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8.0

Jun 27, 2018
06/18

by
Mauro Elías; Francisco D. Mazzitelli

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We analyze critically the renormalization of quantum fields in cosmological spacetimes, using non covariant ultraviolet cutoffs. We compute explicitly the counterterms necessary to renormalize the semiclassical Einstein equations, using comoving and physical ultraviolet cutoffs. In the first case, the divergences renormalize bare conserved fluids, while in the second case it is necessary to break the covariance of the bare theory. We point out that, in general, the renormalized equations differ...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1504.02993

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7.0

Jun 27, 2018
06/18

by
David Brizuela

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The evolution of polar perturbations on a spherical background spacetime is analyzed. The matter content is assumed to be a massless scalar field.This provides a nontrivial dynamics to the background and the linearized equations of motion become much more involved than in the vacuum case. The analysis is performed in a Hamiltonian framework, which makes explicit the dynamical role of each of the variables. After performing a number of canonical transformations, it is possible to completely...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1505.05278

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4.0

Jun 28, 2018
06/18

by
Håkan Andréasson; David Fajman; Maximilian Thaller

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We prove existence of spherically symmetric, static, self-gravitating photon shells as solutions to the massless Einstein-Vlasov system. The solutions are highly relativistic in the sense that the ratio $2m(r)/r$ is close to $8/9$, where $m(r)$ is the Hawking mass and $r$ is the area radius. In 1955 Wheeler constructed, by numerical means, so called idealized spherically symmetric geons, i.e. solutions of the Einstein-Maxwell equations for which the energy momentum tensor is spherically...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1511.01290

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11

Jun 28, 2018
06/18

by
Amare Abebe; Davood Momeni; Ratbay Myrzakulov

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We study a class of shear-free, homogeneous but anisotropic cosmological models with imperfect matter sources in the context of f(R) gravity. We show that the anisotropic stresses are related to the electric part of the Weyl tensor in such a way that they balance each other. We also show that within the class of orthogonal f(R) models, small perturbations of shear are damped, and that the electric part of the Weyl tensor and the anisotropic stress tensor decay with the expansion as well as the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1507.03265

4
4.0

Jun 28, 2018
06/18

by
K. Atazadeh

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We study the quark hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately $10 \mu$ seconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1511.09294

3
3.0

Jun 29, 2018
06/18

by
Sukanta Bose; Sanjeev Dhurandhar; Anuradha Gupta; Andrew Lundgren

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Gravitational wave (GW) signals were recently detected directly by LIGO from the coalescences of two black hole pairs. These detections have strengthened our belief that compact binary coalescences (CBCs) are the most promising GW detection prospects accessible to ground-based interferometric detectors. For detecting CBC signals it is of vital importance to characterize and identify non-Gaussian and non-stationary noise in these detectors. In this work we model two important classes of...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1606.06096

3
3.0

Jun 30, 2018
06/18

by
Abdul Jawad

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This work is based on pilgrim dark energy conjecture which states that phantom-like dark energy possesses the enough resistive force to preclude the formation of black hole. The non-flat geometry is considered which contains the interacting generalized ghost pilgrim dark energy with cold dark matter. Some well-known cosmological parameters (evolution parameter ($\omega_{\Lambda}$) and squared speed of sound) and planes ($\omega_{\Lambda}$-$\omega_{\Lambda}'$ and statefinder) are constructed in...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.4000

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7.0

Jun 26, 2018
06/18

by
Alireza Sepehri; Mir Faizal; Mohammad Reza Setare; Ahmed Farag Ali

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In this paper, we will use a BIonic solution for analyzing the holographic cosmology. A BIonic solution is a configuration of a D3-brane and an anti-D3-brane connected by a wormhole, and holographic cosmology is a recent proposal to explain cosmic expansion by using the holographic principle. In our model, a BIonic configuration will be produced by the transition of fundamental black strings. The formation of a BIonic configuration will cause inflation. As the D3-brane moves away from the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1502.05218

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7.0

Jun 28, 2018
06/18

by
Imanol Albarran; Mariam Bouhmadi-López; Francisco Cabral; Prado Martín-Moruno

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We analyse the quantum behaviour of the "Little Sibling" of the Big Rip singularity (LSBR) [1]. The quantisation is carried within the geometrodynamical approach given by the Wheeler--DeWitt (WDW) equation. The classical model is based on a Friedmann--Lema\^{i}tre--Robertson--Walker Universe filled by a perfect fluid that can be mapped to a scalar field with phantom character. We analyse the WDW equation in two setups. In the first step, we consider the scale factor as the single...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1509.07398

