Date: Thu, 28 Jun 07 00:00:27 GMT Subject: gr-qc daily 9 new + 3 crosses received by eprepget ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ Send any complaints regarding submissions directly to submitter. ------------------------------------------------------------------------------ Point your www client at http://arXiv.org/ To unsubscribe, e-mail To: gr-qc@arXiv.org, Subject: cancel ------------------------------------------------------------------------------ received by eprepget from Tue 26 Jun 07 20:00:19 GMT to Wed 27 Jun 07 20:00:05 GMT ------------------------------------------------------------------------------ \\ arXiv:0706.3934 Date: Tue, 26 Jun 2007 23:01:18 GMT (101kb) Title: Foundations of Relational Dynamics Authors: Edward Anderson Categories: gr-qc Comments: 19 pages and 1 table \\ Relational particle dynamics include the dynamics of pure shape and cases in which absolute scale or absolute rotation are additionally meaningful. These are interesting as regards the absolute versus relative motion debate as well as discussion of conceptual issues connected with the problem of time in quantum gravity. In spatial dimension 1 and 2 the relative configuration spaces of shapes are n-spheres and complex projective spaces, from which knowledge I construct natural mechanics on these spaces. I also show that these coincide with Barbour's indirectly-constructed relational dynamics by performing a full reduction on the latter. Then the identification of the configuration spaces as n-spheres and complex projective spaces, for which spaces much mathematics is available, significantly advances the understanding of Barbour's relational theory in spatial dimensions 1 and 2. I also provide the parallel study of a new theory for which positon and scale are purely relative but orientation is absolute. The configuration space for this is an n-sphere regardless of the spatial dimension, which renders this theory a more tractable arena for investigation of the implications of scale invariance than Barbour's theory itself. \\ ( http://arxiv.org/abs/0706.3934 , 101kb) ------------------------------------------------------------------------------ \\ arXiv:0706.3961 Date: Wed, 27 Jun 2007 06:44:52 GMT (217kb) Title: Extra dimensions and atomic transition frequencies Authors: Li zhigang, Wei-Tou Ni, Antonio Pulido Paton Categories: gr-qc Comments: 8 pages, 1 figure \\ New unification theories predict Large Extra Dimensions (LEDs). If that is the case, gravity would be stronger at short ranges than what Newtonian gravity predicts. LEDs could also have effects at atomic level. In this paper we propose a new method to constrain the size of gravity-only LEDs by analyzing how these LEDs modify the energy of the atomic transitions 1s-2s and 2s-2p (Lamb shift), for the particular case of the hydrogen and muonium atoms. We estimate these effects by using Bethe's non-relativistic treatment of Lamb shift. For the particular case of three LEDs, which may be a candidate to explain the interaction mechanism of dark matter particles, we have found that current knowledge in atomic spectroscopy could constrain their sizes to be less than 10 * 10^(-6) m. Although our contributions do not reach the sensitivity given by SN1987a, they are still slightly better than recent constraints given by Inverse Square Law tests of Eot-Wash group at Washington University, which gave R3 < 36.6 * 10^(-6) m. \\ ( http://arxiv.org/abs/0706.3961 , 217kb) ------------------------------------------------------------------------------ \\ arXiv:0706.3988 Date: Wed, 27 Jun 2007 09:21:22 GMT (8kb) Title: 5-dimensional solution with acceleration and small variation of G Authors: S. B. Fadeev and V. D. Ivashchuk Categories: gr-qc Comments: 4 pages, Latex, prepared for Proc. of the Russian summer school-seminar Modern theoretical problems of gravitation and cosmology, September 9-16, 2007, TSHPU, Kazan-Yalchik, Russia Report-no: IGC-PFUR/2007-06-1fi \\ A 5-dimensional cosmological solution in the model with two 2-forms and two ``phantom'' scalar fields is considered. The model contains two dilatonic coupling vectors obeying certain restrictions. It is shown that there exists a time interval where accelerating expansion of ``our'' 3-dimensional space is compatible with a small value of