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M. R. Setare

Publications and source records attributed to M. R. Setare.

At least 127 records · Page 7Linked to original sources
arXiv2011

Holographic superconductors in a model of non-relativistic gravity

We have studied holographic superconductors with spherical symmetry in the Ho$\check{\textbf{r}}$ava-Lifshitz gravity by using a semi analytical method, and also we have calculated the critical temperature and shown when the condensation will appear in a similar pattern as in the Einstein-Gauss- Bonnet gravity. We have computed the dependency of the conductivity as a function of frequency in this new non-relativistic model of quantum gravity.

hep-th↗
arXiv2011

Thermodynamics of viscous dark energy in an RSII braneworld

We show that for an RSII braneworld filled with interacting viscous dark energy and dark matter, one can always rewrite the Friedmann equation in the form of the first law of thermodynamics, $dE=T_hdS_h+WdV$, at apparent horizon. In addition, the generalized second law of thermodynamics can fulfilled in a region enclosed by the apparent horizon on the brane for both constant and time variable 5-dynamical Newton's constant $G_5$. These results hold regardless of the specific form of the dark energy. Our study further support that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.

physics.gen-ph↗
arXiv2011

Viscous dark energy and generalized second law of thermodynamics

We examine the validity of the generalized second law of thermodynamics in a non-flat universe in the presence of viscous dark energy. At first we assume that the universe filled only with viscous dark energy. Then, we extend our study to the case where there is an interaction between viscous dark energy and pressureless dark matter. We examine the time evolution of the total entropy, including the entropy associated with the apparent horizon and the entropy of the viscous dark energy inside the apparent horizon. Our study show that the generalized second law of thermodynamics is always protected in a universe filled with interacting viscous dark energy and dark matter in a region enclosed by the apparent horizon. Finally, we show that the the generalized second law of thermodynamics is fulfilled for a universe filled with interacting viscous dark energy and dark matter in the sense that we take into account the Casimir effect.

physics.gen-ph↗
arXiv2011

Generalized Massive Gravity and Galilean Conformal Algebra in two dimensions

Galilean conformal algebra (GCA) in two dimensions arises as contraction of two copies of the centrally extended Virasoro algebra ($t\rightarrow t, x\rightarrowεx$ with $ε\rightarrow 0$). The central charges of GCA can be expressed in term of Virasoro central charges. For finite and non-zero GCA central charges, the Virasoro central charges must behave as asymmetric form $O(1)\pm O(\frac{1}ε)$. We propose that, the bulk description for 2d GCA with asymmetric central charges is given by general massive gravity (GMG) in three dimensions. It can be seen that, if the gravitational Chern-Simons coupling $\frac{1}μ$ behaves as of order O($\frac{1}ε$) or ($μ\rightarrowεμ$), the central charges of GMG have the above $ε$ dependence. So, in non-relativistic scaling limit $μ\rightarrowεμ$, we calculated GCA parameters and finite entropy in term of gravity parameters mass and angular momentum of GMG.

hep-th↗
arXiv2011

Holographic description of Kerr-Bolt-AdS-dS Spacetimes

We show that there exists a holographic 2D CFT description of a Kerr-Bolt-AdS-dS spacetime. We first consider the wave equation of a massless scalar field propagating in extremal Kerr-Bolt-AdS-dS spacetimes and find in the "near region", the wave equation in extremal limit could be written in terms of the $SL(2,R)$ quadratic Casimir. This suggests that there exist dual CFT descriptions of these black holes. In the probe limit, we compute the scattering amplitudes of the scalar off the extremal black holes and find perfect agreement with the CFT prediction. Furthermore we study the holographic description of the generic four dimensional non-extremal Kerr-Bolt-AdS-dS black holes. We find that if focusing on the near-horizon region, for the massless scalar scattering in the low-frequency limit, the radial equation could still be rewritten as the $SL(2,R)$ quadratic Casimir, suggesting the existence of dual 2D description. We read the temperatures of the dual CFT from the conformal coordinates and obtain the central charges by studying the near-horizon geometry of near-extremal black holes. We recover the macroscopic entropy from the microscopic counting. We also show that for the superradiant scattering, the retarded Green's functions and the corresponding absorption cross sections are in perfect match with CFT prediction.

hep-th↗
arXiv2011

Hidden Conformal Symmetry of Rotating Black Holes in Minimal Five-Dimensional Gauged Supergravity

In the present paper we show that for a low frequency limit the wave equation of massless scalar field in the background of non-extremal charged rotating black holes in five-dimensional minimal gauged and ungauged supergravity can be written as the Casimir of an $SL(2,R)$ symmetry, our result show that the entropy of the black hole is reproduced by the Cardy formula, also the absorption cross section is in consistence with the finite temperature absorption cross section for a 2D CFT.

hep-th↗
arXiv2010

Holographic Q-Picture of Black Holes in Five Dimensional Minimal Supergravity

In this article, we explore the holographic Q-picture description for the charged rotating black holes in the five-dimensional minimal supergravity. The central charge in the Q-picture depends only on black hole charge, therefore can be computed from the near horizon geometry of the extremal and non-rotating counterpart. Moreover, the CFT temperatures can be identified by studying the hidden conformal symmetry, and the related gravity-CFT dictionary can be translated via thermodynamics analysis. The entropy and absorption cross section computed from both gravity and CFT sides properly agree with each other.

