bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reference frames, gauge transformations and gravitomagnetism in the post-Newtonian theory of the lunar motion
Authors: Xie Yi , Kopeikin Sergei 
Published: January 2010

AbstractWe construct a set of reference frames for description of the orbital and rotational motion of the Moon. We use a scalar-tensor theory of gravity depending on two parameters of the parametrized post-Newtonian (PPN) formalism and utilize the concepts of the relativistic resolutions on reference frames adopted by the International Astronomical Union in 2000. We assume that the solar system is isolated and space-time is asymptotically flat. The primary reference frame has the origin at the solar-system barycenter (SSB) and spatial axes are going to infinity. The SSB frame is not rotating with respect to distant quasars. The secondary reference frame has the origin at the Earth-Moon barycenter (EMB). The EMB frame is local with its spatial axes spreading out to the orbits of Venus and Mars and not rotating dynamically in the sense that both the Coriolis and centripetal forces acting on a free-falling test particle, moving with respect to the EMB frame, are excluded. Two other local frames, the geocentric (GRF) and the selenocentric (SRF) frames, have the origin at the center of mass of the Earth and Moon respectively. They are both introduced in order to connect the coordinate description of the lunar motion, observer on the Earth, and a retro-reflector on the Moon to the observable quantities which are the proper time and the laser-ranging distance. We solve the gravity field equations and find the metric tensor and the scalar field in all frames. We also derive the post-Newtonian coordinate transformations between the frames and analyze the residual gauge freedom of the solutions of the field equations. We discuss the gravitomagnetic effects in the barycentric equations of the motion of the Moon and argue that they are beyond the current accuracy of lunar laser ranging (LLR) observations.
Overview of current precision clocks and future prospects
Authors: Beard R. L. 
Published: January 2010

AbstractToday's time and frequency standards range from the most sophisticated reference standards to the smallest oscillator for handheld radios. The technical requirements and technologies needed are different for the various applications but they derive from similar physical concepts. These different technologies can be categorized into four major areas, reference standards, mobile systems, man-portable (handheld) and space systems. These areas are the core areas of time and frequency standard applications and different areas of technology are needed to address them. This presentation discusses the time and frequency standards used or available for these areas.
Time ephemeris and general relativistic scale factor
Authors: Fukushima Toshio 
Published: January 2010

AbstractTime ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG (Fukushima 1995). It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitably needed in conducting precise four dimensional coordinate transformations among various spacetime coordinate systems such as the GCRS and BCRS (Soffelet al. 2003). Also, by means of the time average operation, they are used in determining the information on scale conversion between the pair of coordinate systems, especially the difference of the general relativistic scale factor from unity such asLC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995). It gave an estimate ofLCas 1.4808268457(10) × 10−8, which was incorrect by around 2 × 10−16. This was caused by taking the wrong sign of the post-Newtonian contribution in the final summation. Four years later, we updated TE245 to TE405 associated with DE405 (Irwin and Fukushima 1999). This time the renewed vale ofLCis 1.48082686741(200) × 10−8Another four years later, by using a precise technique of time average, we improved the estimate of Newtonian part ofLCfor TE405 as 1.4808268559(6) × 10−8(Harada and Fukushima 2003). This leads to the value ofLCasLC= 1.48082686732(110) × 10−8. If we combine this with the constant defining the mean rate of TCG-TT,LG= 6.969290134 × 10−10(IAU 2001), we estimate the numerical value of another general relativistic scale factorLB= 1.55051976763(110) × 10−8, which has the meaning of the mean rate of TCB-TT. The main reasons of the uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. The former is a natural limitation caused by the finite length of numerical planetary ephemerides and the latter is due to the uncertainty of masses of some heavy asteroids. As a compact realization of the time ephemeris, we prepared HF2002, a Fortran routine to compute approximate harmonic series of TE405 with the RMS error of 0.446 ns for the period 1600 to 2200 (Harada and Fukushima 2003). It is included in the IERS Convention 2003 (McCarthy and Petit 2003) and available from the IERS web site;http://tai.bipm.org/iers/conv2003/conv2003_c10.html.
Relativistic equations of motion of massive bodies
Authors: Blanchet Luc 
Published: January 2010

