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2.0
Jun 29, 2018
06/18
by
Jarmo Mäkelä
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We point out that with a specific counting of states loop quantum gravity implies that black holes perform a phase transition at a certain characteristic temperature $T_C$. In this phase transition the punctures of the spin network on the stretched horizon of the black hole jump, in effect, from the vacuum to the excited states. The characteristic temperature $T_C$ may be regarded as the lowest possible temperature of the hole. From the point of view of a distant observer at rest with respect...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1604.01393
2
2.0
Jun 30, 2018
06/18
by
Luca Fabbri; Stefano Vignolo
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In this paper, the recently-introduced ELKO and the well-known Dirac spinor fields will be compared; however, instead of comparing them under the point of view of their algebraic properties or their dynamical features, we will proceed by investigating the analogies and similarities in terms of their geometrical character viewed from the perspective of torsion. The paper will be concluded by sketching some consequences for the application to cosmology and particle physics.
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1407.8237
2
2.0
Jun 30, 2018
06/18
by
Ran Li; Junkun Zhao
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eye 2
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It has been shown that the mass of the scalar field in the charged stringy black hole is never able to generate a potential well outside the event horizon to trap the superradiant modes. This is to say that the charged stringy black hole is stable against the massive charged scalar perturbation. In this paper we will study the superradiant instability of the massless scalar field in the background of charged stringy black hole due to a mirror-like boundary condition. The analytical expression...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1403.7279
2
2.0
Jun 30, 2018
06/18
by
Tomasz Pawłowski
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A simple idea of relating the LQG and LQC degrees of freedom is discussed in context of toroidal Bianchi I model. The idea is an expansion of the construction originally introduced by Ashtekar and Wilson-Ewing and relies on explicit averaging of certain sub-class of spin-networks over the subgroup of the diffeomorphisms remaining after the gauge fixing used in homogeneous LQC. It is based on the set of clearly defined principles, thus is a convenient tool to control the emergence and behavior...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1411.0323
3
3.0
Jun 30, 2018
06/18
by
Ming Chen; Yong-Chang Huang
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We first review some aspects of gravitational wave and the thermodynamic expression of Einstein field equations, these achieved conclusions allow people to think of Einstein's gravitational wave as a kind of sound wave in ordinary gas which propagates as an adiabatic compression wave. In the following, using the properties of photon gas in "white wall box", we find an analogous relationship between ordinary gas and photon gas through sound velocity formula. At last, by taking the...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1402.5767
2
2.0
Jun 28, 2018
06/18
by
Jaume de Haro
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Background boucing cosmologies in the framework of General Relativity, driven by a single scalar field filling the Universe, and with a quasi-matter domination period, i.e., depicting the so-called Matter Bounce Scenario, are reconstructed for geometries with positive spatial curvature. These cosmologies lead to a nearly flat power spectrum of the curvature fluctuations in co-moving coordinates for modes that leave the Hubble radius during the quasi-matter domination period, and whose spectral...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1511.05048
2
2.0
Jun 29, 2018
06/18
by
S. H. Hendi; M. S. Talezadeh
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Regarding the wide applications of dilaton gravity in the presence of electrodynamics, we introduce a suitable Lagrangian for the coupling of dilaton with gauge field. There are various Lagrangians which show the coupling between scalar fields and electrodynamics with correct special situations. In this paper, taking into account conformal transformation of Brans-Dicke theory with an electrodynamics Lagrangian, we show that how scalar field should couple with electrodynamics in dilaton gravity....
