noise source , a quantum environment is assumed in the master equation approach . in this article , considering the general case of a time - dependent system , we discuss general similarities and differences between both approaches and show that they are equivalent , in the sense that they lead to the same phenomenological bloch equations bloch . consequently , both of them result in the same characteristic relaxation times @xmath1 and @xmath2 associated with the longitudinal and transverse relaxations , respectively @xcite . from this identification we show how these characteristic times are related to the operator - sum representation @xcite and the phenomenological - operator approach @xcite . the redfield formalism was intended to offer a microscopic description of the relaxation phenomenon , thus providing a deeper understanding of the parameters @xmath1 and @xmath2 . whereas the classical noise source employed in the redfield theory suffices to derive both relaxation times , two distinct quantum environments must be adopted to derive these time scales from the master equation formalism . on this regard , an amplitude and a phase damping environment are assumed to define the longitudinal and the transverse relaxation times , respectively . these quantum environments represent an energy - draining and a phase - shuffle channel by which the system loses excitations and phase relations . after presenting a detailed derivation of the redfield theory and comparing the derived characteristics times with those obtained from the master equation , we finally apply these equivalent formulations to the problem of state protection . we note that several distinct techniques have been proposed to control the effects of decoherence on quantum states , aiming to enlarge the fidelity of quantum information protocols . among others , we mention the quantum - error correction codes @xcite , environments engineering @xcite , decoherence - free subspaces @xcite , and dynamical decoupling @xcite . we finally mention that in a previous work @xcite , addressing the energy draining and decoherence of a harmonic oscillator , it was demonstrated that the inevitable action of the environment can be substantially weakened when considering appropriate non - stationary quantum systems . reasoning by analogy with the technique presented in ref . lucas , we show how to enlarge the longitudinal relaxation time associated with the amplitude - damping channel focusing a spin-@xmath0 system . the ideas presented here for decoherence control can be easily implemented in the nuclear magnetic resonance ( nmr ) context . this article is organized as follows : in sec . ii we present the derivation of the redfield equation for the general scenario of a time - dependent system . in sec . iii we apply the master equation approach to the same case . in sec . iv we show the equivalence between the redfield and the master equation formalisms by deriving the bloch equations from both approaches . focusing on a time - dependent spin-@xmath0 system , in secs . v and vi we present the operator - sum representation and the phenomenological operator approaches and their relation with the previous techniques . as an application of the theory , in sec . vii we address the state protection of a non - stationary spin-@xmath0 system . finally , sec . viii is dedicated to our final remarks where we discuss the generalization of the methods presented in this article for larger systems . in general , we will adopt the language of the nmr quantum information processing @xcite , although the theory presented here is valid for several other platforms , as quantum dots @xcite , superconducting artificial atoms @xcite , etc . throughout the article we will use natural units such that @xmath4 .	we present a derivation of the redfield formalism for treating the dissipative dynamics of a time - dependent quantum system coupled to a classical environment . we compare such a formalism with the master equation approach where the environments are treated quantum mechanically . focusing on a time - dependent spin- system these characteristic times are shown to be related to the operator - sum representation and the equivalent phenomenological - operator approach .	we present a derivation of the redfield formalism for treating the dissipative dynamics of a time - dependent quantum system coupled to a classical environment . we compare such a formalism with the master equation approach where the environments are treated quantum mechanically . focusing on a time - dependent spin- system we demonstrate the equivalence between both approaches by showing that they lead to the same bloch equations and , as a consequence , to the same characteristic times and ( associated with the longitudinal and transverse relaxations , respectively ) . these characteristic times are shown to be related to the operator - sum representation and the equivalent phenomenological - operator approach . finally , we present a protocol to circumvent the decoherence processes due to the loss of energy ( and thus , associated with ) . to this end , we simply associate the time - dependence of the quantum system to an easily achieved modulated frequency . a possible implementation of the protocol is also proposed in the context of nuclear magnetic resonance .