AbstractHighly relativistic equations of motions will play a crucial role for the detection and analysis of gravitational waves emitted by inspiralling compact binaries in detectors LIGO/VIRGO on ground and LISA in space. Indeed these very relativistic systems (with orbital velocities of the order of half the speed of light in the last orbital rotations) require the application of a high-order post-Newtonian formalism in general relativity for accurate description of their motion and gravitational radiation [1]. In this contribution the current state of the art which has reached the third post-Newtonian approximation for the equations of motion [2–6] and gravitational waveform [7–9] has been described (see [10] for an exhaustive review). We have also emphasized the successful matching of the post-Newtonian templates to numerically generated predictions for the merger and ring-down in the case of black-hole binaries [11].
Proper stellar directions and astronomical aberration
Authors: Crosta Mariateresa , Vecchiato Alberto 
Published: January 2010

AbstractThe general relativistic definition of astrometric measurement needs an appropriate use of the concept of reference frame, which should then be linked to the conventions of the IAU Resolutions (Soffel et al., 2003), which fix the celestial coordinate system. A consistent definition of the astrometric observables in the context of General Relativity is also essential to find uniquely the stellar coordinates and proper motion, this being the main physical task of the inverse ray tracing problem. Aim of this work is to set the level of reciprocal consistency of two relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to guarantee a physically correct definition of light direction to a star, an essential item for deducing the star coordinates and proper motion within the same level of measurement accuracy.
Spectroscopic binary mass determination using relativity
Authors: Zucker Shay , Alexander Tal 
Published: January 2010

AbstractHigh-precision radial-velocity techniques, which enabled the detection of extra-solar planets, are now sensitive to the lowest-order relativistic effects in the data of spectroscopic binary stars (SBs). We show how these effects can be used to derive the absolute masses of the components of eclipsing single-lined SBs and double-lined SBs from Doppler measurements alone. High-precision stellar spectroscopy can thus substantially increase the number of measured stellar masses, thereby improving the mass-radius and mass-luminosity calibrations.
Binary pulsars and tests of general relativity
Authors: Stairs I. H. 
Published: January 2010

AbstractBinary pulsars are a valuable laboratory for gravitational experiments. Double-neutron-star systems such as the double pulsar provide the most stringent tests of strong-field gravity available to date, while pulsars with white-dwarf companions constrain departures from general relativity based on the difference in gravitational binding energies in the two stars. Future observations may open up entirely new tests of the predictions of general relativity.
Astrometric and timing effects of gravitational waves
Authors: Schutz Bernard F. 
Published: January 2010

AbstractGravitational wave detection can be done by precision timing of millisecond pulsars, and (with less likelihood) by precision astrometry on distant objects whose light or radio waves pass through gravitational waves on their way to our observatories. Underlying both of these is the relatively simple theory of light propagation in spacetimes with gravitational waves, which is also the basis of interferometric gravitational wave detectors. I review this theory and apply it to the timing and astrometric methods of detection. While pulsar timing might even be the first way that we directly detect gravitational waves, light deflection by gravitational waves seems out of reach.
Gravitational wave astronomy, relativity tests, and massive black holes
Authors: Bender Peter L. 
Published: January 2010

