bluuebunny/crossref_metadata_2025 huggingface dataset:
NoteThe stringent response genesrelAandspoTare important forEscherichia colibiofilms under slow-growth conditions
Authors: Balzer Grant J , McLean Robert J.C
Published: October 2002

In order to see whether the stringent response was involved in biofilm formation, Escherichia coli DS291 (MG1655), and its isogenic relA spoT derivative were grown for 48 h in a chemostat at dilution rates of 0.025 and 0.25 h1under serine limitation. The absence of the stringent response genes relA and spoT had little effect on the planktonic cell concentrations. However, a significant (P < 0.001) reduction in biofilm cell density of the relA spoT mutants was seen at a doubling time of 40 h. At a doubling time of 4 h, differences in biofilm cell density were not significant. Scanning confocal laser microscopy demonstrated the cell densities of microcolonies in the relA spoT mutant to be lower than those in the wild type. Using a microtiter plate assay, we found biofilm formation in relA spoT mutants to be similarly reduced in minimal media but to be enhanced in rich media (LuriaBertani broth). No significant differences in biofilm formation were observed between wild type and isogenic relA mutants under any growth conditions. Overall, these results suggest that both stringent response genes relA and spoT are important in nutrient-limited biofilms. Key words: biofilm, stringent response, nutrient limitation, microcolony, Escherichia coli.
Overstory litter inputs and nutrient returns in an old-growth temperate forest ecosystem, Olympic National Park, Washington
Authors: Edmonds Robert L , Murray Georgia LD
Published: October 2002

Overstory litterfall rates and nutrient returns were determined in an old-growth temperate rainforest watershed in the Hoh River valley, Olympic National Park, Washington. Litter was sorted into green needles, senescent needles, fine wood, reproductive, and miscellaneous litter (mostly arboreal lichens and mosses). Understory and coarse woody debris inputs were not determined. Total annual overstory litterfall averaged 3594 kg·ha1 and varied among the six plant communities in the watershed. There was a trend for litterfall to be higher in the upper watershed; elevations ranged from 180 to 850 m. Needles provided the greatest amount of litterfall (60%) with woody litter and other material averaging 18 and 22%, respectively. Highest senescent needle litterfall occurred from July to October, but highest woody litterfall was from January to April. Green needles provided only 3% of annual needle litterfall. Green and senescent needle litterfall were related to western hemlock (Tsuga heterophylla (Raf.) Sarg.) basal area, suggesting that this shade-tolerant species was the greatest contributor to needle litterfall. The following quantities (kg·ha1) of nutrients were returned to the forest floor annually: Ca, 26.8; N, 24.6; K, 4.0; Mg, 3.0; P, 2.9; Mn, 1.7; and Na, 1.2.
The marginal cost of structural diversity of mixed uneven-aged hard maple forests
Authors: Kant Shashi
Published: October 2002

Theoretical concepts pertaining to the marginal cost (MC) of the structural diversity of a forest stand are developed. A matrix growth model is estimated for mixed uneven-aged forest stands of hard maple (Acer saccharum Marsh.) from southern Ontario. The estimated growth model is used to derive the MC equations for the Shannon and the Simpson indices of total structural diversity (TSD), species diversity (SD), and tree-size diversity (TD). The effects of exclusion and inclusion of the opportunity cost (OC) on the MC of the TSD are compared. The contributions of SD and TD to the MC of the TSD are disaggregated. The MCs of TSD, SD, and TD for the Shannon and the Simpson indices are iso-elastic. The elasticity of the MC of the TSD for the inclusion of OC is greater than the elasticity of MC of the TSD for the exclusion of OC. The elasticities of MC of TSD, SD, and TD for the Shannon index are greater than the elasticities of MC of TSD, SD, and TD, respectively, for the Simpson index. The elasticities of MC of SD are smaller than the elasticities of MC of TD, for both indices. However, these results are specific to the hard maple forests of southern Ontario and cannot be generalized. Some general features of MC equations of structural diversity are discussed.
A note on the slope correction and the estimation of the length of line features
Authors: Kleinn Christoph , Traub Berthold , Hoffmann Christian
Published: October 2002

Length of line features, such as forest border, is among the ecologically interesting attributes estimated from forest inventories. In hilly terrain, observed line lengths must be corrected for slope. Contrary to the correction for standard area-related attributes (like volume per hectare), an overall correction of plot size is not sufficient, but the actual inclination of each individual line segment must be used for slope correction. This topic is discussed, and a mean correction factor is calculated as a function of terrain inclination assuming a uniform angular distribution of lines on the slope. Furthermore, the question is discussed whether the standard slope correction procedure for fixed-area circular field plots may possibly introduce a systematic error into the estimation of line length and also of standard area-related attributes. It is concluded that no relevant error is to be expected, neither with respect to point estimates nor to interval estimates. Data from the second Swiss National Forest Inventory serves for illustration.
Post-fire forest floor development along toposequences of white spruce - trembling aspen mixedwood communities in west-central Alberta
Authors: Little T I , Pluth D J , Corns I G.W , Gilmore D W
Published: October 2002