cond-mat9411034	c	in this paper we presented a detailed , quantitative study of the physical effects caused by the simultaneous presence of interactions and randomness in a system of lattice electrons . to this end we investigated the anderson - hubbard model with diagonal disorder at half filling in the limit of infinite spatial dimensions , i.e. within a dynamical mean - field theory , for three different disorder distributions . numerical results were obtained by employing quantum monte carlo techniques that provide an explicit finite - temperature solution of the model in @xmath9 . no further approximation were used . to construct the thermodynamic phase diagram we derived and evaluated the appropriate averaged two - particle correlation function , i.e. a dynamical response function , whose poles determine the magnetic instabilities of the disordered , interacting system . only this function and not the averaged staggered susceptibility @xmath144 itself , which is only a weighted sum of the response function over the ( matsubara ) frequencies fulfills a closed equation that determines the two - particle spectrum . the value of the response function at the lowest frequency is the most sensitive indicator for an instability of the system . in the temperature dependence of @xmath144 two distinct disorder regimes are observed : ( i ) for weak disorder the curie - weiss law holds , while ( ii ) at strong disorder @xmath144 acquires a maximum at a temperature below which a crossover from the temperature- to the disorder- dominated regime takes place . we demonstrated that at low temperatures and sufficiently strong interaction there always exists a phase with antiferromagnetic long - range order ( aflro ) . furthermore we discovered a new strong - coupling anomaly , namely that the nel - temperature @xmath194 is not always a monotonously decreasing function of disorder . indeed , at strong coupling and not too large disorder @xmath194 is always found to be an _ increasing _ function of disorder , i.e. disorder favors the formation of aflro in this regime . this implies the existence of an unexpected _ disorder - induced _ transition to a phase with aflro . under the assumption that @xmath194 is proportional to the effective exchange coupling between spins even in the disordered system we proved that for diagonal disorder the anomalous behavior is generic , i.e. is independent of the type of disorder distribution . it is a consequence of the fact that for diagonal disorder the difference between the local energies of neighboring sites becomes _ smaller _ on average , thus leading to stronger effective exchange coupling . we then studied the existence of metal - insulator transitions in the anderson - hubbard model . although in @xmath9 anderson localization does not take place the presence of disorder may well have other strong effects . in particular , binary - alloy disorder is able to cause band - splitting ( thereby resembling the effect of genuine interactions ) and hence may induce a metal - insulator transition all by itself . special attention was given to the question whether or not the disorder allows for the stabilization of an antiferromagnetic ( af ) _ metal_. to this end the average compressibility @xmath96 was evaluated both in the paramagnetic ( p ) and af phase . contrary to our expectation the presence of disorder was found to enhance the metallicity of the af - phase close to the p - af transition . this enhancement strongly suggests the existence of an af metal in the low - temperature phase of the anderson - hubbard mode . to investigate whether this af phase persists to be metallic down to @xmath320 , at least in @xmath9 , we studied the frequency components of the one - particle green function and of @xmath96 , respectively , down to @xmath290 , our lowest temperature . however , a reliable answer to this question can only be found at still lower temperatures , which at present are beyond the reach of the finite - temperature monte carlo techniques used here . in any case , the transition scenario involving metal - insulator and p - af transitions obtained for the anderson - hubbard model is remarkably rich . for alloy - type disorder with @xmath265 ( split - band limit for @xmath324 ) at @xmath320 an increase of the interaction @xmath57 from zero will probably first lead to a transition from a paramagnetic insulator to a paramagnetic metal at @xmath266 , then , at @xmath277 , to an antiferromagnetic metal and finally , at @xmath270 , to an antiferromagnetic insulator . no compelling evidence was found that @xmath277 and @xmath270 coincide . in the case of a continuous disorder distribution one has @xmath267 since band splitting never occurs . the above findings prove that the interplay between electronic interactions and scattering from disorder leads to interesting , and even novel , physical effects . in particular , the strong coupling anomaly discovered here call for an experimental verification . we are grateful to a. altland , p. van dongen , m. jarrell , h. mller - krumbhaar and especially e. mller - hartmann for very useful discussions and comments . this work was supported in part by the sonderforschungsbereich 341 of the deutsche forschungsgemeinschaft . in fact in their exact solution of the falicov - kimball model in @xmath9 brandt and mielsch [ z. phys . * b75 * , 365 , ( 1989 ) ; ibid . * b79 * , 295 ( 1990 ) ; ibid * b82 * , 37 ( 1991 ) ] were the first to show that the local self - energy may be used to map the lattice problem in @xmath9 onto its atomic counterpart with an additional `` kadanoff - baym field '' which has to be determined self - consistently ; for an application to other hubbard - like models see g. hlsenbeck and f. stephan ( preprint ) . x. y. zhang , m. j. rozenberg and g. kotliar , phys . lett . * 70 * , 1666 ( 1993 ) ; m. j. rozenberg , g. kotliar and x.y . zhang , phys . rev . * b49 * , 10181 ( 1994 ) ; q. si , m.j . rozenberg , g. kotliar , and a. e. ruckenstein , preprint . in principle the grand potential ( 6 ) may equally be viewed as a functional of the set of complex functions @xmath48 _ only _ in which case , however , one has to _ supplement _ ( 6 ) by the definition of @xmath47 as the local ( i.e. site - diagonal ) element of the full temperature green function ( see below ) . in the initial formulation of the theory it is advisable to treat _ both _ set of legendre - conjugate variables @xmath48 and @xmath47 as variational parameters , since only then does the expression ( 6 ) contain the full information about the thermodynamic equilibrium of the system @xcite . an equilibrium corresponds to a saddle point where the variations of @xmath51 w.r.t . @xmath48 and @xmath47 vanish , i.e. @xmath325 and @xmath326 . these variational conditions determine the physical values of @xmath47 and @xmath48 as the local green function and self - energy of the electrons , respectively . a theory generated in this way is guaranteed to be thermodynamically consistent and conserving in the spirit of the baym - kadanoff formalism [ g. baym , phys . rev . * 127 * , 836 ( 1962 ) ] . fig.1 : : local green function @xmath160 for @xmath324 and @xmath328 ( a ) , @xmath329 ( b ) obtained by usual fourier transformation ( dotted line ) and by redefinition acc . to eq.(13 ) ( solid line ) fig.2 : : dynamical antiferromagnetic response function @xmath185 vs. temperature @xmath330 . binary alloy with disorder strength @xmath331 and @xmath332 . here and in the following figures lines are usually guides for the eye , and error - bars are roughly of the size of the symbols unless shown explicitly . fig.3 : : inverse averaged antiferromagnetic susceptibility @xmath333 vs. @xmath330 for the binary alloy with @xmath334 and several values of @xmath57 . fig.4a : : @xmath202-phase diagram for the binary alloy with @xmath335 obtained from the zeroes of @xmath333 ( see fig . 4 ) . the af - phase is stable below the curves . the dotted lines at @xmath320 depict the regimes where the curie law would give negative transition temperatures . below the crosses @xmath333 has no zeroes but a minimum and an af - phase can no longer be expected . fig.4b : : @xmath202-phase diagram for the semi - elliptic distribution of the random energies with width @xmath336 . fig.5 : : @xmath330 vs. @xmath227 for the binary - alloy distribution at @xmath337 and 5.5 . dashed lines : quadratic increase of @xmath194 according to eq . ( 30b ) with @xmath338 ; dotted lines are guides to the eye only . fig.6 : : scaling plot of @xmath339 for the binary - alloy distribution according to eq . ( 30 ) ; symbols as in fig . 4a . fig.7 : : @xmath340-phase diagram for the percolation - type disorder for several values of @xmath57 . the dashed line depicts the hartree - fock ( hf ) result for the smallest value of @xmath341 . fig.8a : : averaged quadratic local moment @xmath239 vs. u at inverse temperature @xmath342 . without disorder ( full circle ) ; binary alloy with @xmath334 ( full square ) ; semi - elliptic distribution with @xmath334 ( open circle ) and @xmath343 ( open square ) . fig.8b : : averaged quadratic local moment @xmath344 ( normalized to the concentration of sites with random energy zero ) vs. @xmath99 for the percolation - type disorder at @xmath342 for several values of @xmath57 . fig.9 : : staggered magnetization @xmath249 and inverse averaged susceptibility @xmath333 vs. @xmath330 for the binary alloy with @xmath331 , @xmath332 , @xmath345 . dashed line : square - root fit of the last two points of @xmath249 below the transition ; dotted line : linear fit of @xmath333 . the arrow indicates the extrapolated nel temperature . fig.10 : : averaged compressibility @xmath96 vs. @xmath57 at @xmath342 . a ) binary alloy , @xmath335 ; b ) semi - elliptic distribution with @xmath346 and 4 . arrows indicate the transition to the antiferromagnetic state . fig.11 : : averaged compressibility @xmath96 vs. @xmath57 at @xmath342 in the paramagnetic phase ( dashed lines ) and in the antiferromagnetic phase ( dotted lines ) . a ) binary alloy , b ) semi - elliptic distribution . fig.12 : : averaged compressibility @xmath96 vs. @xmath57 for the binary alloy at @xmath342 and 40 . arrows indicate the transition to the antiferromagnetic state . fig.13 : : real part of @xmath347 vs. @xmath45 , a ) for @xmath348 , @xmath349 and @xmath350 in the paramagnetic phase ( p ) and the antiferromagnetic phase ( af ) ; b ) for the binary alloy with @xmath334 , @xmath351 in the af - phase at @xmath352 and 64 . fig.14 : : imaginary part of the one - particle green function @xmath161 at the lowest matsubara frequency @xmath353 vs. @xmath57 for a system without disorder ( @xmath279 ) and with binary - alloy disorder ( @xmath280 at @xmath342 ; p - phase ( dashed lines ) , af - phase ( dotted lines ) . fig.15 : : imaginary part of @xmath161 vs. @xmath45 in the p- and af - phase ; a ) no disorder , u=1.75 , @xmath350 ; b ) binary alloy with @xmath334 , @xmath351 , @xmath354 ( the two curves at @xmath355 in the middle are undistinguishable ) . fig.16 : : imaginary part of @xmath356 vs. @xmath330 for the binary alloy with @xmath334 for several values of @xmath57 .	