Date: Fri, 30 Sep 11 00:09:15 GMT Subject: gr-qc daily 11 new + 4 crosses received by eprepget ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ Send any comments regarding submissions directly to submitter. ------------------------------------------------------------------------------ Archives at http://arxiv.org/ To unsubscribe, e-mail To: gr-qc@arXiv.org, Subject: cancel ------------------------------------------------------------------------------ received by eprepget from Wed 28 Sep 11 20:00:00 GMT to Thu 29 Sep 11 20:00:00 GMT ------------------------------------------------------------------------------ \\ arXiv:1109.6317 Date: Wed, 28 Sep 2011 12:12:14 GMT (623kb,D) Title: Observational constraints in scalar tensor theory with tachyonic potential Authors: H. Farajollahi, A. Salehi, A. Shahabi Categories: gr-qc Comments: 16 pages, 19 figures, Will be published in JCAP \\ We study the dynamics of the scalar tensor cosmological model in the presence of tachyon field. In an alternative approach, in two exponential and power law form of the scalar field functions in the model, field equations are solved by simultaneously best fitting the model parameters with the most recent observational data. This approach gives us an observationally verified interpretation of the dynamics of the universe. We then discuss the best fitted of equation of state parameter, the statefinder parameters and the reconstructed scalar field in the model. \\ ( http://arxiv.org/abs/1109.6317 , 623kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6324 Date: Wed, 28 Sep 2011 20:00:03 GMT (9kb) Title: Black holes in scalar-tensor gravity Authors: Thomas P. Sotiriou, Valerio Faraoni Categories: gr-qc astro-ph.HE hep-th Comments: 4 pages \\ Hawking has proven that black holes which are stationary as the endpoint of gravitational collapse in Brans--Dicke theory (without a potential) are no different than in general relativity. We extend this proof to the much more general class of scalar-tensor and f(R) gravity theories, without assuming any additional symmetries. \\ ( http://arxiv.org/abs/1109.6324 , 9kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6358 Date: Tue, 27 Sep 2011 16:28:15 GMT (830kb,D) Title: Stability analysis and Observational Measurement in Chameleonic Generalised Brans--Dicke Cosmology Authors: H.Farajollahi, A. Salehi Categories: gr-qc Comments: 15 pages, 18 figures Journal-ref: JCAP 07(2011)036 DOI: 10.1088/1475-7516/2011/07/036 \\ We investigate the dynamics of the chameleonic Generalised Brans--Dicke model in flat FRW cosmology. In a new approach, a framework to study stability and attractor solutions in the phase space is developed for the model by simultaneously best fitting the stability and model parameters with the observational data. The results show that for an accelerating universe the phantom crossing does not occur in the past and near future. \\ ( http://arxiv.org/abs/1109.6358 , 830kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6469 Date: Thu, 29 Sep 2011 10:45:33 GMT (17kb) Title: Thermodynamics of viscous Matter and Radiation in Early Universe Authors: A. Tawfik (Egyptian Ctr. Theor. Phys., Cairo) and H. Magdy (Egyptian Ctr. Theor. Phys., Cairo) Categories: gr-qc Comments: 9 pages, 2 figures (3 eps graphs) Report-no: ECTP-2011-04 \\ Assuming that the background geometry is filled with free gas consisting of matter and radiation and no phase transitions being occurred in the early Universe, we discuss the thermodynamics of this {\it closed} system using classical approaches. We find that essential cosmological quantities, such as Hubble parameter $H$, scale factor $a$ and curvature parameter $k$, can be derived from this simple model, which on one hand fulfills and entirely obeys the laws of thermodynamics. On the other hand, the results are compatible with the Friedmann-Lemaitre-Robertson-Walker model and the Einstein field equations. The inclusion of finite bulk viscosity coefficient derives to important changes in all these cosmological quantities. Accordingly, our picture about the evolution of the Universe and its astrophysical consequences seems to be a subject of a radical revision. We find that $k$ strongly depends on the thermodynamics of background matter. The time scale, at which negative curvature might take place, depends on the relation between the matter content and the total energy. Using quantum and statistical approaches, we assume that the size of the Universe is given by the volume occupied one particle and one photon. Different types of their interactions are taken