After wildfire in the boreal forest, storage of organic carbon (C) begins with the accumulation of forest floor material. Soil properties of Gray Luvisols were studied to determine the differences in development along three toposequences. Our central hypothesis is that slope position does not influence the amount of accumulated organic C and total nitrogen (N) in the forest floor. Organic C and the C/N ratio in the forest floor and in A and B horizons increased from the crest to the toe of the slope. The forest floor contributed 2.0 ± 0.4 kg C·m2 (mean ± SE) at the crest to 3.5 ± 0.5 kg C·m2 at the toe. Throughout the solum, the C/N ratio was lower at the top of the slope compared with the toe (p < 0.05), and there were no differences among slope positions for in situ net N mineralization rates. Leaf area index, used as a proxy for net primary productivity, was greater (p < 0.05) at the toe compared with the crest position, and it was negatively correlated with forest floor total N concentration (r = 0.35, p = 0.027). These results, from mixedwood stands approximately 90 years after the last major fire disturbance, indicate that slope position does influence forest floor organic C by horizon volume (p = 0.02), but not total N concentration (p = 0.07). Despite the apparently lower N availability at the toe position, it exhibited the greatest potential productivity.
Measuring changes in stress and vitality indicators in limed sugar maple on the Allegheny Plateau in north-central Pennsylvania
Authors: Wargo Philip M , Minocha Rakesh , Wong Betty L , Long Robert P , Horsley Stephen B , Hall Thomas J
Published: October 2002

A study established in 1985 in north-central Pennsylvania to determine effects of lime fertilization on declining sugar maple (Acer saccharum Marsh.) was evaluated in 1993 and showed that liming positively affected growth and crown vitality in sugar maple. This effect of lime on sugar maple offered an opportunity to assess other indicators of tree vitality and their response to lime additions. Foliar polyamines, starch and soluble sugars in root tissues, and cambial electrical resistance (CER) at breast height were evaluated. Foliar putrescine, soluble sugars, and CER decreased, while starch increased in lime-treated trees. Changes in these indicators were correlated with tree growth and crown vitality, which improved in limed plots. However, they were more highly correlated with lime-induced changes in foliar and soil elements and soil pH. Putrescine, soluble sugars, and CER decreased and starch increased, as Ca and Mg and molar ratios of Ca/Al and Mg/Mn increased and as Al and Mn decreased in both soil and foliage, and as soil pH increased. Results showed the beneficial effect of lime on tree vitality that was not reflected in visual assessments of crown vitality and demonstrated the potential utility of these physiological and biochemical measures as indicators of vitality in sugar maple.
Effect of nursery conditioning treatments and fall fertilization on survival and early growth of Pinus taeda seedlings in Alabama, U.S.A.
Authors: South David B , Donald D GM
Published: October 2002

Four seedling conditioning treatments and four fall fertilization treatments were applied to loblolly pine (Pinus taeda L.) seedlings in a bare-root nursery in Alabama. Three conditioning treatments involved undercutting plus root wrenching (two, four, and six times), and a fourth treatment included top-pruning (three times) and no undercutting. Fertilizer treatments consisted of (i) control, (ii) 150 kg/ha of N, (iii) 150 kg/ha of N plus 150 kg/ha of P, and (iv) 150 kg/ha of K. On two sites, seedlings were planted in November, and an equal number were placed in cool storage and planted 6 weeks later in mid-December. Results 5 years after outplanting were generally similar for both sites; however, experimental error terms were higher on the sandy site. As a result, conditioning and fertilizer treatments had a statistically significant effect on volume per hectare at the loamy site but not at the sandy site. Volume per hectare was enhanced by undercutting in August followed by two root wrenchings and fall fertilization with N plus P. Storing seedlings reduced height, groundline diameter, and volume per hectare at both sites and reduced survival at the loamy site. Survival of both freshly planted and stored seedlings was greater than 71% at both sites.
Needle longevity of Scots pine in relation to foliar nitrogen content, specific leaf area, and shoot growth in different forest types
Authors: Pensa Margus , Sellin Arne
Published: October 2002

The aim of the study was to examine whether the variation in needle longevity of Scots pine (Pinus sylvestris L.) is of a community-specific nature. Altogether 300 trees were examined in Vaccinium, dry heath, and pine bog forests in Estonia. Mean number of needle age-classes was 4.1 for all forest types, while mean survivorship of needles averaged 70% in Vaccinium forests and 80% in the others (p < 0.01). Mean mass-based nitrogen content (Nm) of the needles was the highest in Vaccinium forests (11.8 mg·g1, p < 0.05) and lower in dry heath (10.4 mg·g1) and pine bog (9.8 mg·g1) forests. Specific leaf area (SLA) did not differ between Vaccinium (6.3 mm2·mg1) and dry heath (6.0 mm2·mg1) forests but was lower in pine bog forests (5.5 mm2·mg1, p < 0.05). Shoot length increment was the smallest in pine bog forests (45.1 mm·year1, p < 0.05) and did not differ between Vaccinium (92.2 mm·year1) and dry heath (95.2 mm·year1) forests. Our findings confirm that the small-scale variation in needle longevity of Scots pine has a community-specific pattern and is in accordance with the trends in Nm and SLA.
Whitebark pine and white pine blister rust in British Columbia, Canada
Authors: Zeglen Stefan
Published: October 2002