we present a detailed , quantitative study of the competition between interaction- and disorder - induced effects in electronic systems . for this the anderson - hubbard model with diagonal disorder is investigated analytically and numerically in the limit of infinite spatial dimensions , i.e. within a dynamical mean - field theory , at half filling . numerical results are obtained for three different disorder distributions by employing quantum monte carlo techniques which provide an explicit finite - temperature solution of the model in this limit . the magnetic phase diagram is constructed from the zeros of the inverse averaged staggered susceptibility . we find that at low enough temperatures and sufficiently strong interaction there always exists a phase with antiferromagnetic long - range order . the existence of metal - insulator transitions is studied by evaluating the averaged compressibility both in the paramagnetic and antiferromagnetic phase . a rich transition scenario , involving metal - insulator and magnetic transitions , is found and its dependence on the choice of the disorder distribution is discussed .	we present a detailed , quantitative study of the competition between interaction- and disorder - induced effects in electronic systems . for this the anderson - hubbard model with diagonal disorder is investigated analytically and numerically in the limit of infinite spatial dimensions , i.e. within a dynamical mean - field theory , at half filling . numerical results are obtained for three different disorder distributions by employing quantum monte carlo techniques which provide an explicit finite - temperature solution of the model in this limit . the magnetic phase diagram is constructed from the zeros of the inverse averaged staggered susceptibility . we find that at low enough temperatures and sufficiently strong interaction there always exists a phase with antiferromagnetic long - range order . a novel strong coupling anomaly , i.e. an _ increase _ of the nel - temperature for increasing disorder , is discovered . an explicit explanation is given which shows that in the case of diagonal disorder this is a generic effect . the existence of metal - insulator transitions is studied by evaluating the averaged compressibility both in the paramagnetic and antiferromagnetic phase . a rich transition scenario , involving metal - insulator and magnetic transitions , is found and its dependence on the choice of the disorder distribution is discussed .
astro-ph0506121	r	as the dynamical evolution calculations begins , the disks experience an initial transient , which is essentially numerical in origin , and is due to the fact that the configuration is not in strict hydrostatic equilibrium ( recall that it is obtained from azimuthally averaging the results of 3d calculations ) . this transient , and its effects , are negligible , and it is essentially over in a hydrodynamical timescale ( @xmath106 ms ) . after that , the disk proceeds to evolve on a much longer timescale , determined by accretion onto the central black hole . we first present the details of the spatial structure of the disk due to fundamental physical effects , and then proceed to show the temporal evolution and associated transitions . the fundamental variable affecting the instantaneous spatial structure of the disk is the optical depth to neutrinos , @xmath107 , since it determines whether the fluid cools efficiently or not . all quantities show a radical change in behavior as the threshold @xmath108 is passed . figure [ compa0.01t100 ] shows color coded contours in a meridional slice of the thermodynamical variables , while figure [ compa0.01t100r ] displays the run of density and entropy per baryon along the equator , @xmath109 , where the density and temperature are highest ( we will refer here mainly to run a2 m , unless noted otherwise ) . the density increases as one approaches the black hole , varying as @xmath110 in the outer regions , where @xmath111 . the critical density for opaqueness is reached at @xmath112 cm , and for @xmath113 , @xmath114 . since the energy that would otherwise be lost via neutrino emission remains in the disk if the cooling is suppressed by scattering , the density does not rise as fast . in fact , one can note this change also by inspecting the scale height @xmath115 , which scales as @xmath116 for @xmath117 and @xmath118 const for @xmath113 ( and thus in terms of surface density the change is from @xmath119 to @xmath120 const at @xmath121 ) . the opaque region of the disk remains inflated to a certain extent , trapping the internal energy it holds and releasing it only on a diffusion timescale . at densities @xmath122 g @xmath10 the optical depth can reach @xmath123 , and thus the suppression of cooling is dramatic , as can be seen in figure [ compa0.01t100 ] , where the contours of @xmath107 and @xmath124 are shown . the flattening of the entropy profile is related to the change in composition in the optically thick region and the occurrence of convection ( see [ nuconvection ] below ) . as the density rises in the inner regions of the disk , the electron fraction @xmath28 initially drops as neutronization becomes more important , with the equilibrium composition being determined by the equality of electron and positron captures onto free neutrons and protons ( see equation ( [ yethin ] ) and the discussion preceding it ) . the lowest value is reached at @xmath125 , where @xmath126 . thereafter it rises again , reaching @xmath127 close to the horizon . thus flows that are optically thin everywhere will reach a higher degree of neutronization close to the black hole than those which experience a transition to the opaque regime . the numerical values for the electron fraction at the transition radius and at the inner boundary are largely insensitive to @xmath5 , as long as the transition does occur . the baryons in the disk are essentially in the form of free neutrons and protons , except at very large radii and low densities ( @xmath128 cm and @xmath129 g @xmath10 ) where @xmath5 particles form . figure [ rtye ] shows the region in the