6
6.0

Jun 25, 2018
06/18

by
Wolfgang Muschik; Horst-Heino v. Borzeszkowski

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Starting out with an entropy identity, the entropy flux, the entropy production and the corresponding Gibbs and Gibbs-Duhem equations of general-covariant conti\-nuum thermodynamics are established. Non-dissipative materials and equilibria are investigated. It is proved that equilibrium conditions only put on material properties cannot generate equilibria, rather additionally, the Killing property of the 4-temperature is a necessary condition for space-times in which equilibria are possible.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1501.00554

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5.0

Jun 27, 2018
06/18

by
J. E. Madriz Aguilar; C. Romero; J. B. Fonseca-Neto; T. S. Almeida; J. B. Formiga

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We investigate (2+1)-dimensional gravity in a Weyl integrable spacetime (WIST). We show that, unlike general relativity, this scalar-tensor theory has a Newtonian limit for any dimension and that in three dimensions the congruence of world lines of particles of a pressureless fluid has a non-vanishing geodesic deviation. We present and discuss a class of static vacuum solutions generated by a circularly symmetric matter distribution that for certain values of the parameter w corresponds to a...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1503.04186

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6.0

Jun 27, 2018
06/18

by
Behnam Pourhassan; Ujjal Debnath

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In this paper we consider rotating modified Hayward and rotating modified Bardeen black holes as particle accelerators. We investigate the center of mass energy of two colliding neutral particles with same rest masses falling from rest at infinity to near the horizons of the mentioned black holes. We investigate the range of the particle's angular momentum and the orbit of the particle. We also investigate the center of mass energy for extremal black hole.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1506.03443

3
3.0

Jun 28, 2018
06/18

by
Bethan Cropp; Stefano Liberati; Rodrigo Turcati

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In the analogue gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in a curved spacetime. This description is possible only when the fluid under consideration is barotropic, inviscid and irrotational. In this case, the propagation of the perturbations is governed by an acoustic metric which depends algebrically on the local speed of sound, density and the background flow velocity,...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1512.08198

3
3.0

Jun 29, 2018
06/18

by
Gregory B. Cook; Maxim Zalutskiy

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In this paper, we examine the behavior of modes of the Kerr geometry when the mode's frequency is purely imaginary. We demonstrate that quasinormal modes must be polynomial in nature if their frequency is purely imaginary, and present a method for computing such modes. The nature of these modes, however, is not always easy to determine. Some of the polynomial modes we compute are quasinormal modes. However, some are simultaneously quasinormal modes and total transmission modes, while others...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1607.07406

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8.0

Jun 26, 2018
06/18

by
Manuela G. Rodrigues; Vilson T. Zanchin

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Inspired in a previous work by McClure and Dyer (Classical Quantum Gravity 23, 1971 (2006)), we analyze some solutions of the Einstein-Maxwell equations which were originally written to describe charged black holes in cosmological backgrounds. A detailed analysis of the electromagnetic sources for a sufficiently general metric is performed, and then we focus on deriving the electromagnetic four-current as well as the conserved electric charge of each metric. The charged McVittie solution is...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1502.00688

5
5.0

Jun 27, 2018
06/18

by
Edward Malec; Naqing Xie

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We discuss the relation between the concentration of the Brown-York mass and the formation of trapped surfaces in non-spherical massive systems. In particular, we formulate and prove a precise version of the Thorne hoop conjecture in conformally flat three-geometries sliced by equipotential foliation leaves. An intriguing relationship between the total rest mass and the Brown-York mass is shown. This is a further investigation of the previous work on the Brown-York mass hoop conjecture in...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1503.01354

4
4.0

Jun 27, 2018
06/18

by
Eva Hackmann; Claus Lämmerzahl

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The complete set of analytic solutions of the geodesic equation in a Schwarzschild--(anti-)de Sitter space--time is presented. The solutions are derived from the Jacobi inversion problem restricted to the set of zeros of the theta function, called the theta divisor. In its final form the solutions can be expressed in terms of derivatives of Kleinian sigma functions. The different types of the resulting orbits are characterized in terms of the conserved energy and angular momentum as well as the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1505.07973