effective gravitational ``constant'' variation. \\ ( http://arxiv.org/abs/0706.3988 , 8kb) ------------------------------------------------------------------------------ \\ arXiv:0706.3994 Date: Wed, 27 Jun 2007 19:00:57 GMT (37kb) Title: Attractor scenarios and superluminal signals in k-essence cosmology Authors: Jin U Kang, Vitaly Vanchurin, Sergei Winitzki Categories: gr-qc Comments: 27 pages, RevTeX4 \\ Cosmological scenarios with k-essence are invoked in order to explain the observed late-time acceleration of the universe. These scenarios avoid the need for fine-tuned initial conditions (the "coincidence problem") because of the attractor-like dynamics of the k-essence field \phi. It was recently shown that all k-essence scenarios with Lagrangians p=L(X)/\phi^2, necessarily involve an epoch where perturbations of \phi propagate faster than light (the "no-go theorem"). We carry out a comprehensive study of attractor-like cosmological solutions ("trackers") involving a k-essence scalar field \phi and another matter component. The result of this study is a complete classification of k-essence Lagrangians that admit asymptotically stable tracking solutions, among all Lagrangians of the form p=K(\phi)L(X) . Using this classification, we select the class of models that describe the late-time acceleration and avoid the coincidence problem through the tracking mechanism. An analogous "no-go theorem" still holds for this class of models, indicating the existence of a superluminal epoch. In the context of k-essence cosmology, the superluminal epoch does not lead to causality violations. We discuss the implications of superluminal signal propagation for possible causality violations in Lorentz-invariant field theories. \\ ( http://arxiv.org/abs/0706.3994 , 37kb) ------------------------------------------------------------------------------ \\ arXiv:0706.4008 Date: Wed, 27 Jun 2007 12:07:22 GMT (12kb) Title: Conserved Matter Superenergy Currents for Orthogonally Transitive Abelian G2 Isometry Groups Authors: Ingemar Eriksson Categories: gr-qc Comments: 15 pages \\ In a previous paper we showed that the electromagnetic superenergy tensor, the Chevreton tensor, gives rise to a conserved current when there is a hypersurface orthogonal Killing vector present. In addition, the current is proportional to the Killing vector. The aim of this paper is to extend this result to the case when we have a two-parameter Abelian isometry group that acts orthogonally transitive on non-null surfaces. It is shown that for four-dimensional Einstein-Maxwell theory with a source-free electromagnetic field, the corresponding superenergy currents lie in the orbits of the group and are conserved. A similar result is also shown to hold for the trace of the Chevreton tensor and for the Bach tensor, and also in Einstein-Klein-Gordon theory for the superenergy of the scalar field. This links up well with the fact that the Bel tensor has these properties and the possibility of constructing conserved mixed currents between the gravitational field and the matter fields. \\ ( http://arxiv.org/abs/0706.4008 , 12kb) ------------------------------------------------------------------------------ \\ arXiv:0706.4010 Date: Wed, 27 Jun 2007 12:15:53 GMT (10kb) Title: Quantum toy model for black-hole back-reaction Authors: Clovis Maia and Ralf Sch\"utzhold Categories: gr-qc Comments: 4 pages \\ We propose a simple quantum field theoretical toy model for black hole evaporation and study the back-reaction of Hawking radiation onto the classical background. It turns out that the horizon is also ``pushed back'' in this situation (i.e., the interior region shrinks) but this back-reaction is not caused by energy conservation but by momentum balance. The effective heat capacity and the induced entropy variation can have both signs -- depending on the parameters of the model. PACS: 04.62.