density temperature plane where the fluid lies , for runs a2 m and a1 m at two different times ( and color coded according to the electron fraction ) . most of the gas lies close to the line determining the formation of helium nuclei ( see equation [ nuc ] ) , but does not cross over to lower temperatures . the reason for this is that the energy that would be released by the creation of one helium nucleus ( 28.3 mev ) would not leave the disk ( recall that we consider neutrino emission as the only source of cooling ) and thus immediately lead to the photodisintegration of another @xmath5 particle . an equilibrium is thus maintained in which the gas is close to helium synthesis , but this does not occur . in the opaque regime , the gas moves substantially farther from the transition line to helium , since it can not cool efficiently and , as mentioned before , the density does not rise as quickly . figure [ rtye ] also shows clearly why one must make use of an equation of state which takes into account properly the effects of arbitrary degeneracy of the electrons and positrons . the solid straight line marks the degeneracy temperature as a function of density , given by @xmath130 mev . the disk straddles this line , with a degeneracy parameter @xmath131 in the inner regions , and @xmath132 at lower densities . thus making the approximation that the electrons in the flow are fully degenerate is not accurate . modeling the accretion flow in two dimensions @xmath101 , without the assumption of equatorial symmetry allows one to solve clearly for the vertical motions in the disk , something which is not possible when considering vertically integrated flows . it was pointed out by @xcite that a standard @xmath5 viscosity could lead to meridional flows in which @xmath133 changed sign as a function of height above the mid plane , leading to inflows as well as outflows . @xcite , @xcite and @xcite later considered a similar situation , and found that for a range of values in @xmath5 , the gas flowed inward along the surface of the disk , and outward in the equatorial regions . in previous work @xcite , we found this solution in disk flow , with large scale circulations exhibiting inflows and outflows for high viscosities ( @xmath134 ) , and small scale eddies at lower values ( @xmath135 ) . how vertical motions affect the stability of accretion disks and may lead to the transport of angular momentum is a question that has become of relevance in this context @xcite . here we show in figure [ velcont ] the velocity field and magnitude of meridional velocity for run a2 m . the small scale eddies are clearly visible , with their strength usually diminishing as the disk is drained of matter and the density drops . the effect of a different value of @xmath5 can be seen in the top row of figure [ compa0.01a00.1t100t200 ] , where the comparison between @xmath136 and @xmath137 is made . the large , coherent lines of flow aimed directly at the origin for @xmath136 correspond to inflow , while the lighter shades along the equator at larger radii show outflowing gas . the instantaneous structure of the disk concerning the density , temperature and composition profiles is largely independent of the viscosity , as long as there is enough mass to produce the optically thin / optically thick transition . even in the optically thin regime , the structure can not be determined analytically following the standard arguments applied to thin , cool disks of the shakura sunyaev type . the reason for this is the following : a central assumption in the standard solution is that the disk is cool , i.e. , @xmath138 . this comes from the requirement that all the energy dissipated by viscosity , @xmath139 be radiated away efficiently , and produce the observed flux , @xmath140 . in our case , the disk is most certainly not cool , as it originates from the tidal disruption of a neutron star by a black hole ( or possibly the coalescence of two neutron stars , and subsequent collapse of the central mass to a black hole ) . the gas that constitutes the disk is dynamically hot because it was in hydrostatic equilibrium in a self gravitating configuration , where @xmath141 and has not been able to release this internal energy ( the merger process itself may lead to additional heating ) . a further deviation from the standard solution is that the pressure support in the disk leads to a rotation curve that is slightly sub keplerian . the dissipation by viscosity is in fact smaller than the cooling rate over much of the disk , and the released luminosity comes from a combination of viscous dissipation and the store of internal energy given to the disk at its conception . the classical requirement for convective instability in the presence of entropy and composition gradients , as well as rotation , is the solberg hoiland criterion @xcite : @xmath142 where @xmath143 is the radial epicyclic frequency ( @xmath144 being the angular velocity ) , and @xmath145 \label{bv}\ ] ] is the brunt visla frequency ( see * ? ? ? * ; * ? ? ? the adiabatic index @xmath146 in our case , since @xmath147 is the most important contribution to the total pressure . thus a region may be convectively unstable because of a composition gradient , or an entropy gradient , or both . strictly speaking , here one should consider the total lepton fraction @xmath148 . we do not consider the transport of neutrinos in detail , as already mentioned ( see [ nuopacities ] ) , and do not calculate explicitly the contribution of neutrinos to this @xmath148 . for what follows , we will thus simply take @xmath28 to represent the behavior of the full @xmath148 . the origin of convection