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1605.00456
3
3.0
Jun 29, 2018
06/18
by
H. S. Vieira; V. B. Bezerra
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We apply the confluent Heun functions to study the resonant frequencies (quasispectrum), the Hawking radiation and the scattering process of scalar waves, in a class of spacetimes, namely, the ones generated by a Kerr-Newman-Kasuya spacetime (dyon black hole) and a Reissner-Nordstr\"{o}m black hole surrounded by a magnetic field (Ernst spacetime). In both spacetimes, the solutions for the angular and radial parts of the corresponding Klein-Gordon equations are obtained exactly, for massive...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1603.02233
3
3.0
Jun 30, 2018
06/18
by
Hector J. Hortua; Leonardo Castañeda
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Nowdays, Cosmological Perturbation Theory is a standard and useful tool in theoretical cosmology. In this work, we compare the 1+3 covariant formalism in perturbation theory (Ellis et al.) to the gauge invariant approach (Bruni et al.), and we show the equivalence of these formalisms to fix the choice of the perturbed variables (gauge choice) in magnetogenesis. We analyze the evolution of primordial magnetic fields through perturbation theory and we discuss the similarities and differences...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1407.5551
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7.0
Jun 30, 2018
06/18
by
I. Brito; J. Carot; F. C. Mena; E. G. L. R. Vaz
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The Einstein field equations are derived for a static cylindrically symmetric spacetime with elastic matter. The equations can be reduced to a system of two nonlinear ordinary differential equations and we present analytical and numerical solutions satisfying the dominant energy conditions. Furthermore, we show that the solutions can be matched at a finite radius to suitable $\Lambda$-vacuum exteriors given by the Linet-Tian spacetime.
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1403.5684
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5.0
Jun 30, 2018
06/18
by
U. Camci
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In this paper, we study Noether gauge symmetries of geodesic motion for geodesic Lagrangian of four classes of metrics of G\"{o}del-type spacetimes for which we calculated the Noether gauge symmetries for all classes I-IV, and find the first integrals of corresponding classes to derive a complete characterization of the geodesic motion. Using the obtained expressions for $\dot{t}, \dot{r}, \dot{\phi}$ and $\dot{z}$ of each classes I-IV which depends essentially on two independent...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1404.4270
4
4.0
Jun 30, 2018
06/18
by
A. A. Garcia Diaz; G. Gutierrez Cano
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In this report a detailed derivation of the dynamical equations for an n dimensional heterotic string theory of the Horowitz type is carried out in the string frame and in the Einstein frame too. In particular, the dynamical equations of the three dimensional string theory are explicitly given. The relation of the Horowitz Welch and Horne Horowitz string black hole solution is exhibited. The Chan Mann charged dilaton solution is derived and the subclass of string solutions field is explicitly...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1412.5618
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11
Jun 28, 2018
06/18
by
Sourav Haldar; Sudipto Bhattacharjee; Subenoy Chakraborty
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The paper deals with an extensive study of the Unified First Law (UFL) in the Freidmann-Robertson-Walker space-time model. By projecting the UFL along the Kodama vector one can always obtain the second Friedmann equation. Also studying the UFL on the event horizon it is found that clausius relation cannot be obtained from the Unified First Law by projecting it along the tangent to the event horizon as it can be for the trapping horizon. However, it is shown in the present work that clausius...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1508.05090
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12
Jun 28, 2018
06/18
by
Hans-Peter Gittel; Jacek Jezierski; Jerzy Kijowski
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This paper deals with the generalization of usual round spheres in the flat Minkowski spacetime to the case of a generic four-dimensional spacetime manifold $M$. We consider geometric properties of sphere-like submanifolds in $M$ and introduce conditions on external curvature and torsion, which lead to a definition of a {\em rigid sphere}. The main result is a local existence theorem concernig such spheres. For this purpose we apply the surjective implicit function theorem. The proof is based...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1508.07872