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Jun 28, 2018
06/18

by
Christoph Charles; Etera R. Livine

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In the context of the geometrical interpretation of the spin network states of Loop Quantum Gravity, we look at the holonomies of the Ashtekar-Barbero connection on loops embedded in space-like hyperboloids. We use this simple setting to illustrate two points. First, the Ashtekar-Barbero connection is not a space-time connection, its holonomies depend on the spacetime embedding of the canonical hypersurface. This fact is usually interpreted as an inconvenience, but we use it to extract the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1507.00851

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6.0

Jun 27, 2018
06/18

by
Justin Vines; Éanna É. Flanagan

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A point-like object moving in a background black hole spacetime experiences a gravitational self-force which can be expressed as a local function of the object's instantaneous position and velocity, to linear order in the mass ratio. We consider the worldline dynamics defined by the conservative part of the local self-force, turning off the dissipative part, and we ask: Is that dynamical system a Hamiltonian system, and if so, is it integrable? In the Schwarzschild spacetime, we show that the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1503.04727

3
3.0

Jun 30, 2018
06/18

by
Jonathan Ziprick

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We develop a Hamiltonian description of point particles in (2+1)-dimensions using connection and frame-field variables for general relativity. The topology of each spatial hypersurface is that of a punctured two-sphere with particles residing at the punctures. We describe this topology with a CW complex (a collection of two-cells glued together along edges), and use this to fix a gauge and reduce the Hamiltonian. The equations of motion for the fields describe a dynamical triangulation where...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1409.7455

2
2.0

Jun 30, 2018
06/18

by
Christopher J. Fewster; L. H. Ford; Thomas A. Roman

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The probability distributions for the smeared energy densities of quantum fields, in the two and four-dimensional Minkowski vacuum are discussed. These distributions share the property that there is a lower bound at a finite negative value, but no upper bound. Thus arbitrarily large positive energy density fluctuations are possible. In two dimensions we are able to give an exact unique analytic form for the distribution. However, in four dimensions, we are not able to give closed form...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1409.7516

2
2.0

Jun 30, 2018
06/18

by
Lisa Glaser

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To solve the path integral for quantum gravity, one needs to regularise the space-times that are summed over. This regularisation usually is a discretisation, which makes it necessary to give up some paradigms or symmetries of continuum physics. Causal dynamical triangulations regularises the path integral through a simplicial discretisation that introduces a preferred time foliation. The first part of this thesis presents three articles on causal dynamical triangulations. The first article...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1409.8144

2
2.0

Jun 30, 2018
06/18

by
T. P. Shestakova

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In the Batalin - Fradkin - Vilkovisky approach to quantization of gauge theories a principal role is given to the BRST charge which can be constructed as a series in Grassmannian (ghost) variables with coefficients given by generalized structure functions of constraints algebra. Alternatively, the BRST charge can be derived making use of the Noether theorem and global BRST invariance of the effective action. In the case of Yang - Mills fields the both methods lead to the same expression for the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1410.4434

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4.0

Jun 30, 2018
06/18

by
A. A. Grib; Yu. V. Pavlov

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Geodesic completeness needs existence near the horizon of the black hole of "white hole" geodesics coming from the region inside of the horizon. Here we give the classification of all such geodesics with the energies $E/m \le 1$ for the Schwarzschild and Kerr's black hole. The collisions of particles moving along the "white hole" geodesics with those moving along "black hole" geodesics are considered. Formulas for the increase of the energy of collision in the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1410.5736

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2.0

Jun 30, 2018
06/18

by
Prabir Rudra

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In this paper we study the Loop quantum effects on the \textit{Om} diagnostic and subsequently on the universe. We reconstruct the \textit{Om} diagnostic in the background of Loop quantum gravity and then study the behaviour of various Chaplygin gas dark energy models using the modified diagnostic in a comparative scenario. The trajectories discriminate the various dark energy models from each other both in the Einstein gravity as well as Loop quantum gravity. The Loop quantum effects are also...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1410.6709

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2.0

Jun 30, 2018
06/18

by
Alessandra Buonanno; B. S. Sathyaprakash

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Gravitational-wave astronomy will soon become a new tool for observing the Universe. Detecting and interpreting gravitational waves will require deep theoretical insights into astronomical sources. The past three decades have seen remarkable progress in analytical and numerical computations of the source dynamics, development of search algorithms and analysis of data from detectors with unprecedented sensitivity. This Chapter is devoted to examine the advances and future challenges in...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1410.7832