in the lepton inversion zone can be understood as follows @xcite . consider a fluid element in the lepton inversion zone that is displaced in the outward direction and then comes to pressure equilibrium with its surroundings . the displaced element , which is lepton rich relative to its new surroundings , attains the ambient pressure at a lower density than the surrounding fluid , because the pressure depends directly on the lepton number , and thus tends to drift outwards . by the same token , an inwardly displaced fluid element in the lepton inversion zone is depleted in leptons relative to its new surroundings and thus tends to sink . when temperature gradients are allowed for , the displaced fluids , in general , have temperatures which differ from those of their surroundings . these variations tend to promote stability or instability depending on whether the existing temperature gradient is less than or greater than the adiabatic gradient , respectively . in the present scenario then , the transition to the optically thick regime leads to instability , because initially @xmath149 , and also @xmath150 ( see also figure [ compa0.01t100r ] ) . the entropy profile is then flattened by efficient convective mixing , and the lepton gradient inversion is due to the different way in which the composition is determined through weak interactions once the neutrinos become trapped . in a dynamical situation such as the one treated here , convection tends to erase the gradients which give rise to it . accordingly , the sum of the corresponding terms in equation ( [ sh ] ) tends to zero once the simulation has progressed and convection has become established in the inner disk ( note that in our case the rotation curve there is sub keplerian , with @xmath151 , so that @xmath144 and @xmath152 are not equal ) . this is analogous to what occurs in proto neutron stars following core collapse @xcite and has actually been confirmed in numerical simulations of such systems @xcite , where the convection leads to strong mixing . for a neutrino driven convective luminosity @xmath153 at radius @xmath154 and density @xmath155 , the convective velocity may be estimated by standard mixing length theory as ( see e.g. , * ? ? ? * ) @xmath156 where we have used the fact that gas pressure dominates in the fluid . the assumption of spherical symmetry implicit in this expression is not strictly met in our case , but it may provide us nevertheless with a useful guide . the overturn time of a convective cell is then given by @xmath157 ms , where @xmath158 km is the mixing length , usually set to a pressure scale height . in our calculations , we see that the magnitude of the meridional velocity @xmath159 decreases as @xmath4 decreases , then rises again as the opaque region is reached , reaching @xmath160 cm s@xmath8 , at @xmath161 km . the associated turnover times are thus @xmath162 ms , in good agreement with the estimate made above . to isolate this effect from that due to viscosity ( which generates the meridional circulations mentioned previously ) we have performed a simulation in which @xmath163 ( run aim in table [ table : ics ] ) . this calculation shows essentially no accretion onto the black hole except for a small amount of gas transferred at early times ( because the initial condition is not in strict equilibrium ) . the result concerning the profile of @xmath28 as a function of radius is as we have described above , i.e. , increasing neutronization as @xmath4 decreases , until the opaque region is reached , followed by an increase in @xmath28 as the black hole boundary is approached . the revealing difference lies in the time evolution of this profile . as mentioned above , convection generates motions which tend to eliminate the composition gradient which drives it . in the presence of viscosity , matter is continuously transported radially , and the gradient is not erased entirely . height integrated profiles of @xmath164 at 50 ms and 200 ms show a similar behavior at small radii . when viscosity is removed , the initial composition gradient is gradually softened until it disappears in the innermost regions ( see figure [ convection ] ) . the disk then has a nearly constant electron fraction along the equator for @xmath113 , with a sharp transition region leading to an increase with radius in the transparent regime . this may resemble the convection dominated accretion solution found analytically by @xcite and numerically by several groups @xcite , where convection transports angular momentum inward , energy outward , and gives a radial profile in density @xmath165 . we find a different power law , with @xmath114 . there are several factors which may account for this difference : the disk vs. spherical geometry ; the initial condition with a large amount of internal energy ; and the limited , but present cooling rate on the boundaries of the flow . since the neutrinos are diffusing out of the fluid ( the mean free path is small compared to the size of the system in the optically thick regime ) , one would expect a corresponding viscosity through @xmath166 ( see , e.g. * ? ? ? this needs to be compared to the corresponding viscosity generated by the assumed @xmath5 prescription for consistency . we may assume @xmath167 , where @xmath168 is the energy density associated with neutrinos , and @xmath169 is their mean free path ( see [ nuopacities ] ) . thus @xmath170 for conditions near the equatorial plane , @xmath109 . this value will increase in the outer regions , since the mean free path becomes larger as the density drops . at the neutrino surface , where @xmath171 , the mean free path is @xmath172 