7
7.0
Jun 29, 2018
06/18
by
Abdul Jawad; Shamaila Rani
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eye 7
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We explore wormhole solutions in a non-minimal torsion-matter coupled gravity by taking an explicit non-minimal coupling between the matter Lagrangian density and an arbitrary function of torsion scalar. This coupling depicts the transfer of energy and momentum between matter and torsion scalar terms. The violation of null energy condition occurred through effective energy-momentum tensor incorporating the torsion-matter non-minimal coupling while normal matter is responsible for supporting the...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1612.02042
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13
Jun 27, 2018
06/18
by
Leonard Parker
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eye 13
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Quantum creation processes during the very rapid early expansion of the universe are believed to give rise to temperature anisotropies and polarization patterns in the CMB radiation. These have been observed by satellites such as COBE, WMAP, and PLANCK, and by bolometric instruments placed near the South Pole by the BICEP collaborations. The expected temperature anisotropies are well-confirmed. The B-mode polarization patterns in the CMB are currently under measurement jointly by the PLANCK and...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1503.00359
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12
Jun 27, 2018
06/18
by
José-María Ibáñez; Isabel Cordero-Carrión; Miguel-Ángel Aloy; José-María Martí; Juan-Antonio Miralles
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eye 12
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We analyze the influence of the magnetic field in the convexity properties of the relativistic magnetohydrodynamics system of equations. To this purpose we use the approach of Lax, based on the analysis of the linearly degenerate/genuinely non-linear nature of the characteristic fields. Degenerate and non-degenerate states are discussed separately and the non-relativistic, unmagnetized limits are properly recovered. The characteristic fields corresponding to the material and Alfv\'en waves are...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1503.00978
4
4.0
Jun 29, 2018
06/18
by
D. A. Tretyakova; T. M. Adyev
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eye 4
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We examine observational signatures of the asymptotically de Sitter branch of static spherically symmetric Horndeski/Galileon solutions. Our analysis reveales that possible deviations of the photon sphere size from those of the GR Schwarzshild solution are vanishing compared to the resolution of modern radio-interferometric observations. These deviations are heavily suppressed by the bounds coming from the weak-field observation. We conclude that shadow size would not be a useful characteristic...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1610.07300
2
2.0
Jun 29, 2018
06/18
by
Lydia Bieri; Piotr T. Chruściel
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eye 2
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comment 0
We present the argument that the past limit of the Trautman-Bondi mass is the ADM mass under weak hypotheses on the decay of the metric towards spatial infinity, without any smallness conditions on the initial data, assuming well defined energy, momentum, center of mass and angular moment. Part of the proof consists of a careful inspection of the proof of stability of Minkowski space-time, which is sketched. This is complemented by an interior gluing result for asymptotically flat initial data...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1612.04359
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6.0
Jun 29, 2018
06/18
by
Naoki Tsukamoto; Yungui Gong
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eye 6
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Compact objects with a light sphere such as black holes and wormholes can reflect light rays like a mirror. This gravitational lensing phenomenon is called retrolensing and it is an interesting tool to survey dark and compact objects with a light sphere near the solar system. In this paper, we calculate the deflection angle analytically in the strong deflection limit in the Reissner-Nordstrom spacetime without Taylor expanding it in the power of the electric charge. Using the obtained...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1612.08250
5
5.0
Jun 29, 2018
06/18
by
Alain Dirkes