AbstractThe gravitational wave detectors that are operating now are looking for several kinds of gravitational wave signals at frequencies of tens of Hertz to kilohertz. One of these is mergers of roughly 10M⊙BH binaries. Sometime between now and about 8 years from now, it is likely that signals of this kind will be observed. The result will be strong tests of the dynamical predictions of general relativity in the high field regime. However, observations at frequencies below 1 Hz will have to wait until the launch of the Laser Interferometer Space Antenna (LISA), hopefully only a few years later. LISA will have 3 main objectives, all involving massive BHs. The first is observations of mergers of pairs of intermediate mass (100 to 105M⊙) and higher mass BHs at redshifts out to roughly z=10. This will provide new information on the initial formation and growth of BHs such as those found in most galaxies, and the relation between BH growth and the evolution of galactic structure. The second objective is observations of roughly 10M⊙BHs, neutron stars, and white dwarfs spiraling into much more massive BHs in galactic nuclei. Such events will provide detailed information on the populations of such compact objects in the regions around galactic centers. And the third objective is the use of the first two types of observations for testing general relativity even more strongly than ground based detectors will. As an example, an extreme mass ratio event such as a 10M⊙BH spiraling into a galactic center BH can give roughly 105observable cycles during about the last year before merger, with a mean relative velocity of 1/3 to 1/2 the speed of light, and the frequencies of periapsis precession and Lense-Thirring precession will be high. The LISA Pathfinder mission to prepare for LISA is scheduled for launch in 2011.
The galactic center: The ideal laboratory for studying supermassive black holes
Authors: Eisenhauer Frank 
Published: January 2010

AbstractThe Galactic Center constitutes the best astrophysical evidence for the existence of black holes, and it is the ideal laboratory for studying physics in the vicinity of such objects. The combination of infrared observations of three dimensional orbits of stars within the central light days and the extreme compactness and motionlessness of the radio-counterpart of the gravitational center have shown beyond any reasonable doubt that the Galactic Center harbors a supermassive black hole. The flaring activity from the black hole gives first insights to the physical processes close to the last stable orbit. Here I review the current state of observations and theory of the Galactic Center black hole and give an update on the latest results. I also outline the next steps towards even higher angular resolution observations, which give promise to directly probe the physics and space-time curvature just outside the event horizon.
Optical interferometry from the Earth
Authors: Quirrenbach Andreas 
Published: January 2010

AbstractGround-based optical interferometers can perform astrometric measurements with a precision approaching 10μas between pairs of stars separated by ~10″ on the sky. These narrow-angle measurements can be used to search for extrasolar planets and to determine their orbital parameters, to characterize microlensing events, and to measure the orbits of stars around the black hole at the center of our Galaxy.
Gaia: Astrometric performance and current status of the project
Authors: Lindegren Lennart 
Published: January 2010

AbstractThe scientific objectives of the Gaia mission cover areas of galactic structure and evolution, stellar astrophysics, exoplanets, solar system physics, and fundamental physics. Astrometrically, its main contribution will be the determination of millions of absolute stellar parallaxes and the establishment of a very accurate, dense and faint non-rotating optical reference frame. With a planned launch in spring 2012, the project is in its advanced implementation phase. In parallel, preparations for the scientific data processing are well under way within the Gaia Data Processing and Analysis Consortium. Final mission results are expected around 2021, but early releases of preliminary data are expected. This review summarizes the main science goals and overall organisation of the project, the measurement principle and core astrometric solution, and provide an updated overview of the expected astrometric performance.
Optimising the Gaia scanning law for relativity experiments
Authors: de Bruijne Jos , Siddiqui Hassan , Lammers Uwe , Hoar John , O'Mullane William , Prusti Timo 
Published: January 2010