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2.0

Jun 30, 2018
06/18

by
Alexander A. Potapov; Ramil Izmailov; Olga Mikolaychuk; Nikolay Mikolaychuk; Mithun Ghosh; Kamal K. Nandi

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Recently, Harko et al. (2014) derived an approximate metric of the galactic halo in the Eddington inspired Born-Infeld (EiBI) gravity. In this metric, we show that there is an upper limit $\rho _{0}^{\text{upper}}$ on the central density $\rho _{0}$ of dark matter such that stable circular orbits are possible only when the constraint $\rho _{0}\leq \rho_{0}^{\text{upper}}$ is satisfied in each galactic sample. To quantify different $\rho _{0}^{\text{upper}}$ for different samples, we follow the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1412.7897

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5.0

Jun 26, 2018
06/18

by
Dmitry Chirkov; Sergey Pavluchenko; Alexey Toporensky

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In this paper we propose a scheme which allows one to find all possible exponential solutions of special class -- non-constant volume solutions -- in Lovelock gravity in arbitrary number of dimensions and with arbitrate combinations of Lovelock terms. We apply this scheme to (6+1)- and (7+1)-dimensional flat anisotropic cosmologies in Einstein-Gauss-Bonnet and third-order Lovelock gravity to demonstrate how our scheme does work. In course of this demonstration we derive all possible solutions...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1501.04360

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5.0

Jun 26, 2018
06/18

by
Peter K. F. Kuhfittig

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It has been shown that a noncommutative-geometry background may be able to support traversable wormholes. This paper discusses the possible detection of such wormholes in the outer regions of galactic halos by means of gravitational lensing. The procedure allows a comparison to other models such as the Navarro-Frenk-White model and f(R) modified gravity and is likely to favor a model based on noncommutative geometry.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1501.06085

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3.0

Jun 26, 2018
06/18

by
Ayesha Zakria; Mubasher Jamil

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In this paper, we investigate the center of mass energy of the collision for two neutral particles with different rest masses falling freely from rest at infinity in the background of a Kerr-Newman-Taub-NUT black hole. Further, we discuss the center of mass energy near the horizon(s) of an extremal and non-extremal Kerr-Newman-Taub-NUT black hole and show that an arbitrarily high center of mass energy is achievable under some restrictions. We will study the special case of the center of mass...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1501.06306

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6.0

Jun 26, 2018
06/18

by
Petarpa Boonserm; Tritos Ngampitipan; Matt Visser

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We argue that an arbitrary general relativistic static anisotropic fluid sphere, (static and spherically symmetric but with transverse pressure not equal to radial pressure), can nevertheless be successfully mimicked by suitable linear combinations of theoretically attractive and quite simple classical matter: a classical (charged) isotropic perfect fluid, a classical electromagnetic field, and a classical (minimally coupled) scalar field. While the most general decomposition is not unique, a...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1501.07044

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9.0

Jun 26, 2018
06/18

by
Davood Momeni; H. Gholizade; Muhammad Raza; Ratbay Myrzakulov

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Non-local $f(R)$ gravity was proposed as a powerfull alternative to general relativity (GR) . This theory has potentially adverse implications for infrared (IR) regime as well as ultraviolent(UV) early epochs. However, there are a lot of powerful features, making it really user-friendly. A scalar-tensor frame comprising two auxiliary scalar fields, used to reduce complex action. However this is not the case for the modification complex which plays a distinct role in modified theories for...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1502.05000

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3.0

Jun 26, 2018
06/18

by
A. Khodam-Mohammadi; E. Karimkhani; A. Alaei

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The correspondence of the Gauss-Bonnet (GB) and its modification (MGB) models of dark energy with the standard and generalized Chaplygin gas-scalar field models (SCG and GCG) have been studied in a {\deg}at universe. The exact solution of potentials and scalar fields, which describe the accelerated expansion of the universe, are reconstructed. According to the evolutionary behavior of the GB and MGB models, the same form of dynamics of scalar field and potential for different SCG and GCG models...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1502.07832