cm , and so an averaged value of the viscosity over the entire neutrino opaque region will result in an increase of about one order of magnitude over the estimate given in equation ( [ nuvisc ] ) ( note however , that strictly speaking the diffusion approximation is no longer valid in the outer regions , so this must be interpreted with care ) . for the @xmath5 prescription , @xmath173 . the rotation curve is not too far from keplerian , and scaling this expression to typical values we find @xmath174 the effects on angular momentum transport are thus a full two orders of magnitude below those arising from our viscosity prescription ( for @xmath175 ) . to put it another way , a lower limit for the viscosity under these conditions ( and in the optically thick portion of the disk ) would be @xmath176 . an alternative analysis would be to consider the corresponding timescales induced by this viscosity . since @xmath177 , smaller viscosities imply longer timescales , as expected . aside from convection , several general criteria for stability can be analyzed in our case . evidently , since we are performing dynamical calculations , any instability that arises will quickly lead to a change in structure . it is nevertheless instructive to consider the corresponding conditions within the disk . we first consider the toomre criterion , comparing gravitational and internal energies , with @xmath178 where @xmath152 is the local epicyclic frequency ( essentially equal in this case to the angular frequency @xmath144 ) , @xmath179 is the local sound speed and @xmath180 is the surface density . we find @xmath181 in all cases throughout the calculations , and thus that the disks are stable in this respect ( figure [ qthermalstability]a shows a typical profile of @xmath182 $ ] ) . previous studies @xcite have shown that neutrino cooled disks are thermally unstable if radiation pressure dominates in the flow , and stable otherwise , although the effects of neutrino opacities were not considered . the criterion for stability can be written in this case as @xmath183 where @xmath184 and @xmath185 are the volume heating and cooling rates . essentially , in order to be stable the disk must be able to get rid of any excess internal energy generated by an increase in the heating rate . we show in figure [ qthermalstability]b typical values for @xmath184 and @xmath185 as functions of the central ( equatorial ) temperature , for run a2 m at @xmath186 ms . in the optically thin region the disks are thermally stable , because the pressure is dominated by the contribution from free nucleons and cooling is efficient . in the optically thick region the cooling is greatly suppressed and the criterion would indicate that the disk becomes thermally unstable . this is reasonable , since with optical depths @xmath187 , essentially no direct cooling takes place , and dissipation is not suppressed . this is why the disk is geometrically thick in the inner regions , as already described above ( [ structure ] ) . the balance that gives a quasi steady state structure is achieved mainly through the diffusion of neutrinos , since the diffusion timescale is shorter than the accretion timescale . the evolution of the disk on long timescales is determined by the balance between two competing effects : on one hand , viscosity transports angular momentum outwards , matter accretes and the disk drains into the black hole on an accretion timescale @xmath188 . the trend in this respect is towards lower densities and temperatures . on the other hand , cooling reduces pressure support and leads to vertical compression , increasing the density . the internal energy of the fluid is released on a cooling timescale , @xmath189 . the presence of an optically thick region in the center of the disk limits the luminosity ( dominated by electron and positron capture onto free nucleons ) to @xmath190erg s@xmath8 , and the initial internal energy is @xmath191 erg , so @xmath192 s. if @xmath193 , the disk will cool before its mass or internal energy reservoir is significantly affected by accretion onto the black hole . the maximum density ( shown in figure [ rhomax ] for runs a1 m , a2 m and a3 m ) actually increases slightly due to vertical compression , and subsequently drops once mass loss through accretion dominates ( the @xmath194 ms delay at the start , during which it is approximately constant , is simply the sound crossing time across the optically thick region of the disk ) . the accretion rate onto the black hole , @xmath195 , the accretion timescale @xmath196 and the total neutrino luminosity @xmath197 are shown in figures [ mdot ] , [ tacc ] and [ lum ] . they all show the same qualitative behavior , remaining fairly constant ( or changing slowly ) for an accretion timescale , and abruptly switching thereafter . the accretion timescales are approximately 0.5 s and 5 s for @xmath198 respectively . for high viscosity , @xmath136 , the transport of angular momentum is vigorous , and the black hole quickly accretes a substantial amount of mass ( @xmath199 within the first 100 ms ) . the accretion timescale is @xmath200 ms . the circulation pattern consists of large scale eddies , with @xmath6 . in fact there is essentially one large eddy on each side of the equatorial plane , with mass inflow along the surface of the disk , and an equatorial outflow . part of the outflowing gas moves away from the equator and reverses direction close to the surface of the disk , contributing to the inflow . for an intermediate viscosity , @xmath137 , the intensity of the circulations is smaller , but also , the eddies are smaller , with several of them clearly