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eye 5
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In this article we present a particular theory of gravity in which Einstein's field equations are modified by promoting Newton's constant $G$ to a covariant differential operator $G_\Lambda(\Box_g)$. The general idea was obviously outlined for the first time in [13-16] and originates from the quest of finding a mechanism that is able to degravitate the vacuum energy on cosmological scales. We suggest in this manuscript a precise covariant coupling model which acts like a high-pass filter with a...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1607.04123
3
3.0
Jun 29, 2018
06/18
by
S. D. Maharaj; D. Kileba Matondo; P. Mafa Takisa
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Several new families of exact solution to the Einstein-Maxwell system of differential equations are found for anisotropic charged matter. The spacetime geometry is that of Finch and Skea which satisfies all criteria for physical acceptability. The exact solutions can be expressed in terms of elementary functions, Bessel functions and modified Bessel functions. When a parameter is restricted to be an integer then the special functions reduce to simple elementary functions. The uncharged model of...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1612.08523
2
2.0
Jun 29, 2018
06/18
by
Francisco Frutos-Alfaro; Michael Soffel
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eye 2
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Among the known exact solutions of Einsteins vacuum field equations the Manko-Novikov and the Quevedo-Mashhoon metrics might be suitable ones for the description of the exterior gravitational field of some real non-collapsed body. By means of the Fodor-Hoenselaers-Perjes formalism we computed the lowest ten relativistic multipole moments of these metrics. Corresponding moments were derived for the static vacuum solutions of Gutsunayev-Manko and Hernandez-Martin. A direct comparison between the...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1606.07173
2
2.0
Jun 30, 2018
06/18
by
M. R. Setare; V. Kamali
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eye 2
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In this paper we study non-abelian gauge field inflation (gauge-flation) model in the context of intermediate and logamediate scenario. Important parameters of this model are presented for these two cases. Numerical study shows that the intermediate and logamediate gauge-flation are compatible with WMAP9 observational data. For intermediate inflation, where the cosmological scale factor expands as: $a(t)=a_0\exp(At^f)$ ($A>0, 01, A>0$), $N\geq 200$ and $\lambda=2$ cases lead to...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1401.1400
4
4.0
Jun 30, 2018
06/18
by
Nicolas Sanchis-Gual; Juan Carlos Degollado; Pedro J. Montero; José A. Font
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eye 4
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Recent perturbative studies have shown the existence of long-lived, quasi-stationary configurations of scalar fields around black holes. In particular, such configurations have been found to survive for cosmological timescales, which is a requirement for viable dark matter halo models in galaxies based on such type of structures. In this paper we perform a series of numerical relativity simulations of dynamical non-rotating black holes surrounded by self-gravitating scalar fields. We solve...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1412.8304
2
2.0
Jun 30, 2018
06/18
by
Vijay Varma; Parameswaran Ajith; Sascha Husa; Juan Calderon Bustillo; Mark Hannam; Michael Puerrer
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eye 2
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We study the effect of non-quadrupolar modes in the detection and parameter estimation of gravitational waves (GWs) from non-spinning black-hole binaries. We evaluate the loss of signal-to-noise ratio and the systematic errors in the estimated parameters when one uses a quadrupole-mode template family to detect GW signals with all the relevant modes, for target signals with total masses $20 M_\odot \leq M \leq 250 M_\odot$ and mass ratios $1 \leq q \leq 18$. Target signals are constructed by...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1409.2349
2
2.0
Jun 29, 2018
06/18
by
Jingbo Wang
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eye 2
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In this paper, we analysis the counter-term for the general relativity in the Palatini framework. The expression is valid for both the null boundary and non-null boundary. We show that final results coincide with that in Ref.\cite{pad1} which starts form the Einstein-Hilbert action.