into account. Expressions for $H$ and $a$ are introduced. Therefore, the expansion of the Universe turns to be accessible. \\ ( http://arxiv.org/abs/1109.6469 , 17kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6538 Date: Thu, 29 Sep 2011 14:25:42 GMT (60kb,D) Title: Lorentzian spinfoam propagator Authors: Eugenio Bianchi and You Ding Categories: gr-qc Comments: 13 pages \\ The two-point correlation function is calculated in the Lorentzian EPRL spinfoam model, and shown to match with the one in Regge calculus in a proper limit: large boundary spins, and small Barbero-Immirzi parameter, keeping the size of the quantum geometry finite and fixed. Compared to the Euclidean case, the definition of a Lorentzian boundary state involves a new feature: the notion of past- and future-pointing intertwiners. The semiclassical correlation function is obtained for a time-oriented semiclassical boundary state. \\ ( http://arxiv.org/abs/1109.6538 , 60kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6563 Date: Thu, 29 Sep 2011 15:40:14 GMT (15kb) Title: Particle propagation and effective space-time in Gravity's Rainbow Authors: Remo Garattini and Gianluca Mandanici Categories: gr-qc hep-th Comments: RevTeX 4, 11 pages \\ Basing on the results obtained in a our previous study on Gravity's Rainbow, we determine the quantum corrections to the space-time metric for the Schwarzschild and the de Sitter background, respectively. We analyze how quantum fluctuations alter these metrics inducing modifications on the propagation of test particles. Significantly enough we find that quantum corrections can become relevant not only for particles approaching the Planck energy but, due to the one loop contribution, even for low-energy particles as far as Planckian length scales are considered. We briefly compare our results with others obtained in similar studies and with the recent experimental OPERA announcement of superluminal neutrino propagation. \\ ( http://arxiv.org/abs/1109.6563 , 15kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6576 Date: Thu, 29 Sep 2011 16:13:36 GMT (887kb) Title: On the stability of scalar-vacuum space-times Authors: K.A. Bronnikov, J.C. Fabris, A. Zhidenko Categories: gr-qc astro-ph.CO hep-th Comments: 17 pages, 5 figures \\ We study the stability of static, spherically symmetric solutions to the Einstein equations with a scalar field as the source. We describe a general methodology of studying small radial perturbations of scalar-vacuum configurations with arbitrary potentials $V(\phi)$, and in particular space-times with throats (including wormholes), which are possible if the scalar is phantom. At such a throat, the effective potential for perturbations $V_{eff}$ is known to have a positive pole (a potential wall) that prevents a complete perturbation analysis. We show that, generically, (i) $V_{eff}$ has precisely the form required for regularization by the known S-deformation method, and (ii) a solution with the regularized potential leads to regular scalar field and metric perturbations of the initial configuration. As a particular example, we prove the instability of all static solutions with both normal and phantom scalars and $V(\phi) \equiv 0$, under spherically symmetric perturbations. We thus confirm the previous results on the unstable nature of anti-Fisher wormholes and Fisher's singular solution and prove the instability of other branches of these solutions including the anti-Fisher "cold black holes". \\ ( http://arxiv.org/abs/1109.6576 , 887kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6577 Date: Thu, 29 Sep 2011 16:15:22 GMT (33kb) Title: Statistical Mechanics of Wormholes Authors: Paul H. Cox, Benjamin C. Harms, Shaoqi Hou Categories: gr-qc hep-th Comments: 8 pages, 1 figure \\ The statistical mechanics of a gas of Einstein-Kalb-Ramond wormholes is studied in this paper. The wormholes studied are the result of sewing together two Reissner-Nordstrom-type black hole metrics at their horizons. By requiring the stress-energy tensor associated with this geometry to be that of a Kalb-Ramond field, we obtain the mass and Kalb-Ramond `charge` of the wormholes in terms of the parameters describing the mass density, tension and pressure. We investigate the statistical mechanics of this system of wormholes within the context of the statistical bootstrap model. A gas of such wormholes is found to obey the bootstrap condition only for an extreme, non-thermodynamic, energy and `charge` distribution among the particles. We comment briefly on the scattering of quantum wormholes. \\ ( http://arxiv.org/abs/1109.6577 , 33kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6612 Date: Thu, 29 Sep 2011 18:27:58 GMT (195kb) Title: The creation of radiation and the relict of inflaton potential Authors: Yu-Chung Chen Categories: gr-qc hep-th Comments: 24 pages, 2 figures \\ Recently, we have performed a research about solving the cosmological constant problem. Our scenario is based on the "non-reheating" assumption of inflationary theory, and taking the viewpoint of thermodynamics to be our device. We discover that radiation could be viewed as the production of the interaction between the moving inflaton {phi} and the "effective kinetic frictional force" of the oscillating system of {phi}. According to the concept of "effective frictional force", we obtain two results of accelerated expansion. One is that the universe will enter the mode of slowly and uniformly rolling {phi} to begin its accelerating expansion, where radiation will be created continuously during the accelerating expansion epoch. The other is that the inflaton potential will be survived as the relict, V(phi(t_r)), caused by the "effective static frictional force" which forms the "stagnant zone" of {phi}. Then, we find the exact solution of V(phi(t)) and provide our proof to show that V(phi(t))=V(phi(t_r)) when t>= t_r (where {phi} is at rest after time t_r), which means that the relict is equal to the effective cosmological constant {Lambda} which appears in Friedman equations. \\ ( http://arxiv.org/abs/1109.6612 , 195kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6627 Date: Wed, 28 Sep 2011 07:20:18 GMT (548kb) Title: Thermodynamics of a Bardeen black hole in noncommutative space Authors: M. Sharif and Wajiha Javed Categories: gr-qc Comments: 17 pages, 9 figures, accepted for publication in Canadian J. Physics \\ In this paper, we examine the effects of space noncommutativity on the thermodynamics of a Bardeen charged regular black hole. For a suitable choice of sets of parameters, the behavior of the singularity, horizon, mass function, black hole mass, temperature, entropy and its differential, area and energy distribution of the Bardeen solution have been discussed graphically for both noncommutative and commutative spaces. Graphs show that the commutative coordinates extrapolate all such quantities (except temperature) for a given set of parameters. It is interesting to mention here that these sets of parameters provide the singularity (essential for $r_h>0$) and horizon ($f(r_h)=0$ for $r_h>0$) for the black hole solution in noncommutative space, while for commutative space no such quantity exists. \\ ( http://arxiv.org/abs/1109.6627 , 548kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6636 Date: Thu, 29 Sep 2011 19:33:50 GMT (181kb) Title: Contrasting features of anisotropic loop quantum cosmologies: the role of spatial curvature Authors: Brajesh Gupt, Parampreet Singh Categories: gr-qc Comments: 26 pages, 3 figures \\ A characteristic feature of loop quantization of the isotropic and Bianchi-I spacetimes is the existence of universal bounds on the energy density and the expansion and shear scalars, independent of the matter content. In this work, we investigate the properties of these physical quantities in the Bianchi-II and Bianchi-IX spacetimes which have been recently loop quantized using the connection operator approach. Using the effective Hamiltonian approach, we show that energy density and the expansion and shear scalars turn out to be bounded, albeit not by universal values. In contrast to the isotropic and Bianchi-I models, there are important differences in the way underlying quantum geometry effects lead to these bounds. In particular, the role of energy conditions and the inverse triad modifications are shown to be significant. These results bring out subtle physical distinctions between the quantization using holonomies over closed loops performed for isotropic and Bianchi-I models and the connection operator approach. We find that qualitative differences in physics exist for these quantization methods even for the isotropic models in the presence of spatial curvature. As an illustration, we show that, unlike the holonomy based quantization, the expansion scalar in the effective spacetime description corresponding to the connection operator approach is unbounded for isotropic spatially closed and open models. \\ ( http://arxiv.org/abs/1109.6636 , 181kb) %-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%-%- ------------------------------------------------------------------------------ \\ arXiv:1011.2291 (*cross-listing*) Date: Wed, 10 Nov 2010 08:12:37 GMT (224kb) Date (revised v2): Thu, 29 Sep 2011 05:04:40 GMT (370kb) Title: The effect of higher derivative correction on $\eta /s$ and conductivities in STU model Authors: J. Sadeghi, B. Pourhassan and A. R. Amani Categories: hep-th gr-qc Comments: revised version \\ In this paper we study the ratio of shear viscosity to entropy, electrical and thermal conductivities for the R-charged black hole in STU model. We generalize previous works to the case of a black hole with three different charges. Actually we use diffusion constant to obtain ratio of shear viscosity to entropy. By applying the thermodynamical stability we recover previous results. Also we investigate the effect of higher derivative corrections. \\ ( http://arxiv.org/abs/1011.2291 , 370kb) ------------------------------------------------------------------------------ \\ arXiv:1109.4915 (*cross-listing*) Date: Thu, 22 Sep 2011 18:56:12 GMT (20kb) Date (revised v2): Thu, 29 Sep 2011 17:36:02 GMT (21kb) Title: Possible solution to the main cosmological constant problem Authors: V. Emelyanov, F.R. Klinkhamer Categories: hep-th gr-qc Comments: 26 pages, v2: minor changes Report-no: KA-TP-23-2011 \\ A particular model of two massless vector fields and standard relativistic matter is presented. The vector fields dynamically cancel an effective cosmological constant of arbitrary magnitude and sign. Flat Minkowski spacetime appears as the limit of attractor-type solutions of the model field equations. Asymptotically, the model field equations give rise to both a standard Friedmann-Robertson-Walker universe and the standard Newtonian dynamics for matter density perturbations on small (non-cosmological) scales. \\ ( http://arxiv.org/abs/1109.4915 , 21kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6329 (*cross-listing*) Date: Wed, 28 Sep 2011 20:00:22 GMT (82kb,D) Title: Tidal disruption rate of stars by spinning supermassive black holes Authors: Michael Kesden Categories: astro-ph.CO gr-qc Comments: 9 pages, 4 figures, submitted to PRD \\ A supermassive black hole can disrupt a star when its tidal field exceeds the star's self-gravity, and can directly capture stars that cross its event horizon. For black holes with mass M > 10^7 solar masses, tidal disruption of main-sequence stars occurs close enough to the event horizon that a Newtonian treatment of the tidal field is no longer valid. The fraction of stars that are directly captured is also no longer negligible. We calculate generically oriented stellar orbits in the Kerr metric, and evaluate the relativistic tidal tensor at pericenter for those stars not directly captured by the black hole. We combine this relativistic analysis with previous calculations of how these orbits are populated to determine tidal-disruption rates for spinning black holes. We find, consistent with previous results, that black-hole spin increases the upper limit on the mass of a black hole capable of tidally disrupting solar-like stars to ~7 x 10^8 solar masses. More quantitatively, we find that direct stellar capture reduces tidal-disruption rates by a factor 2/3 (1/10) at M = 10^7 (10^8) solar masses. The strong dependence of tidal-disruption rates on black-hole spin for M > 10^8 solar masses implies that future surveys like LSST that discover thousands of tidal disruption events can constrain supermassive black-hole spin demographics. \\ ( http://arxiv.org/abs/1109.6329 , 82kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6588 (*cross-listing*) Date: Wed, 28 Sep 2011 06:26:12 GMT (2179kb) Title: Dispersion Modes of Hot Plasma for Schwarzschild de-Sitter Horizon in a Veselago Medium Authors: M. Sharif and Ifra Noureen Categories: physics.gen-ph gr-qc Comments: 22 pages, 8 figures, accepted for publication in Canadian J. Physics. arXiv admin note: text overlap with arXiv:1101.0884 \\ We analyze the dispersion modes of hot plasma around Schwarzschild de-Sitter event horizon in the presence of Veselago medium. For this purpose, we apply ADM 3+1 formalism to develop GRMHD equations for the Schwarzschild de-Sitter spacetime. Implementation of linear perturbation yields perturbed GRMHD equations that are used for the Fourier analysis of rotating (non-magnetized and magnetized) plasma. Wave analysis is described by the graphical representation of the wave vector, refractive index, change in refractive index, phase and group velocities. The outcome of this work supports the validity of Veselago medium. \\ ( http://arxiv.org/abs/1109.6588 , 