occurring in the disk at once . the transport of angular momentum being less vigorous , the accretion rate is substantially smaller than in the previous case . finally , for a yet lower viscosity , @xmath201 , the trend continues , and the eddies become smaller still . in these last two cases , angular momentum transport is so low that very high densities are maintained in the central regions of the disk for a large number of dynamical times , contrary to what is seen in the high viscosity case . a simple way to quantify how much of the mass flow is actually making it to the central black hole is to measure the fraction of mass at any given radius that is moving inwards , @xmath202 , where we have divided the mass flow rate into two height integrated parts , one with @xmath203 and another with @xmath204 . for example , for run a2 m at @xmath205 ms and @xmath206 it is approximately 1/3 . the ratio tends to unity only in the innermost regions of the disk , and shows the true black hole mass accretion rate , plotted in figure [ mdot ] for the same cases . we now turn our attention to the neutrinos , which are the main source of cooling . the results in this case are markedly different from what we initially found @xcite , simply because of the new equation of state , the more realistic cooling rates and the approximate computation of opacities . they are in general agreement with the preliminary results we presented before @xcite , which used a less detailed equation of state than the one shown here . the optically thick region is present in every disk at the start of the calculation . as already mentioned , this has two important effects : enhancing the pressure and suppressing the neutrino emission . this reflects upon the total luminosity , since the suppression occurs precisely in the hottest regions , where most of the energy would otherwise be released . the most important qualitative difference between the runs presented here is that for a high viscosity ( @xmath136 , runs a1 m and a1 m ) , the disk is drained of mass so fast that it has no chance to cool ( @xmath207 ) and release most of its internal energy . it is in fact advected into the black hole . moreover , the optically thick region disappears entirely from the disk ( see figure [ compa0.01a00.1t100t200 ] ) by @xmath208 ms . the emission is then no longer suppressed ( see the contours of @xmath124 in the same figure ) , and the disk radiates at the maximum possible cooling rate . the thermal energy content of the disk is so large , that as it thins , the luminosity actually increases briefly around @xmath209 ms before dropping again . the drop at late times follows an approximate power law , with @xmath210 . in this interval the energy release comes from a combination of residual internal energy and viscous dissipation within the disk . for lower values of the viscosity , @xmath211 , the central regions of the disk remain optically thick throughout the calculations . note that reducing the disk mass by a factor of five ( as was done for runs a1 m , a2 m , a3 m ) does not affect these overall conclusions . the fluid is simply compressed into a smaller volume , and thus the densities and temperatures that are reached are similar than for the high mass runs . for run a3 m the neutrino luminosity is practically constant at @xmath212 erg s@xmath8 for @xmath213 ms . table [ table : evol ] summarizes the typical disk mass , energy density , accretion rate , luminosity , and duration and energetics of neutrino emission for all runs .	this transition produces an inversion of the lepton gradient in the innermost regions of the flow which drives convective motions , and affects the density and disk scale height radial profiles . the electron fraction remains low in the region close to the black hole , and if preserved in an outflow , could give rise to heavy element nucleosynthesis . our specific initial conditions arise from the binary merger context , and so we explore the implications of our results for the production of gamma ray bursts .	we present a detailed , two dimensional numerical study of the microphysical conditions and dynamical evolution of accretion disks around black holes when neutrino emission is the main source of cooling . such structures are likely to form after the gravitational collapse of massive rotating stellar cores , or the coalescence of two compact objects in a binary ( e.g. , the hulse taylor system ) . the physical composition is determined self consistently by considering two regimes : neutrino opaque and neutrino transparent , with a detailed equation of state which takes into account neutronization , nuclear statistical equilibrium of a gas of free nucleons and alpha particles , blackbody radiation and a relativistic fermi gas of arbitrary degeneracy . various neutrino emission processes are considered , with capture onto free nucleons providing the dominant contribution to the cooling rate . we find that important temporal and spatial scales , related to the optically thin / optically thick transition are present in the disk , and manifest themselves clearly in the energy output in neutrinos . this transition produces an inversion of the lepton gradient in the innermost regions of the flow which drives convective motions , and affects the density and disk scale height radial profiles . the electron fraction remains low in the region close to the black hole , and if preserved in an outflow , could give rise to heavy element nucleosynthesis . our specific initial conditions arise from the binary merger context , and so we explore the implications of our results for the production of gamma ray bursts .