A survey of the health of whitebark pine (Pinus albicaulis Engelm.) was conducted throughout its range in British Columbia, Canada. Over 3 years, 24 070 trees were examined for mortality, incidence of white pine blister rust (Cronartium ribicola J.C. Fisch.), or other damage. About 19% of whitebark pine (>1.3 m in height) were dead, and another 31% had active blister rust infections. Tests of relationships between the proportion of healthy, infected, or dead trees and elevation, latitude, and longitude produced mixed results. The ratio of healthy to infected whitebark pine varies considerably across the province, with a trend of increasing incidence from west to east. Losses to mountain pine beetle (Dendroctonus ponderosae Hopkins) proved minor, but bark stripping by mammals was common. Whitebark pine seedlings (<1.3 m in height) revealed lower rates of mortality (11%) and rust infection (4%) than larger trees. However, the pioneer species whitebark pine was found in less than half the regeneration plots and was usually outnumbered by subalpine fir (Abies lasiocarpa (Hook.) Nutt.). The combination of mature tree mortality, lack of suitable substrate for regeneration, and the incursion of climax species indicates a continued decline in whitebark pine populations in British Columbia.
Generation of fuel type maps from Landsat TM images and ancillary data in Mediterranean ecosystems
Authors: Riaño David , Chuvieco Emilio , Salas Javier , Palacios-Orueta Alicia , Bastarrika Aitor
Published: October 2002

This paper presents methods to generate fuel type maps from remote sensing data at a spatial and temporal scale adequate for operational fire management applications. Fuel type maps account for structural characteristics of vegetation related to fire behaviour and fire propagation. A fuel type classification system adapted to the ecological characteristics of the European Mediterranean basin was adopted for this study. The Cabañeros National Park (in central Spain) area was selected for testing and validating the methods. Fuel type maps were derived from two Landsat TM satellite images and digital elevation data. Atmospheric and topographic corrections of the satellite images were performed to reduce spectral variability. A sensitivity analysis was carried out to determine the most appropriate bands for fuel type mapping. The final classification was checked by an intense field survey, the final classification accuracy being estimated at 83%. The main problem was discriminating among those fuel types that differ only in vegetation height or composition of the understory layer. The mean mapping accuracy was 15 m (0.6 pixels), and no areal discrepancy or boundary displacement with vegetation maps was apparent.
The effects of dwarf mistletoe, witches' brooms, stand structure, and site characteristics on the crown architecture of lodgepole pine in Oregon
Authors: Godfree R C , Tinnin R O , Forbes R B
Published: October 2002

We investigated the importance of lodgepole pine dwarf mistletoe (Arceuthobium americanum Nutt.) in determining the height to crown top (HCT), height to crown base (HCB), and live crown ratio (LCR) of 2025 lodgepole pine (Pinus contorta var. murrayana (Grev. & Balf.) Engelm.) growing over a 24-km2 study site in central Oregon. We compared the effects of infection and associated witches' brooms with those of site topography, soil type, shrub cover, stand density, and the abundance of mature ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws). using multiple regression and path analysis. The density of dominant-size P. contorta was consistently the most important factor influencing HCT, HCB, and LCR across the study site. In dense stands, trees tended to have elevated crown bases due to self-pruning and, hence, lower values of LCR. Dwarf mistletoe and related witches' brooms uniquely explained 6.9% of the variance in LCR, which was close to that of dominant P. contorta (7.1%) and more than that of soil type (3.0%), but explained only 2.6% of the variance in HCB, which was less than that of dominant P. contorta (6.5%) and soil type (4.6%). Regression models suggest that heavily infected trees should be 18% shorter and have crown bases 37% lower than uninfected trees, while moderately infected trees should have an LCR over 20% larger than that of uninfected and heavily infected trees. We also found that the largest 25 heavily infected trees sampled were approximately 19% shorter and 1113% smaller in diameter than the largest 25 uninfected trees. The results suggest that dwarf mistletoe can be an important factor in determining the crown dimensions of P. contorta but that these effects may be interpreted only in the context of site characteristics and stand structure.
Challenges facing Chamaecyparis nootkatensis seed orchards: low seed production, pollen-cone abortion, self-pollination, and accelerated embryo development
Authors: Anderson Erika D , Owens John N , Colangeli Anna M , Russell John H
Published: October 2002

Seed orchard production of Chamaecyparis nootkatensis (D. Don) Spach seed faces several challenges including low seed production, pollen-cone abortion, self-pollination, and accelerated reproductive development. In a seed orchard study in 1988 and 1989, approximately eight seeds were produced per cone, but only one to three seeds per cone contained viable embryos. Pollen-cone abortion in 21 clones ranged from 6 to 87% in 19891990 and from 0 to 6% in 19901991. A bud mite, identified as Trisetacus chamaecypari Smith, was consistently associated with pollen-cone abortion in two orchard locations. This mite may be the cause or simply a symptom of unhealthy pollen cones. In a pollination study involving wind, self, and cross pollinations on five clones, self-pollinated cones had significantly fewer seeds containing embryos (4%) compared with the other treatments (2833%). Pollen-cone development at a seed orchard occurred in July and August 1990 and was comparable with natural stand phenology. However, embryo development was significantly accelerated, with embryos at a seed orchard substantially larger than embryos at the natural stand at comparable times.
Spacing rectangularity effect on the growth of loblolly pine plantations
Authors: Sharma Mahadev , Burkhart Harold E , Amateis Ralph L
Published: October 2002