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1609.00443
2
2.0
Jun 29, 2018
06/18
by
James Healy; Carlos O. Lousto
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eye 2
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We present the results of 61 new simulations of nonprecessing spinning black hole binaries with mass ratios $q=m_1/m_2$ in the range $1/3\leq q\leq1$ and individual spins covering the parameter space $-0.85\leq\alpha_{1,2}\leq0.85$. We additionally perform 10 new simulations of nonspinning black hole binaries with mass ratios covering the range $1/6\leq q
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1610.09713
4
4.0
Jun 30, 2018
06/18
by
Nicolas Sanchis-Gual; Pedro J. Montero; Jose A. Font; Ewald Mueller; Thomas W. Baumgarte
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We adopt a reference-metric approach to generalize a covariant and conformal version of the Z4 system of the Einstein equations. We refer to the resulting system as ``fully covariant and conformal", or fCCZ4 for short, since it is well suited for curvilinear as well as Cartesian coordinates. We implement this fCCZ4 formalism in spherical polar coordinates under the assumption of spherical symmetry using a partially-implicit Runge-Kutta (PIRK) method and show that our code can evolve both...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1403.3653
2
2.0
Jun 29, 2018
06/18
by
Jie-Xiong Mo; Gu-Qiang Li; Xiao-Bao Xu
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eye 2
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In this paper, we investigate the thermodynamics of higher-dimensional $f(R)$ black holes in the extended phase space. Both the analytic expressions and numerical results for the possible critical physical quantities are obtained. It is proved that meaningful critical specific volume only exists when $p$ is odd. This unique phenomenon may be attributed to the combined effect of $f(R)$ gravity and conformally invariant Maxwell field. It is also shown that the ratio $P_cv_c/T_c$ differs from that...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1609.06422
2
2.0
Jun 30, 2018
06/18
by
Lau Loi So
texts
eye 2
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For describing the non-negative gravitational energy-momentum in terms of a pure Bel-Robinson type energy-momentum in a quasi-local 2-surface, both the Bel-Robinson tensor $B$ and tensor $V$ are suitable. We have found that this Bel-Robinson type energy-momentum can be modified such that it satisfies the Lorentz covariant, future pointing and non-spacelike properties. We find that these particular quasi-local energy-momentum properties can be obtained from (i): $B$ or $V$ plus a tensor $S$ in a...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1405.7883
2
2.0
Jun 29, 2018
06/18
by
M. Zubair; Farzana Kousar; Sebastian Bahamonde
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eye 2
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First and second laws of black hole thermodynamics are examined at the apparent horizon of FRW spacetime in $f(R,R_{\alpha\beta}R^{\alpha\beta} ,\phi)$ gravity, where $R$, $R_{\alpha\beta}R^{\alpha\beta}$ and $\phi$ are the Ricci scalar, Ricci invariant and the scalar field respectively. In this modified theory, Friedmann equations are formulated for any spatial curvature. These equations can be presented into the form of first law of thermodynamics for $T_{h}d\hat{S}_{h}+...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1604.07213
3
3.0
Jun 30, 2018
06/18
by
Sam R. Dolan; Patrick Nolan; Adrian C. Ottewill; Niels Warburton; Barry Wardell
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eye 3
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We extend the gravitational self-force approach to encompass `self-interaction' tidal effects for a compact body of mass $\mu$ on a quasi-circular orbit around a black hole of mass $M \gg \mu$. Specifically, we define and calculate at $O(\mu)$ (conservative) shifts in the eigenvalues of the electric- and magnetic-type tidal tensors, and a (dissipative) shift in a scalar product between their eigenbases. This approach yields four gauge-invariant functions, from which one may construct other...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1406.4890
3
3.0
Jun 28, 2018
06/18
by
Shao-Wen Wei; Yu-Xiao Liu; Chun-E Fu
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In this paper, the null geodesics and gravitational lensing in a nonsingular spacetime are investigated. According to the nature of the null geodesics, the spacetime is divided into several cases. In the weak deflection limit, we find the influence of the nonsingularity parameter $q$ on the positions and magnifications of the images is negligible. In the strong deflection limit, the coefficients and observables for the gravitational lensing in a nonsingular black hole background and a weakly...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1510.02560
3
3.0
Jun 28, 2018
06/18
by
Nilanjana Mahata; Subenoy Chakraborty
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eye 3
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In Friedman-Robertson-Walker flat spacetime, we consider a three fluid cosmological model which contains dark matter, dark energy and baryonic matter in the form of perfect fluid with a barotropic equation of state. Dark matter is taken in form of dust and dark energy is described by a scalar field with a potential $V(\phi)$. Einstein's field equations are reduced to an autonomous dynamical system by suitable redefinition of basic variables. Considering exponential potential for the scalar...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1512.07017
2
2.0
Jun 29, 2018
06/18
by
Alan Coley; Daniele Gregoris; Woei Chet Lim
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eye 2
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Using the Geroch transformation we obtain the first example of an exact stiff fluid spike solution to the Einstein field equations in a closed form exhibiting a spacelike $G_1$ group of symmetries (i.e., with a single isometry). This new solution is of Petrov type I and exhibits a spike crossing which persists to the past, which allows us to better understand spike crossings in the context of structure formation.