AbstractGaia is ESA's upcoming astrometry mission, building on the heritage of its predecessor, Hipparcos. The Gaia nominal scanning law (NSL) prescribes the ideal attitude of the spacecraft over the operational phase of the mission. As such, it precisely determines when certain areas of the sky are observed. From theoretical considerations on sky-sampling uniformity, it is easy to show that the optimum scanning law for a space astrometry experiment like Gaia is a revolving scan with uniform rotation around the instrument symmetry axis. Since thermal stability requirements for Gaia's payload require the solar aspect angle to be fixed, the optimum parallax resolving power is obtained by letting the spin axis precess around the solar direction. The precession speed has been selected as compromise, limiting the across-scan smearing of images when they transit the focal plane, providing sufficient overlap between successive “great-circle” scans of the fields of view, and guaranteeing overlap of successive precession loops. With this scanning law, with fixed solar-aspect angle, spin rate, and precession speed, only two free parameters remain: the initial spin phase and the initial precession angle, at the start of science operations. Both angles, and in particular the initial precession angle, can be initialized following various (programmatic) criteria. Examples are optimization/fine-tuning of the Earth-pointing angle, of the number and total duration of Galactic-plane scans, or of the ground-station scheduling. This paper explores various criteria, with particular emphasis on the opportunity to optimise the scanning-law initial conditions to “observe” the most favorable passages of bright stars very close to Jupiter's limb. This would allow a unique determination of the light deflection due to the quadrupole component of the gravitational field of this planet.
Practical relativistic clock synchronization for high-accuracy space astrometry
Authors: Le Poncin-Lafitte Christophe 
Published: January 2010

AbstractFuture high-accuracy space astrometry missions, such as Gaia and SIM, will need a time-tagging of observations consistent with General Relativity nowadays used as standard background for global data processing scheme. In this work, we are focusing on the realization of the onboard time scale. The onboard clock, being not ideal and consequently tainted with systematic biases, has to be carefully calibrated to the ideal relativistic proper time of the satellite. We present here a modeling of this essential step to provide a reliable relation between the onboard time and TCB, a time scale suitable for global data processing.
Lorentz violation and gravity
Authors: Bailey Quentin G. 
Published: January 2010

AbstractIn the last decade, a variety of high-precision experiments have searched for miniscule violations of Lorentz symmetry. These searches are largely motivated by the possibility of uncovering experimental signatures from a fundamental unified theory. Experimental results are reported in the framework called the Standard-Model Extension (SME), which describes general Lorentz violation for each particle species in terms of its coefficients for Lorentz violation. Recently, the role of gravitational experiments in probing the SME has been explored in the literature. In this talk, I will summarize theoretical and experimental aspects of these works. I will also discuss recent lunar laser ranging and atom interferometer experiments, which place stringent constraints on gravity coefficients for Lorentz violation.
Measurement of gravitational time delay using drag-free spacecraft and an optical clock
Authors: Ashby Neil , Bender Peter L. , Hall John L. , Ye Jun , Diddams Scott A. , Jefferts Steven R. , Newbury Nathan , Oates Chris , Dolesi Rita , Vitale Stefano , Weber William J. 
Published: January 2010

AbstractImproved accuracy in measurement of the gravitational time delay of electromagnetic waves passing by the sun may be achieved with two drag-free spacecraft, one with a stable clock and laser transmitter and one with a high-stability transponder. We consider one spacecraft near the Earth-Sun L1 point with an advanced optical clock, and the transponder on a second satellite, which has a 2 year period orbit and eccentricity e = 0.37. Superior conjunctions will occur at aphelion 1, 3, and 5 years after launch of the second spacecraft. The measurements can be made using carrier phase comparisons on the laser beam that would be sent to the distant spacecraft and then transponded back. Recent development of clocks based on optical transitions in cooled and trapped ions or atoms indicate that a noise spectral amplitude of about 5 × 10−15/ at frequencies down to at least 1 microhertz can be achieved in space-borne clocks. An attractive candidate is a clock based on a single laser-cooled Yb+ trapped ion. Both spacecraft can be drag-free at a level of 1×10−13m/s2/ at frequencies down to at least 1 microhertz. The corresponding requirement for the LISA gravitational wave mission is 3 × 10−15m/s2/ at frequencies down to 10−4 Hz, and Gravitational Reference Sensors have been developed to meet this goal. They will be tested in the LISA Pathfinder mission, planned by ESA for flight in 2011. The requirements to extend the performance to longer times are mainly thermal. The achievable accuracy for determining the PPN parameter γ is about 1 × 10−8.
Teaching with Purpose: An Interview with Thomas E. Ludwig
Authors: Ludwig Timothy D. , Ludwig David J. 
Published: January 2010