The effect of spacing rectangularity on tree growth and stand development was evaluated using tree data obtained annually from a loblolly pine (Pinus taeda L.) spacing trial monitored through age 16 years. In this trial, plots with an initial planting density of 2240 trees/ha occur at slightly and highly rectangular spacings. Spacings with rectangularities 3:4 and 1:3 were used to evaluate the rectangularity effect. Survival and the development of height, diameter, volume per hectare, and basal area per hectare of loblolly pine trees were not affected by rectangularity. Diameter and height distributions were found to be a function of age but not a function of the rectangularity of initial spacing. Crown width, however, was affected by rectangularity. The crown width was larger at larger row or column distance than at smaller row or column distance, but the ratio of crown widths between and within rows was not equal to the rectangularity of the original planting spacing.
INTELLIGENT HIGH-PERFORMANCE CRAWLERS USED TO REVEAL TOPIC-SPECIFIC STRUCTURE OF THE WWW
Authors: LŐRINCZ ANDRÁS , KÓKAI ISTVÁN , MERETEI ATTILA
Published: October 2002

The slogan that "information is power" has undergone a slight change. Today, "information updating" is in the focus of interest. The largest source of information today is the World Wide Web. Fast search methods are needed to utilize this enormous source of information. In this paper our novel crawler using support vector classification and on-line reinforcement learning is described. We launched crawler searches from different sites, including sites that offer, at best, very limited information about the search subject. This case may correspond to typical searches of non-experts. Results indicate that the considerable performance improvement of our crawler over other known crawlers is due to its on-line adaptation property. We used our crawler to characterize basic topic-specific properties of WWW environments. It was found that topic-specific regions have a broad distribution of valuable documents. Expert sites are excellent starting points, whereas mailing lists can form trape for the crawler. These properties of the WWW and the emergence of intelligent "high-performance" crawlers that monitor and search for novel information together predict a significant increase of communication load on the WWW in the near future.
CLUSTERING WEB VISITORS BY BAST, ROBUST AND CONVERGENT ALGORITHMS
Authors: ESTIVILL-CASTRO VLADIMIR , YANG JIANHUA
Published: October 2002

The identification of categories of visitors to a Web-site is very useful towards improved Web designs and improved Web applications. However, the large volume involved in mining access-logs and visitation paths, and the uncertainty to fully identify the visitor demand efficient clustering algorithms that are also resistant to noise and outliers. Also, visitation paths are discrete, and dissimilarity between visitation paths involves sophisticated evaluation and results in attribute-vectors with large dimension. We provide randomized, iterative clustering algorithms for generic dissimilarity in paths. Our algorithms are robust because they use medians rather than means as estimators of location, and the resulting representative of a cluster is actually a path in the data set. We demonstrate mathematically that our algorithms converge and have subquadratic complexity. We also show experimentally that they are resistant to noise by recovering clusters from synthetic data generated by a mixture of distributions of paths in a graph. Our non-crisp method proposed generalizes approaches that allow a data item to have a degree of membership in a cluster.
AN INTELLIGENT AGENT FOR WEB ADVERTISEMENTS
Authors: NG VINCENT , HO MOK KWAN
Published: October 2002

The rapid growth of Internet users attracts advertisers to post their advertisements in Internet. The probabilistic selection algorithm was not satisfactory; while other advertising agents are unable to guarantee the quality due to insufficient and unstable user information. This paper describes a new advertising agent based on user information. The users' interests are discovered by the Order Pattern Mining algorithm first, then the Gaussian curve transformation is applied to represent their profiles. For the advertisements, we use the keywords from different categories to construct the advertisement profiles as Gaussian curves also. This allows us to select advertisements based on the intersections of the different profiles according to users' preferences in an effective and efficient mechanism. A prototype of the Intelligent Advertising Agent has been developed with Java and Oracle. From our evaluations, we observed that about 70% of the test cases are successful in making predictions which generated the most favorable category that the users are interested.
MONA IMPLEMENTATION SECRETS
Authors: KLARLUND NILS , MØLLER ANDERS , SCHWARTZBACH MICHAEL I.
Published: October 2002

The MONA tool provides an implementation of automaton-based decision procedures for the logics WS1S and WS2S. It has been used for numerous applications, and it is remarkably efficient in practice, even though it faces a theoretically non-elementary worst-case complexity. The implementation has matured over a period of six years. Compared to the first naive version, the present tool is faster by several orders of magnitude. This speedup is obtained from many different contributions working on all levels of the compilation and execution of formulas. We present an overview of MONA and a selection of implementation "secrets" that have been discovered and tested over the years, including formula reductions, DAGification, guided tree automata, three-valued logic, eager minimization, BDD-based automata representations, and cache-conscious data structures. We describe these techniques and quantify their respective effects by experimenting with separate versions of the MONA tool that in turn omit each of them.
A STRONG OPERATOR TOPOLOGY ADIABATIC THEOREM
Authors: ELGART ALEXANDER , SCHENKER JEFFREY H.
Published: October 2002

We prove an adiabatic theorem for the evolution of spectral data under a weak additive perturbation in the context of a system without an intrinsic time scale. For continuous functions of the unperturbed Hamiltonian the convergence is in norm while for a larger class functions, including the spectral projections associated to embedded eigenvalues, the convergence is in the strong operator topology.
A MICROSTATES APPROACH TO RELATIVE FREE ENTROPY
Authors: SHLYAKHTENKO DIMITRI
Published: October 2002

We introduce a microstates-based notion of relative free entropy. This quantity is a microstates analog of Voiculescu's microstates-free relative entropy χ*(X1,…,Xn:B), and coinsides with his microstates entropy in the case that the algebra B consists of just mulitplies of identity.