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1606.07177
2
2.0
Jun 30, 2018
06/18
by
Inyong Cho; Naveen K. Singh
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We investigate inflation and its scalar perturbation driven by a massive scalar field in the unimodular theory of gravity. We introduce a parameter $\xi$ with which the theory is invariant under general unimodular coordinate transformations. When the unimodular parameter is $\xi=6$, the classical picture of inflation is reproduced in the unimodular theory because it recovers the background equations of the standard theory of general relativity. We show that for $\xi=6$, the theory is equivalent...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1412.6205
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4.0
Jun 29, 2018
06/18
by
Yi Liao; Xiao-Bo Gong; Jian-Sheng Wu
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eye 4
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For a Kerr black hole (KBH) with spin $J$ and mass $M$ in a steady electromagnetic field, a special Wald vacuum solution (WVS) has been found in the case of no-source uniform field. For WVS, the Meissner effect (ME) occurs only in the the extreme KBH where $M^2/J=1$, in this case, the magnetic field is totally excluded from the event horizon (EH) of KBH. However, WVS does not consider the Hawking radiation (HR) but treats KBH as an absolutely black body. If HR is added , researchers believe...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1609.00636
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3.0
Jun 30, 2018
06/18
by
Peter Zimmerman; Eric Poisson
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eye 3
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The gravitational self-force has thus far been formulated in background spacetimes for which the metric is a solution to the Einstein field equations in vacuum. While this formulation is sufficient to describe the motion of a small object around a black hole, other applications require a more general formulation that allows for a nonvacuum background spacetime. We provide a foundation for such extensions, and carry out a concrete formulation of the gravitational self-force in two specific...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1406.5111
3
3.0
Jun 30, 2018
06/18
by
Subenoy Chakraborty; Subhajit Saha
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eye 3
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The paper deals with Hawking radiation from both a general static black hole and a nonstatic spherically symmetric black hole. In case of static black hole, tunnelling of nonzero mass particles is considered and due to complicated calculations, quantum corrections are calculated only up to the first order. The results are compared with those for massless particles near the horizon. On the other hand, for dynamical black hole, quantum corrections are incorporated using the Hamilton-Jacobi method...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1702.06991
3
3.0
Jun 30, 2018
06/18
by
Nandan Roy; Narayan Banerjee
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eye 3
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The stability criteria for the generalized Brans-Dicke cosmology in a spatially flat, homogeneous and isotropic cosmological model is discussed in the presence of a perfect fluid. The generalization comes through the channel that the Brans-Dicke coupling parameter $\omega$ is allowed to be a function of the scalar field $\phi$. This generalization can lead to a host of scalar-tensor theories of gravity for various choices of $\omega = \omega (\phi)$. A very interesting general result has been...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1702.02169
3
3.0
Jun 30, 2018
06/18
by
Meng-Sen Ma; Ren Zhao
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eye 3
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We show by explicit computations that there is a superficial inconsistency between the conventional first law of black hole thermodynamics and Bekenstein-Hawking area law for three types of regular black holes. The corrected form of the first law for these regular black holes is given. The derivation relies on the general structure of the energy-momentum tensor of the matter fields. When the black hole mass parameter $M$ is included in the energy-momentum tensor, the conventional form of the...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1411.0833
2
2.0
Jun 29, 2018
06/18
by
David Anderson; Nicolas Yunes; Enrico Barausse
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eye 2
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Certain scalar-tensor theories of gravity that generalize Jordan-Fierz-Brans-Dicke theory are known to predict non-trivial phenomenology for neutron stars. In these theories, first proposed by Damour and Esposito-Far\`ese, the scalar field has a standard kinetic term, and couples conformally to the matter fields. The weak equivalence principle is therefore satisfied, but scalar effects may arise in strong-field regimes, e.g. allowing for violations of the strong equivalence principle in neutron...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1607.08888