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5.0

Jun 27, 2018
06/18

by
G. G. L. Nashed

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We apply the energy-momentum tensor which is coordinate independent to calculate the energy content of the axisymmetric solutions. Our results are compared with what have been obtained before within the framework of Einstein general relativity and M{\o}ler's tetrad theory of gravitation.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1503.01379

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4.0

Jun 27, 2018
06/18

by
Ifra Noureen; M. Zubair; A. A. Bhatti; G. Abbas

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The implications of shearfree condition on instability range of anisotropic fluid in $f(R,T)$ are studied in this manuscript. A viable $f(R, T)$ model is chosen to arrive at stability criterion, where $R$ is Ricci scalar and $T$ is the trace of energy momentum tensor. The evolution of spherical star is explored by employing perturbation scheme on modified field equations and contracted Bianchi identities in $f(R, T)$. The effect of imposed shearfree condition on collapse equation and adiabatic...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1504.01251

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7.0

Jun 27, 2018
06/18

by
Bob Osano

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We present a covariant and gauge invariant formalism suited to the study of second-order effects associated with higher order tensor perturbations. The analytical method we have developed enables us to characterize pure second-order tensor perturbations about FLRW model having different kinds of equations of state. Our analysis of the radiation case suggests that it may be feasible to examine the CMB polarization arising from higher order perturbations.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1504.01495

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5.0

Jun 27, 2018
06/18

by
Peter R. Phillips

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We modify the action of Mannheim's conformally invariant model by changing the sign of two coefficients. This breaks conformal symmetry, but results in a cosmology that has a positive effective G and at the same time retains one of the main advantages of the Mannheim model, a possible solution of the cosmological constant problem.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1504.02702

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8.0

Jun 27, 2018
06/18

by
Jan Harms; Ho Jung Paik

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Terrestrial gravity noise, also known as Newtonian noise, produced by ambient seismic and infrasound fields will pose one of the main sensitivity limitations in low-frequency, ground-based, gravitational-wave (GW) detectors. It was estimated that this noise foreground needs to be suppressed by about 3 -- 5 orders of magnitude in the frequency band 10\,mHz to 1\,Hz, which will be extremely challenging. In this article, we present a new approach that greatly facilitates cancellation of gravity...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1504.04724

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5.0

Jun 27, 2018
06/18

by
H. Moradpour; N. Riazi

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We impose perfect fluid concept along with slow expansion approximation to derive new solutions which, considering non-static spherically symmetric metrics, can be treated as Black Holes (BHs). We will refer to these solutions as Quasi BHs. Mathematical and physical features such as Killing vectors, singularities, and mass have been studied. Their horizons and thermodynamic properties have also been investigated. In addition, relationship with other related works (including McVittie's) are...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1505.02188

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Jun 28, 2018
06/18

by
Jonathan Ziprick; Jack Gegenberg

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Beginning from the Ashtekar formulation of canonical general relativity, we derive a physical Hamiltonian written in terms of (classical) loop gravity variables. This is done by gauge-fixing the gravitational fields within a complex of three-dimensional cells such that curvature and torsion vanish within each cell. The resulting theory is holographic, with the bulk dynamics being captured completely by degrees of freedom living on cell boundaries. Quantization is readily obtainable by existing...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1507.07591

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4.0

Jun 28, 2018
06/18

by
S. Asadzadeh; M. S. Khaledian; K. Karami

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Here, we investigate the growth of matter density perturbations as well as the generalized second law (GSL) of thermodynamics in the framework of $f(R)$-gravity. We consider a spatially flat FRW universe filled with the pressureless matter and radiation which is enclosed by the dynamical apparent horizon with the Hawking temperature. For some viable $f(R)$ models containing the Starobinsky, Hu-Sawicki, Exponential, Tsujikawa and AB models, we first explore numerically the evolution of some...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1507.08538

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5.0

Jun 28, 2018
06/18

by
M. Sharif; Rubab Manzoor

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This paper explores hydrodynamics and hydrostatic of a star in post-Newtonian approximation of massive Bran-Dicke gravity. We study approximated solution of the field equations upto $O(c^{-4})$ and generalize Euler equation of motion. We then formulate equations governing hydrodynamics, stability and instability of the system. Finally, we discuss spherically symmetric stars for a specific barptropic case like dust, cosmic string and domain wall in this scenario.