More generally, there is a formula relating the two in the case that B is a matrix algebra. We discuss several properties of our relative entropy, including maximization results and an infinitesimal change of variables formula.
REGULAR OBJECTS, MULTIPLICATIVE UNITARIES AND CONJUGATION
Authors: PINZARI C. , ROBERTS J. E.
Published: October 2002

The notion of left (respectively right) regular object of a tensor C*-category equipped with a faithful tensor functor into the category of Hilbert spaces is introduced. If such a category has a left (respectively right) regular object, it can be interpreted as a category of corepresentations (respectively representations) of some multiplicative unitary. A regular object is an object of the category which is at the same time left and right regular in a coherent way. A category with a regular object is endowed with an associated standard braided symmetry.

Conjugation is discussed in the context of multiplicative unitaries and their associated Hopf C*-algebras. It is shown that the conjugate of a left regular object is a right regular object in the same category. Furthermore the representation category of a locally compact quantum group has a conjugation. The associated multiplicative unitary is a regular object in that category.
FLUCTUATIONS OF CLUSTER NUMBERS IN PERCOLATION
Authors: TIGGEMANN DANIEL
Published: October 2002

In order to study fluctuations in percolating systems, lattices for sizes up to L = 100 000 have been simulated several thousand times using the Hoshen–Kopelman algorithm. Distributions of cluster numbers are Gaussians for small clusters and half-sided quasi-Gaussians for large clusters. The variance of cluster numbers is proportional to the mean, with power-law deviations for small clusters. Higher moments like skewness and kurtosis were also studied.
EFFECTS OF RAMPS IN THE NAGEL–SCHRECKENBERG TRAFFIC MODEL
Authors: HUANG DING-WEI
Published: October 2002

We study the effects of on-ramp and off-ramp to the traffic flow in a cellular automaton. The stochastic noise and the extended hopping are included. The phase diagram is obtained. Three distinct phases are observed. The density profiles are analyzed. In the maximum current phase, standing traffic jams emerge in the upstream of the on-ramp. A region of free flow is observed in the downstream of the off-ramp. In between the ramps, a scaled density profile is observed in one branch and a phase separation is observed in the other branch.
COMPUTER SIMULATION OF PHOTON ANTICORRELATION EXPERIMENT USING ADDITIVE PRE-DETECTION NOISE AND FINITE INSTRUMENT BANDWIDTH
Authors: SULCS S. , OSBORNE C. F.
Published: October 2002

The photon anticorrelation experiment is simulated with the unquantized Maxwell field by implementing realistic instrument bandwidth and signal to noise ratio. The results strongly violate an inequality believed to be satisfied by all semiclassical theories, which opens up a classical interpretation that rivals quantum optics and casts doubt on potential quantum computer applications that involve optical fields.
ON ARITHMETIC DETECTION OF GREY PULSES WITH APPLICATION TO HAWKING RADIATION
Authors: ROSU HARET C. , PLANAT MICHEL
Published: October 2002

Micron-sized black holes do not necessarily have a constant horizon temperature distribution. The black hole remote-sensing problem means to find out the "surface" temperature distribution of a small black hole from the spectral measurement of its (Hawking) grey pulse. This problem has been previously considered by Rosu, who used Chen's modified Möbius inverse transform. Here, we hint on a Ramanujan generalization of Chen's modified Möbius inverse transform that may be considered as a special wavelet processing of the remote-sensed grey signal coming from a black hole or any other distant grey source.
COSMIC SCALAR FIELDS WITH FLAT POTENTIAL
Authors: van HOLTEN J. W.
Published: October 2002

The dynamics of cosmic scalar fields with flat potential is studied. Their contribution to the expansion rate of the universe is analyzed, and their behavior in a simple model of phase transition is discussed.
A METHOD OF GENERATING EXACT SOLUTIONS OF THE TIME-DEPENDENT SCHRÖDINGER EQUATION WITH TIME-DEPENDENT MASS
Authors: SCHULZE-HALBERG AXEL
Published: October 2002

Extending the method presented in our previous paper,12 we map the time-dependent Schrödinger equation (TDSE) with time-dependent mass on a stationary Schrödinger equation for a nonconstant potential. On solving the latter, we can thus generate a large class of exact solutions of the original TDSE. Several examples are given, including potentials of power-law and modified Pöschl–Teller type.
A THEORY OF JET DEFINITION
Authors: TKACHOV FYODOR V.
Published: October 2002

A systematic framework for jet definition is developed from first principles of physical measurement, quantum field theory, and QCD. A jet definition is found which:

• is theoretically optimal in regard of both minimization of detector errors and inversion of hadronization;

• is similar to a cone algorithm with dynamically negotiated jet shapes and positions found via shape observables that generalize the thrust to any number of axes;

• involves no ad hoc conventions;

• allows a fast computer implementation.7

The framework offers an array of options for systematic construction of quasi-optimal observables for specific applications.
SCREENING LENGTH, DISPERSION RELATIONS AND QUARK POTENTIAL IN THERMO FIELD DYNAMICS
Authors: ZHAO WANYUN , KHANNA F. C.
Published: October 2002