hep-th↗
arXiv2010

Cardy-Verlinde formula of Kehagias-Sfetsos black hole

In this paper, we have shown that the entropy of the Kehagias-Sfetsos black hole in Ho$\check{\textbf{r}}$ava-Lifshitz (HL) gravity can be expressed by the Cardy-Verlinde formula. The later is supposed to be an entropy formula of conformal field theory in any dimension.

physics.gen-ph↗
arXiv2010

The generalized second law of thermodynamics in Horava-Lifshitz cosmology

We investigate the validity of the generalized second law of thermodynamics in a universe governed by Horava-Lifshitz gravity. Under the equilibrium assumption, that is in the late-time cosmological regime, we calculate separately the entropy time-variation for the matter fluid and, using the modified entropy relation, that of the apparent horizon itself. We find that under detailed balance the generalized second law is generally valid for flat and closed geometry and it is conditionally valid for an open universe, while beyond detailed balance it is only conditionally valid for all curvatures. Furthermore, we also follow the effective approach showing that it can lead to misleading results. The non-complete validity of the generalized second law could either provide a suggestion for its different application, or act as an additional problematic feature of Horava-Lifshitz gravity.

hep-th↗
arXiv2010

Plane symmetric solutions in Horava-Lifshitz theory

The purpose of this paper is to find and analyze plane symmetric, static(non static) solutions in Hořava- Lifshitz gravity. We discussed two versions of Horava gravity. First we showed that if the detailed balance principle have considered, there are both static and non-static solutions. We show that in static case there are two family of solvable models which either of them has a well defined EOS, in analogous to the perfect fluid solutions in GR. In non-static case we find a family of solutions. Some physical properties of these solutions was discussed. Secondly we investigated the plane symmetric solutions for a new modified version of Hořavaa gravity \cite{bla}, which has the new terms inserted action in it.

hep-th↗
arXiv2010

Hidden Conformal Symmetry of Extremal Kerr-Bolt Spacetimes

We show that extremal Kerr-Bolt spacetimes have a hidden conformal symmetry. In this regard, we consider the wave equation of a massless scalar field propagating in extremal Kerr-Bolt spacetimes and find in the "near region", the wave equation in extremal limit can be written in terms of the $SL(2,R)$ quadratic Casimir. Moreover, we obtain the microscopic entropy of the extremal Kerr-Bolt spacetimes also we calculate the correlation function of a near-region scalar field and find perfect agreement with the dual 2D CFT.

hep-th↗
arXiv2010

Correspondence between entropy-corrected holographic and Gauss-Bonnet dark energy models

In the present work we investigate the cosmological implications of the entropy-corrected holographic dark energy (ECHDE) density in the Gauss-Bonnet framework. This is motivated from the loop quantum gravity corrections to the entropy-area law. Assuming the two cosmological scenarios are valid simultaneously, we show that there is a correspondence between the ECHDE scenario in flat universe and the phantom dark energy model in the framework of Gauss-Bonnet theory with a potential. This correspondence leads consistently to an accelerating universe.

gr-qc↗
arXiv2010

Holographic dark energy with time depend gravitational constant in the non-flat Ho$\check{r}$ava-Lifshitz cosmology

We study the holographic dark energy on the subject of Ho$\check{r}$ava-Lifshitz gravity with a time dependent gravitational constant (G(t)), in the non-flat space-time. We obtain the differential equation that specify the evolution of the dark energy density parameter based on varying gravitational constant. we find out a relation for the state parameter of the dark energy equation to low redshifts which containing varying $G$ correction.

gr-qc↗
arXiv2010

Hidden Conformal Symmetry of Kerr-Bolt Spacetimes

We extend the recent proposal of hidden conformal symmetry to the four-dimensional spacetimes with rotational parameter and NUT twist. We consider the wave equation of a massless scalar field in background of Kerr-Bolt spacetimes and show in the "near region", the wave equation can be reproduced by the $SL(2,R)_L \times SL(2,R)_R$ Casimir quadratic operators. Moreover, we compute the microscopic entropy of the dual CFT by Cardy formula and find a perfect match to Bekenstein-Hawking entropy of Kerr-Bolt spacetimes. The absorption cross section of a near region scalar field also matches to microscopic absorption cross section of the dual CFT.

hep-th↗
arXiv2010

Correlation functions for Galilean conformal invariant field theory

In this paper we consider non-relativistic-conformal group, then we calculate two point function for the fields that are Galilean conformal-invariant, then we show that the correlation function for Galilean conformal-invariant fields in $d=2$ are different from $d\neq2$. Our result in $d\neq2$ is different with previous results in \cite{3}.

hep-th↗
arXiv2010

Interacting new agegraphic viscous dark energy with varying $G$

We consider the new agegraphic model of dark energy with a varying gravitational constant, $G$, in a non-flat universe. We obtain the equation of state and the deceleration parameters for both interacting and noninteracting new agegraphic dark energy. We also present the equation of motion determining the evolution behavior of the dark energy density with a time variable gravitational constant. Finally, we generalize our study to the case of viscous new agegraphic dark energy in the presence of an interaction term between both dark components.

physics.gen-ph↗
arXiv2010

Thermodynamical description of the interacting new agegraphic dark energy

We describe the thermodynamical interpretation of the interaction between new agegraphic dark energy and dark matter in a non-flat universe. When new agegraphic dark energy and dark matter evolve separately, each of them remains in thermodynamic equilibrium. As soon as an interaction between them is taken into account, their thermodynamical interpretation changes by a stable thermal fluctuation. We obtain a relation between the interaction term of the dark components and this thermal fluctuation.

gr-qc↗