+v, 04.70.Dy. \\ ( http://arxiv.org/abs/0706.4010 , 10kb) ------------------------------------------------------------------------------ \\ arXiv:0706.4039 Date: Wed, 27 Jun 2007 14:55:24 GMT (402kb) Title: Study of Quantum Gravity Effects in INTEGRAL Gamma-Ray Bursts Authors: Raphael Lamon, Nicolas Produit, Frank Steiner Categories: gr-qc Comments: 11 pages, 24 figures, submitted to A&A \\ We search for possible time lags caused by quantum gravitational (QG) effects using gamma-ray bursts detected by INTEGRAL. The advantage of this satellite is that we have at our disposal the energy and arrival time of every single photon, which enhances the precision of the time resolution. We present a new method for seeking time lags in unbinned data using a maximum likelihood and support our conclusions with Monte Carlo simulations. These simulations show that today's satellites are not apt to measure effects at the order of the Planck mass. However, a naive analysis of the data shows a mass scale well below the expected one. Only by correcting for internal time lags are we able to give a lower bound on the quantum gravitation mass scale that is in accordance with predictions. \\ ( http://arxiv.org/abs/0706.4039 , 402kb) ------------------------------------------------------------------------------ \\ arXiv:0706.4043 Date: Wed, 27 Jun 2007 14:59:44 GMT (10kb) Title: Frame Dependence in Scalar-tensor Theory Authors: Mark D. Roberts Categories: gr-qc Comments: 12 pages \\ Palatini variation of Jordan frame lagrangians gives an equation relating the dilaton to the object of non-metricity and hence the existence of the dilaton implies that the spacetime connection is more general than that given soley by the Christoffel symbol of general relativity. Transferring from Jordan to Einstein frame, which connection, lagrangian, field equations and stress conservation equations occur are discussed: it is found that the Jordan frame has more information, this can be expressed in several ways, the simplest is that the extra information corresponds to the function multiplying the Ricci scalar in the action. The Einstein frame has the advantages that stress conservation implies no currents and that the field equations are easier to work with. This is illustrated by application to Robertson-Walker spacetime. \\ ( http://arxiv.org/abs/0706.4043 , 10kb) ------------------------------------------------------------------------------ \\ arXiv:0706.4057 Date: Wed, 27 Jun 2007 15:49:39 GMT (43kb) Title: An angular momentum bound at null infinity Authors: Piotr T. Chru\'sciel and Paul Tod Categories: gr-qc \\ We prove an inequality relating the trace of the extrinsic curvature, the total angular momentum, the centre of mass, and the Trautman-Bondi mass for a class of gravitational initial data sets with constant mean curvature extending to null infinity. As an application we obtain non-existence results for the asymptotic Dirichlet problem for CMC hypersurfaces in stationary space-times. \\ ( http://arxiv.org/abs/0706.4057 , 43kb) %-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%- ------------------------------------------------------------------------------ \\ arXiv:0704.3618 (*cross-listing*) Date: Thu, 26 Apr 2007 20:10:24 GMT (231kb) Title: Astrophysical Accretion as an Analogue Gravity Phenomena Authors: Tapas Kumar Das Categories: astro-ph gr-qc Comments: 56 pages, 11 figures, revtex4. Send email request to the author for high resolution version of the manuscript \\ In recent years, strong analogies have been established between the physics of acoustic perturbations in an inhomogeneous dynamical fluid system, and some kinematic features of space-time in general relativity. An effective metric, referred to as the `acoustic metric', which describes the geometry of the manifold in which acoustic perturbations propagate, can be constructed. This effective geometry can capture the properties of curved space-time in general relativity. Physical models constructed utilizing such analogies are called `analogue gravity models'. Classical analogue gravity effect may be observed when acoustic perturbations propagate through a inhomogeneous transonic classical fluid. The acoustic horizon, which resembles a black hole event horizon in many ways, is generated at the transonic point in the fluid flow. The acoustic horizon is essentially a null hyper surface, generators of which are the acoustic null geodesics, i.e. the phonons. The acoustic horizon emits acoustic radiation with quasi thermal phonon spectra, which is analogous to the actual Hawking radiation. The temperature of the radiation emitted from the acoustic horizon is referred to as the analogue Hawking temperature. It has