The screening length in a quark–gluon plasma, the dispersion relations of thermal gluon self-energy and the quark potential at high temperature are studied within the thermo field dynamics framework. By calculating the real and imaginary parts, of the gluon self-energy in one-loop order in thermo field dynamics, we obtain an expression for the screening length in a quark–gluon plasma and the dispersion relation between the real and imaginary parts. At high temperature, using photon exchange between electron-positron in a skeleton expansion and ladder approximation, the screened Coulomb potential and an expression for the screened quark potential is obtained.
DEPARAMETRIZATION AND QUANTIZATION OF THE TAUB UNIVERSE
Authors: GIRIBET GASTÓN , SIMEONE CLAUDIO
Published: October 2002

Previous analysis about the deparametrization and path integral quantization of cosmological models are extended to models which do not admit an intrinsic time. The formal expression for the transition amplitude is written down for the Taub anisotropic universe with a clear notion of time. The relation existing between the deparametrization associated to gauge fixation required in the path integral approach and the procedure of reduction of the Wheeler–DeWitt equation is also studied.
GRAVITY AND COSMOLOGY ON A BRANE-WORLD
Authors: BATTYE RICHARD A.
Published: October 2002

Contrary to everyday experience it is possible to construct models with more than three spatial dimensions which are compatible with linearized 4D Einstein gravity and homogeneous isotropic cosmologies. The simplest of these models have co-dimension one and are subjected to reflection symmetry. We discuss various extensions, in particular the inclusion of a scalar field and the relaxation of the assumption of reflection symmetry.
CHAOS IN STRING COSMOLOGY
Authors: DAMOUR THIBAULT
Published: October 2002

We briefly review recent work which established the existence of chaos in the generic cosmological solutions of the tree-level low-energy effective actions coming out of string theory, and linked this chaos to the Weyl groups of some hyperbolic Kac-Moody algebras.
NEW PROPERTIES OF MATTER IN (A)dS AND THEIR CONSEQUENCES
Authors: DESER S.
Published: October 2002

I review briefly, primarily for relativists, a series of recent results, obtained with A. Waldron, on the novel behavior of massive higher (s > 1) spin systems in constant curvature backgrounds. We find that the cosmological constant Λ, together with the mass parameter, define a "phase plane" in which partially massless gauge invariant lines separate allowed regions from forbidden, non-unitary, ones. These lines represent short multiplet systems, with missing lower helicities, removed by novel local gauge invariances, and (despite having m ≠ 0) propagating on the light cone. In the limit of an infinite tower of these higher spin bosons and fermions, unitarity requires Λ to vanish.
SPACE–TIME VARIATION OF PHYSICAL CONSTANTS AND THE EQUIVALENCE PRINCIPLE
Authors: NORDTVEDT KENNETH
Published: October 2002

Location-dependence of physical parameters such as the electromagnetic fine structure constant and Newton's G produce body accelerations which violate universality of free fall rates testable with laboratory and space experiments. Theoretically related cosmological time variation of these same parameters are also constrained by experiments such as lunar laser ranging, and these time variations produce accelerations of bodies relative to a preferred cosmological inertial frame.
IMPULSIVE LIGHT-LIKE SIGNALS
Authors: BARRABÈS C. , HOGAN P. A.
Published: October 2002

A general characterisation of an impulsive light–like signal was given1,2. The signal may consist of a shell of null matter and/or an impulsive gravitational wave. Both parts of the signal can be unambiguously identified3,4. The signals can be used to model bursts of gravitational radiation and light– like matter accompanying cataclysmic events such as supernovae and neutron star collisions. Also in high speed collisions of compact objects such as black–holes or neutron stars the gravitational fields of these objects resemble those of impulsive light–like signals when the objects are boosted to the speed of light. Several examples of impulsive light–like signals were presented, in particular those produced by recoil effects5 and by the Aichelburg–Sexl boost of an isolated gravitating multipole source6. The detection of these signals was also discussed7.
CHOPTUIK SCALING AND QUASINORMAL MODES IN THE ADS/CFT CORRESPONDENCE
Authors: BIRMINGHAM DANNY
Published: October 2002

The exact quasinormal frequencies for scalar perturbations of the three-dimensional BTZ black hole were presented1. The timescale for the decay of the scalar perturbation is given by the imaginary part of the quasinormal frequencies. Via the AdS/CFT correspondence, one then obtains a prediction of the timescale for return to equilibrium of the dual conformal field theory. By studying a two-particle collision process, an exact analytic expression for the Choptuik scaling parameter of the BTZ black hole was obtained2. A possible connection between the Choptuik scaling parameter and the imaginary part of the quasinormal frequencies was explored1.
GAMMA-RAY BURSTS FROM GRAVITATIONAL COLLAPSE
Authors: CASADIO R.
Published: October 2002

A possible origin of gamma-ray bursts is the gravitational collapse of compact objects. A semiclassical analysis, which employs the Born-Oppenheimer approximation in order to treat gravity as classical while matter is quantized1, was first applied to homogeneous spheres of dust2,3 and (thick) non-radiating shells 4. We later derived an effective Lagrangian for (thin) radiating shells5 which allowed us to study the evolution of a self-gravitating shell of bosonic matter coupled to a scalar radiation field. We showed that the matter can form a condensate and the matter degrees of freedom are excited, because of the non-adiabaticity of the collapse, at the expense of gravitational energy4,6. Upon decaying back to the ground state, the excited matter energy is subsequently transferred to the radiation field. In fact, the system can convert large fractions of its gravitational energy into radiation and the time evolution of the radius of the shell is then significantly slowed down with respect to the non-radiating case. This provides a new mechanism to extract energy from collapsing matter which might play a role as a source of gamma-ray bursts.
HIGHER-ORDER GEODESIC DEVIATIONS AND THE CALCULUS OF RELATIVISTIC ORBITS
Authors: COLISTETE R.
Published: October 2002