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1508.02306

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6.0

Jun 28, 2018
06/18

by
Ujjal Debnath

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Here we consider static, axially symmetric, rotating and charged Kerr-Sen Dilaton-Axion black hole metric in generalized Boyer-Lindquist coordinates as particle accelerators. We obtain the geodesic motions of particle. We find the effective potential and discuss the circular orbit of a particle. We investigate the center of mass energy of two colliding neutral particles with different rest masses falling from rest at infinity to near the non-extremal horizons (event horizon and Cauchy horizon)...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1508.02385

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5.0

Jun 28, 2018
06/18

by
O. Gurtug; M. Halilsoy

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From inherent non-linearity two gravitational waves, unless they are unidirectional, fail to satisfy a superposition law. They collide to develop a new spacetime carrying the imprints of the incoming waves. Same behaviour is valid also for any massless lightlike field. As a result of the violent collision process either a naked singularity or a Cauchy horizon (CH) develops. It was shown by Chandrasekhar and Xanthopoulos (CX) that a particular class of colliding gravitational waves (CGW)...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1509.05174

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4.0

Jun 28, 2018
06/18

by
M. Kord Zangeneh; M. H. Dehghani; A. Sheykhi

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In this paper, we present a new class of higher dimensional exact topological black hole solutions of the Brans-Dicke theory in the presence of a power-law Maxwell field as the matter source. For this aim, we introduce a conformal transformation which transforms the Einstein-dilaton-power-law Maxwell gravity Lagrangian to the Brans-Dicke-power-law Maxwell theory one. Then, by using this conformal transformation, we obtain the desired solutions. Next, we study the properties of the solutions and...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1509.05990

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2.0

Jun 28, 2018
06/18

by
S. V. Bolokhov; K. A. Bronnikov; P. A. Korolyov; M. V. Skvortsova

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We construct explicit examples of globally regular static, spherically symmetric solutions in general relativity with scalar and electromagnetic fields, describing traversable wormholes with flat and AdS asymptotics and regular black holes, in particular, black universes. (A black universe is a regular black hole with an expanding, asymptotically isotropic space-time beyond the horizon.) Such objects exist in the presence of scalar fields with negative kinetic energy ("phantoms", or...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1510.00546

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2.0

Jun 28, 2018
06/18

by
T. Tahamtan; O. Svitek

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Explicit Robinson--Trautman solutions with electromagnetic field satisfying nonlinear field equations are derived and analyzed. The solutions are generated from the spherically symmetric ones. In all cases the electromagnetic field singularity is removed while the gravitational one persists. The models resolving curvature singularity were not possible to generalize to Robinson--Trautman geometry indicating that the removal of singularity in associated spherically symmetric case is just a...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1510.01183

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4.0

Jun 28, 2018
06/18

by
M. O. Ribas; L. L. Samojeden; F. P. Devecchi; G. M. Kremer

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In this work we investigate a model for the early Universe in a Bianchi type-I metric, where the sources of the gravitational field are a fermionic and a bosonic field, interacting through a Yukawa potential, following the standard model of elementary particles. It is shown that the fermionic field has a negative pressure, while the boson has a small positive pressure. The fermionic field is the responsible for an accelerated regime at early times, but since the total pressure tends to zero for...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1510.01345

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Jun 28, 2018
06/18

by
Kuantay Boshkayev; Hernando Quevedo; Marzhan Abutalip; Zhanerke Kalymova; Sharara Suleymanova

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We investigate equatorial geodesics in the gravitational field of a rotating and deformed source described by the approximate Hartle-Thorne metric. In the case of massive particles, we derive within the same approximation analytic expressions for the orbital angular velocity, the specific angular momentum and energy, and the radii of marginally stable and marginally bound circular orbits. Moreover, we calculate the orbital angular velocity and the radius of lightlike circular geodesics. We...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1510.02016

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2.0

Jun 28, 2018
06/18

by
Martin Kuchynka; Alena Pravdova

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We study the geometrical properties of null congruences generated by an aligned null direction of the Weyl tensor (WAND) in spacetimes of the Weyl and Ricci type N (possibly with a non-vanishing cosmological constant) in an arbitrary dimension. We prove that a type N Ricci tensor and a type III or N Weyl tensor have to be aligned. In such spacetimes, the multiple WAND has to be geodetic. For spacetimes with type N aligned Weyl and Ricci tensors, the canonical form of the optical matrix in the...

Topic: General Relativity and Quantum Cosmology

Source: http://arxiv.org/abs/1510.03562