2179kb) %%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%%--%% ------------------------------------------------------------------------------ \\ arXiv:1006.1902 (*cross-listing*) replaced with revised version Thu, 29 Sep 2011 19:23:47 GMT (28kb) Title: Wilsonian Approach to Fluid/Gravity Duality Authors: Irene Bredberg, Cynthia Keeler, Vyacheslav Lysov, Andrew Strominger Categories: hep-th gr-qc Comments: 34 pages, harvmac, clarified boundary condition Journal-ref: JHEP 03(2011):141 DOI: 10.1007/JHEP03(2011)141 \\ ( http://arxiv.org/abs/1006.1902 , 28kb) ------------------------------------------------------------------------------ \\ arXiv:1102.1062 replaced with revised version Wed, 28 Sep 2011 20:05:30 GMT (72kb) Title: The spherical symmetry Black hole collapse in expanding universe Authors: J. T. Firouzjaee Categories: gr-qc astro-ph.GA Comments: 7 pages, 3 figures \\ ( http://arxiv.org/abs/1102.1062 , 72kb) ------------------------------------------------------------------------------ \\ arXiv:1104.1463 (*cross-listing*) replaced with revised version Thu, 29 Sep 2011 04:31:42 GMT (19kb) Title: Tensor models and 3-ary algebras Authors: Naoki Sasakura Categories: hep-th gr-qc math-ph math.MP Comments: 21 pages, no essential changes of contents, but explanations added for clarity Report-no: YITP-11-45 \\ ( http://arxiv.org/abs/1104.1463 , 19kb) ------------------------------------------------------------------------------ \\ arXiv:1104.2040 (*cross-listing*) replaced with revised version Wed, 28 Sep 2011 21:27:52 GMT (753kb) Title: Constraining holographic inflation with WMAP Authors: Richard Easther, Raphael Flauger, Paul McFadden and Kostas Skenderis Categories: astro-ph.CO gr-qc hep-th Comments: 24 pages, 9 figs, published version Journal-ref: JCAP 09(2011)030 DOI: 10.1088/1475-7516/2011/09/030 \\ ( http://arxiv.org/abs/1104.2040 , 753kb) ------------------------------------------------------------------------------ \\ arXiv:1108.3040 (*cross-listing*) replaced with revised version Thu, 29 Sep 2011 16:50:32 GMT (480kb) Title: Inflation driven by particle creation Authors: Saulo Carneiro Categories: astro-ph.CO gr-qc hep-th Comments: Some discussions and references added \\ ( http://arxiv.org/abs/1108.3040 , 480kb) ------------------------------------------------------------------------------ \\ arXiv:1109.4458 (*cross-listing*) replaced with revised version Thu, 29 Sep 2011 15:08:48 GMT (18kb) Title: A Complete Classification of Higher Derivative Gravity in 3D and Criticality in 4D Authors: Nobuyoshi Ohta Categories: hep-th gr-qc Comments: 20 pages, v2: minor corrections, refs. added, v3: logic modified Report-no: KU-TP 052 \\ ( http://arxiv.org/abs/1109.4458 , 18kb) ------------------------------------------------------------------------------ \\ arXiv:1109.5221 replaced with revised version Thu, 29 Sep 2011 01:04:29 GMT (165kb) Title: Nonexistence of quasinormal modes in the extremal BTZ black hole Authors: Yun Soo Myung, Yong-Wan Kim, Young-Jai Park Categories: gr-qc hep-th Comments: 13 pages, 2 figures, references added \\ ( http://arxiv.org/abs/1109.5221 , 165kb) ------------------------------------------------------------------------------ \\ arXiv:1109.5872 replaced with revised version Thu, 29 Sep 2011 15:57:07 GMT (703kb) Title: Geodesically Complete Universe Authors: Itzhak Bars Categories: gr-qc hep-th math-ph math.MP Comments: 11 pages, 9 figures, LaTeX \\ ( http://arxiv.org/abs/1109.5872 , 703kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6160 (*cross-listing*) replaced with revised version Thu, 29 Sep 2011 15:34:45 GMT (7kb) Title: The OPERA neutrino velocity result and the synchronisation of clocks Authors: Carlo R. Contaldi Categories: hep-ph astro-ph.CO gr-qc Comments: 3 pages, added reference and expanded some comments \\ ( http://arxiv.org/abs/1109.6160 , 7kb) ------------------------------------------------------------------------------ \\ arXiv:1109.6249 replaced with revised version Thu, 29 Sep 2011 15:32:20 GMT (446kb) Title: Environmental fifth-force hypothesis for the OPERA superluminal neutrino phenomenology: constraints from orbital motions around the Earth Authors: Lorenzo Iorio Categories: gr-qc astro-ph.EP hep-ph physics.space-ph Comments: LaTex2e, 16 pages, no tables, 5 figures. Previously uncited reference now cited in the text. Link to the CERN conference added in footnote 1. Comment in the conclusions added \\ ( http://arxiv.org/abs/1109.6249 , 446kb) %%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%---%%%--- 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