Starting with an exact and simple geodesic, we generate approximate geodesics1,2 by summing up higher-order geodesic deviations in a fully relativistic scheme. We apply this method to the problem of orbit motion of test particles in Schwarzschild3 and Kerr metrics; from a simple circular orbit as the initial geodesic we obtain finite eccentricity orbits as a Taylor series with respect to the eccentricity. The explicit expressions of these higher-order geodesic deviations are derived using successive systems of linear equations with constant coefficients, whose solutions are of harmonic oscillator type. This scheme is best adapted for small eccentricities, but arbitrary values of M/R. We also analyse the possible application to the calculation of the emission of gravitational radiation from non-circular orbits around a very massive body3.
FINDING CONFORMAL KILLING VECTORS FROM THE INVARIANT CLASSIFICATION SCHEME
Authors: EDGAR BRIAN , LUDWIG GARRY
Published: October 2002

The invariant classification (Karlhede classification)1 of a particular spacetime fixes (up to isotropy) an intrinsic tetrad for the spacetime, in terms of the Riemann tensor and its derivatives. Exploiting this tetrad, it has been shown how to determine the number of Killing vectors which exist 2, and also whether a proper homothetic Killing vector exists 3. The first part of the talk outlined a procedure for finding explicitly homothetic and Killing vectors by exploiting the symmetry properties of the intrinsic tetrad 4,5.

In general, it is not always possible to use this same tetrad to investigate proper conformal Killing vectors by the same methods. In this talk it was suggested to modify the invariant classification procedure so that only conformally invariant conditions are used for fixing the tetrad in terms of the Riemann tensor and its derivatives. This would mean that the existence of proper conformal Killing vectors could be deduced directly from the modified invariant classification scheme, and then found explicitly 6.
SCALAR PERTURBATIONS IN A PRIMORDIAL INFLATIONARY SCENARIO
Authors: FABRIS J. , SPINDEL Ph.
Published: October 2002

We compute the spectral index for scalar perturbations generated in a primordial inflationary model2. In this model, the transition of the inflationary phase to the radiative era is achieved through the decay of the cosmological term leading a second order phase transition and the characteristics of the model allow to implement a set of initial conditions where the perturbations display a thermal spectrum when they emerge from the horizon.

[Formula: see text]

The obtained value for the spectral index is equal to 2, a result that depends very weakly on the various parameters of the model and on the initial conditions used. This "negative" result pleads for the standard inflationary scenario, but of course cannot prove it and the problem of the interpretation of the inflaton remains open2.
EINSTEIN'S EQUIVALENCE PRINCIPLE AND THE GRAVITATIONAL RED SHIFT
Authors: FLORIDES PETROS S.
Published: October 2002

Long before the general theory of relativity was finally formulated in 1916, it was claimed that the following argument, based on (the strong) Einstein's equivalence principle (EP for short), predicted the well known and experimentally observed phenomenon of the gravitational red shift; precisely the same argument is being used to this day in almost all books on general relativity to derive the same phenomenon (see, for example, Refs. 1, 2):

Consider "Einstein's elevator" at rest on the Earth's surface with an emitter (E) fixed on the floor of the elevator, and a receiver (R) fixed on the ceiling directly above E and distance h from it. Let E send light signals, at frequency νE, to R and let the frequency at which they are received by R be νR. To find the relationship between νE and νR we invoke the EP and consider, instead, E and R as fixed in an elevator which is accelerating relative to an inertial frame S in gravitation-free space with constant acceleration g in the direction [Formula: see text], g being the acceleration due to gravity on the Earth's surface. At time t = 0, when E is assumed to be at rest in S, E emits a light wave towards R. The time it takes the wave to reach R is roughly t = h/c, where c is the speed of light in S. But in this time R has acquired the velocity [Formula: see text] and, therefore, there is a consequent Doppler shift given by [Formula: see text]. By the EP the same result must hold when E and R are fixed near the Earth's surface. In this case gh = △Φ = Φ(R) - Φ(E), so that in the Earth's gravitational field we have [Formula: see text], which is the standard formula for the gravitational red shift.

Simple and straight forward as the above argument may seem, we shall show in this lecture that it is, in fact, fundamentally flawed in two important respects. We shall present a new argument, entirely within the framework of classical mechanics (just as the above argument), which is free from these two flaws. Alas!, it leads to zero gravitational red shift for the case dealt with in the above argument. It is argued that this result not only does it not invalidate the general theory of relativity but it strengthens it; for, the full theory of general relativity alone, irrespective of its historical development, can correctly and unambiguously predict the observed gravitational red shift.
NEW LOWER BOUNDS FOR WARP DRIVE ENERGY
Authors: GAUTHIER C. , GRAVEL P. , MELANSON J.
Published: October 2002

The introduction of the warp drive metric by Alcubierre1 has aroused great interest over the past few years. Using an uncertainty-type principle, Ford and Pfenning2 proved that the warp drive transport of a spaceship in a regular bubble having a radius of 100 m is unrealistic. However, Van Den Broeck3 has shown that the situation largely improves when one uses a warp drive bubble with a small surface area and large spatial volume.