Thomas E. Ludwig is the John Dirk Werkman Professor of Psychology at Hope College, where he joined the faculty in 1977 after receiving his PhD in development and aging from Washington University in St. Louis. His research focuses on developmental issues in cognitive neuropsychology. He is also the author or coauthor of more than a dozen sets of instructional computer activities, including PsychSim, PsychQuest, PsychOnline, PsychInquiry, Exploring Human Development, ActivePsych, and Concepts in Action. In 2003, Hope College presented him with its Provost's Award for Excellence in Teaching, and in 2005, the American Psychological Foundation honored him with the Charles L. Brewer Distinguished Teaching of Psychology Award. Timothy D. Ludwig received an MA from Wake Forest University and a PhD in industrial/organizational psychology from Virginia Tech. Since 1994, he has been on faculty at Appalachian State University where he has received the University Deans Distinguished Graduate Faculty Award and the UNC Board of Governors Award for Excellence in Teaching. He is currently the editor of the Journal of Organizational Behavior Management and serves on the board of the Organizational Behavior Management National Network. He is the author of dozens of scholarly articles and one book that empirically document the successes of behavioral methods to improve safety and quality in industry. David J. Ludwig is emeritus professor of psychology at Lenoir-Rhyne University. He received an MDiv from Concordia Seminary, in St. Louis, and a PhD in personality from Washington University in St. Louis. His creative blending of psychology and religion has spanned more than 40 years as a university professor, a licensed psychologist, and a Lutheran minister. During this time, he has authored seven books, several DVD series, and numerous professional articles, while speaking internationally on practical ways to develop healthier personal and family relationships.
Exploring spirituality among youth in foster care: findings from the Casey Field Office Mental Health Study
Authors: Jackson Lovie J. , White Catherine Roller , O'Brien Kirk , DiLorenzo Paul , Cathcart Ernie , Wolf Mary , Bruskas Delilah , Pecora Peter J. , Nix‐Early Vivian , Cabrera Jorge 
Published: January 2010

ABSTRACTThis study examined spiritual coping mechanisms, beliefs about spirituality and participation in spiritual activities and in other positive activities among adolescents in foster care. A multidimensional measure of spirituality was developed for face‐to‐face interviews with 188 youth (ages 14–17) from diverse racial/ethnic backgrounds in the United States. Findings revealed 95% of youth believe in God, over 70% believe God is ‘creator’ and God is ‘love’, and 79% considered prayer a spiritual practice. Most youth said love and forgiveness help them heal. Two‐thirds (67%) reported responding to ‘bad or tragic things happening’ by spending time alone, and over half responded by praying (59%) or sharing the problem with someone else (56%). Youth's top three spiritual goals were to follow God's plan for them, become a better person, and know their purpose in life. Based on the value youth ascribed to spiritual coping mechanisms, recommendations for policy and practice focus on the integration of spirituality into practice and caregiving for youth in foster care.
Young people leaving care in Sweden
Authors: Höjer Ingrid , Sjöblom Yvonne 
Published: January 2010

ABSTRACTThe transition from a placement in care to an independent life can be a problematic phase for young people. In Sweden, special care‐leaving services are almost non‐existent. What then happens to young people when they leave a placement in out‐of‐home care? This paper draws on the results of a study in which 16 young care leavers between the ages of 18 and 22 years were interviewed. Telephone interviews were also performed with the young care leavers' parents, social workers, foster carers and institutional staff. The aim of the study was to investigate how young care leavers perceive the transition from care to an independent life. The Swedish welfare model, the prolonged transition to adulthood and the family‐oriented welfare discourse have been used as analytical perspectives. The results show that young care leavers have a pronounced need for social, emotional, practical and financial support. Whilst such support is occasionally provided by foster carers and residential staff, it is seldom given by social services or biological parents. This group is at risk of facing severe problems in the transitional phase from care to independent life, a fact that is not acknowledged by the Swedish welfare system.