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3.0
Jun 29, 2018
06/18
by
Jibitesh Dutta; Wompherdeiki Khyllep; Erickson Syiemlieh
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eye 3
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In the evolution of late universe, the main source of matter are Dark energy and Dark matter. They are indirectly detected only through their gravitational manifestations. So the possibility of interaction with each other without violating observational restrictions is not ruled out. With this motivation, we investigate the dynamics of DGP braneworld where source of dark energy is a scalar field and it interacts with matter source. Since observation favours phantom case more, we have also...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1602.03329
2
2.0
Jun 28, 2018
06/18
by
A. V. Astashenok; S. D. Odintsov
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eye 2
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Realistic models of neutron and quark stars in the framework of mimetic gravity with Lagrange multiplier constraint are presented. We discuss the effect of mimetic scalar aiming to describe dark matter on mass-radius relation and the moment of inertia for slowly rotating relativistic stars. The mass-radius relation and moment of inertia depend on the value of mimetic scalar in the center of star. This fact leads to the ambiguity in the mass-radius relation for a given equation of state. {Such...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1512.07279
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2.0
Jun 30, 2018
06/18
by
Shahar Hod
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We study analytically a black-hole-ring system which is composed of a stationary axisymmetric ring of particles in orbit around a perturbed Kerr black hole of mass $M$. In particular, we calculate the shift in the orbital frequency of the innermost stable circular orbit (ISCO) due to the finite mass $m$ of the orbiting ring. It is shown that for thin rings of half-thickness $r\ll M$, the dominant finite-mass correction to the characteristic ISCO frequency stems from the self-gravitational...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1404.1566
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3.0
Jun 30, 2018
06/18
by
F. Contreras; N. Cruz; G. Palma
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We present an exact analytical bouncing solution for a closed universe filled with only one exotic fluid with negative pressure, obeying a Generalized Equations of State (GEoS) of the form $P(\rho)=A\rho+B\rho^{\lambda}$, where $A$, $B$ and $\lambda$ are constants. In our solution $A=-1/3$ and $\lambda=1/2$ and $B
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1701.03438
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5.0
Jun 28, 2018
06/18
by
Filip Ficek
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In this paper I study stationary, spherically symmetric accretion of fluids onto a charged black hole in the presence of the cosmological constant. For some isothermal equations of state it is possible to obtain analytic solutions. In the case of a radiation fluid I point out a connection between locations of the horizons and the sonic (critical) points. In specific cases the solutions form closed, binoculars-like trajectories in a phase diagram of the velocity vs. radius.
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1509.07005
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5.0
Jun 30, 2018
06/18
by
Norbert Bodendorfer; Andreas Schäfer; John Schliemann
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Chamseddine and Mukhanov recently proposed a modified version of general relativity that implements the idea of a limiting curvature. In the spatially flat, homogeneous, and isotropic sector, their theory turns out to agree with the effective dynamics of the simplest version of loop quantum gravity if one identifies their limiting curvature with a multiple of the Planck curvature. At the same time, it extends to full general relativity without any symmetry assumptions and thus provides an ideal...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1703.10670
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3.0
Jun 28, 2018
06/18
by
Filip Hejda; Jiří Bičák
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We briefly summarise the basic properties of spacetimes representing rotating, charged black holes in strong axisymmetric magnetic fields. We concentrate on extremal cases, for which the horizon surface gravity vanishes. We investigate their properties by finding simpler spacetimes that exhibit their geometries near degenerate horizons. Employing the simpler geometries obtained by near-horizon limiting description we analyse the Meissner effect of magnetic field expulsion from extremal black...
Topic: General Relativity and Quantum Cosmology
Source: http://arxiv.org/abs/1510.00301