Putting aside many physics problems related to the realization of the warp drive concept, we show in this paper4 how to modify Van Den Broeck's idea to improve his results. We find new lower bounds for the warp drive energy by working on parameters whose latitude has never been considered before. We also consider micro warp drive bubbles which can be treated as physical entities of their own and could possibly be used to transmit information faster than the speed of light. The conditions prevailing just after the Big Bang allow the spontaneous formation of such micro bubbles which could still be present in our period of time.
STRING'S CURRENT INDUCED BY THE DILATONIC COUPLING OF GRAVITY
Authors: GUIMARÃES MARIA E. X.
Published: October 2002

The nature of an ordinary cosmic string1 in the framework of a scalar-tensor extension of gravity is investigated. It is shown that in this case, the dilaton field can act as a timelike or a spacelike current traveling along the string, and localized into it2. Apart from the fact that the current can not be formed after the string forming phase transition but exactly at the same time, since the dilaton is not an ordinary scalar field but a component of the gravitational interaction configuration would resemble very much the usual superconducting strings first proposed by Witten3. This means that a network of strings here produced would suffer from the vorton excess problem4, leading to an actual cosmological catastrophe from which one can derive strong constraints on the relevant theories.
CONSERVED CURRENT FOR GENERAL TELEPARALLEL MODELS
Authors: ITIN Y.
Published: October 2002

The obstruction for the existence of an energy-momentum tensor for the gravitational field in GR is connected with vanishing of first order invariants in (pseudo) Riemannian geometry. This specific geometric property is not valid in alternative geometrical structures1,2.

A parallelizable differentiable 4D-manifold endowed with a class of smooth coframe fields ϑa is considered. A general 3-parameter class of global Lorentz invariant teleparallel models is considered. It includes a 1-parameter subclass of models with the Schwarzschild coframe solution (generalized teleparallel equivalent of gravity) 3. By introducing the notion of a 3-parameter conjugate field strength F linear in the strength Ca = dϑa the coframe Lagrangian is rewritten in the Maxwell-Yang-Mills form L = 1/2Fa ∧ Ca. The field equation turns out to have a form d * Fa = Ta completely similar to the Maxwell field equation.

By applying the Noether procedure, the source 3-form Ta is shown to be connected with the diffeomorphism invariance of the Lagrangian. Thus the source Ta of the coframe field is interpreted as the total conserved energy-momentum current of the coframe field and matter4. The energy-momentum tensor is defined as a map of the module of current 3-forms into the module of vector fields 5. Thus an energy-momentum tensor for the coframe is defined in a diffeomorphism invariant and a translational covariant way. The total energy-momentum current of a system is conserved. Thus a redistribution of the energy-momentum current between material and coframe (gravity) field is possible in principle, unlike as in the standard GR.

The result is: The standard GR has a neighborhood of viable models with the same Schwarzschild solutions. These models however have a better Lagrangian behavior and produce an invariant energy-momentum tensor.
PRIMARY SCALAR HAIR OF BLACK HOLES IN EFFECTIVE STRING THEORY
Authors: MIGNEMI S.
Published: October 2002

Black holes in string theories can be studied by means of effective gravity-matter actions. These contain, among others, non-minimally coupled scalar fields, as the dilaton and moduli arising from the compactification of the extra dimensions1. The presence of non-minimal couplings prevents the application of the well known no-hair theorems2, so that it is possible to find regular black hole solutions with scalar hair. Solutions with non-trivial dilaton hair are known for Maxwell3 and Gauss-Bonnet4 black holes. In these cases the dilaton charge is a function of the other parameters of the solutions (secondary hair). However, it has recently been shown that when moduli fields are taken into account as well, one can obtain solutions where the scalar charges of the moduli are independent parameters (primary scalar hair)5,6. The thermodynamics of these black holes has been investigated. In particular, in the Maxwell case a condition for extremality has been obtained, which sets a lower bound for the mass in terms of the magnetic and scalar charges7. Similarly in the Gauss-Bonnet case, a minimal allowed value for the mass has been found, which depends only on the scalar charges and can be interpreted as a ground state for the Hawking evaporation process of the black hole6.
CONFORMAL CONNECTION AND EQUIVALENCE PROBLEM FOR THIRD ORDER ODEs
Authors: NUROWSKI PAWEL
Published: October 2002

The equivalence problem for the third order ODEs solved by E. Cartan1 and S. S. Chern2 is reconsidered. We consider third order ODEs of the form y′′′ = F(x,y,y′,y′′) for which the Wunshman invariant I vanishes. All such ODEs split into equivalence classes with respect to the contact transformations of the variables. As shown by E. T. Newman3 and collaborators such equations are also in one-to-one correspondence with conformal classes of Lorentian three-metrics. We supplement Cartan-Chern-Newman results by providing explicit expressions for all the contact invariants of an ODE with I = 0. The invariants are explicitly written in terms of the function F and its partial derivatives. Explicit expression for the associated Cartan's O(2,3) connection is also given. The curvature of this conformal connection is reinterpreted in terms of the Cotton-York tensor of the Lorentzian three-metric associated with the equation.