been demonstrated that, in general, the transonic accretion in astrophysics can be considered as an example of the classical analogue gravity model naturally found in the Universe. \\ ( http://arxiv.org/abs/0704.3618 , 231kb) ------------------------------------------------------------------------------ \\ arXiv:0706.3700 (*cross-listing*) Date: Mon, 25 Jun 2007 20:00:33 GMT (32kb) Title: Probing white dwarf interiors with LISA: periastron precession in eccentric double white dwarfs Authors: B. Willems (1), A. Vecchio (1,2), V. Kalogera (1) ((1) Northwestern U., (2) U. of Birmingham) Categories: astro-ph gr-qc Comments: Submitted \\ In globular clusters, dynamical interactions give rise to a population of eccentric double white dwarfs detectable by the Laser Interferometer Space Antenna (LISA) up to the Large Magellanic Cloud. In this Letter, we explore the detectability of periastron precession in these systems with LISA. Unlike previous investigations, we consider contributions due to tidal and rotational distortions of the binary components in addition to general relativistic contributions to the periastron precession. At orbital frequencies above a few mHz, we find that tides and stellar rotation dominate, opening up a possibly unique window to the study of the interior and structure of white dwarfs. \\ ( http://arxiv.org/abs/0706.3700 , 32kb) ------------------------------------------------------------------------------ \\ arXiv:0706.3730 (*cross-listing*) Date: Tue, 26 Jun 2007 18:32:28 GMT (484kb) Title: Narrowing Constraints with Type Ia Supernovae: Converging on a Cosmological Constant Authors: Scott Sullivan (UC Irvine), Asantha Cooray (UC Irvine), Daniel E. Holz (LANL) Categories: astro-ph gr-qc hep-th Comments: 16 pages, 6 figures, submitted to JCAP; A code to estimate binned & uncorrelated w(z) estimates from the supernovae Hubble diagram and most other cosmological data available from http://www.cooray.org/sn.html \\ We apply a parameterization-independent approach to fitting the dark energy equation-of-state (EOS). Utilizing the latest type Ia supernova data, combined with results from the cosmic microwave background and baryon acoustic oscillations, we find that the dark energy is consistent with a cosmological constant. We establish independent estimates of the evolution of the dark energy EOS by diagonalizing the covariance matrix. We find three independent constraints, which taken together imply that the equation of state is more negative than -0.2 at the 68% confidence level in the redshift range 0 1.2 and rolls to a value of -1 today, and ``thawing'' models where the EOS is near -1 at high redshifts, but rapidly evolves to values greater than -0.85 at z < 0.2. Finally, we propose a parameterization-independent figure-of-merit, to help assess the ability of future surveys to constrain dark energy. While previous figures-of-merit presume specific dark energy parameterizations, we suggest a binning approach to evaluate dark energy constraints with a minimum number of assumptions. \\ ( http://arxiv.org/abs/0706.3730 , 484kb) %%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%% ------------------------------------------------------------------------------ \\ arXiv:0704.0221 (*cross-listing*) replaced with revised version Wed, 27 Jun 2007 19:04:44 GMT (7kb) Title: The Return of a Static Universe and the End of Cosmology Authors: Lawrence M. Krauss (1,2) and Robert J. Scherrer (2) ((1) Case Western Reserve University, (2) Vanderbilt University) Categories: astro-ph gr-qc hep-ph hep-th Comments: 5th prize 2007 Gravity Research Foundation Essay Competition, to appear, GRG October 2007; typos corrected; references updated \\ ( http://arxiv.org/abs/0704.0221 , 7kb) ------------------------------------------------------------------------------ \\ arXiv:0704.1058 replaced with revised version Tue, 26 Jun 2007 23:57:24 GMT (48kb) Title: Dark energy, gravitation and supernovae Authors: Pilar Ruiz-Lapuente Categories: gr-qc astro-ph hep-ph Comments: Invited Topical Review (Class. Quan. Grav) 27 pages Journal link: http://stacks.iop.org/0264-9381/24/R91 Journal-ref: Class. Quantum. Grav. 24 R91 (June 7 2007) \\ ( http://arxiv.org/abs/0704.1058 , 48kb) ------------------------------------------------------------------------------ \\ arXiv:0705.0827 (*cross-listing*) replaced with revised version Wed, 27 Jun 2007 18:40:37 GMT (12kb) Title: A Metric for Gradient RG Flow of the Worldsheet Sigma Model Beyond First Order Authors: T Oliynyk, V Suneeta, E Woolgar Categories: hep-th gr-qc math.DG Comments: 15 pages; references added, this version matches the version to be published (Phys Rev D) \\ ( http://arxiv.org/abs/0705.0827 , 12kb) ------------------------------------------------------------------------------ \\ arXiv:0706.0205 replaced with revised version Wed, 27 Jun 2007 17:38:27 GMT (17kb) Title: Remarks on initial conditions for scalar field driven inflationary models Authors: D.H. Coule Categories: gr-qc hep-th Comments: 22pages slight corrections made, further refs \\ ( http://arxiv.org/abs/0706.0205 , 17kb) ------------------------------------------------------------------------------ \\ arXiv:astro-ph/0702478 (*cross-listing*) replaced with revised version Wed, 27 Jun 2007 08:18:47 GMT (148kb) Title: Toward a Unified Description of Dark Energy and Dark Matter from the Abnormally Weighting Energy Hypothesis Authors: A. Fuzfa, J.-M. Alimi Categories: astro-ph gr-qc Comments: 17 pages, 13 figures; version 3: one references added, matches version published in Phys. Rev. D Journal-ref: Phys. Rev. D 75, 123007 (2007) DOI: 10.1103/PhysRevD.75.123007 \\ ( http://arxiv.org/abs/astro-ph/0702478 , 148kb) ------------------------------------------------------------------------------ \\ arXiv:gr-qc/0702039 replaced with revised version Wed, 27 Jun 2007 09:06:22 GMT (172kb) Title: Upper limits on gravitational wave emission from 78 radio pulsars Authors: The LIGO Scientific Collaboration: B. Abbott, et al, M. Kramer and A. G. Lyne Categories: gr-qc astro-ph Comments: 21 pages, accepted for Phys. Rev. D Report-no: LIGO-P060011-05-Z \\ ( http://arxiv.org/abs/gr-qc/0702039 , 172kb) ------------------------------------------------------------------------------ \\ arXiv:gr-qc/0702048 replaced with revised version Wed, 27 Jun 2007 14:40:55 GMT (24kb) Title: Two alternative Dirac equations with gravitation Authors: Mayeul Arminjon Categories: gr-qc Comments: 28 pages. v3: additional explanations, wording improvements, a few misprints corrected, references added. v2: redactional improvements (specially introduction), references added \\ ( http://arxiv.org/abs/gr-qc/0702048 , 24kb) ------------------------------------------------------------------------------ \\ arXiv:gr-qc/0702097 replaced with revised version Wed, 27 Jun 2007 12:16:16 GMT (30kb) Title: Metric gravity theories and cosmology. I. Physical interpretation and viability Authors: Leszek M. Sokolowski Categories: gr-qc Comments: 29 pages. The previous version is divided in two separate papers. The first four chapters, expanded and modified, form the present paper. The title and abstract are adequately modified, some recent references added. The main conclusions remain unchanged. The second part will also appear in Class. Qu. Grav Journal-ref: Class. Quantum Grav. 24 (2007) 3391-3411 DOI: 10.1088/0264-9381/24/13/015 \\ ( http://arxiv.org/abs/gr-qc/0702097 , 30kb) ------------------------------------------------------------------------------ \\ arXiv:gr-qc/0703152 replaced with revised version Wed, 27 Jun 2007 09:30:08 GMT (66kb) Title: Binary system delays and timing noise in searches for gravitational waves from known pulsars Authors: Matthew Pitkin and Graham Woan (University of Glasgow) Categories: gr-qc astro-ph Comments: 10 pages, 11 figures, accepted by Phys. Rev. D Report-no: LIGO-P060063-02-Z \\ ( http://arxiv.org/abs/gr-qc/0703152 , 66kb) %%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%--- For subscribe options to combined physics archives, e-mail To: physics@arXiv.org, Subject: subscribe ----------------------------------------------------------------------------- For help on viewing and making submissions, see http://arXiv.org/help/ For a list of archive mirror sites, see http://arXiv.org/servers.html ----------------------------------------------------------------------------- Third-party submissions cause excessive problems. Author self-submissions are exceedingly preferred. E-mail submissions have been discontinued in favor of better support for Web submissions. See http://arXiv.org/help/uploads