arXiv subjects

M. R. Setare

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

At least 19 recordsLinked to original sources

arXiv2022

Modular Hamiltonian in flat holography in the framework of generalized minimal massive gravity

Recently a general prescription for determining the vacuum modular flow generator and the corresponding modular Hamiltonian in the BMS-invariant field theories (BMSFTs) have provided by Apolo et. al \cite{Apolo}. According to this paper Einstein gravity in asymptotically flat three-dimensional spacetimes is dual to a BMSFT. In the present paper we extend this study to the generalized minimal massive gravity model (GMMG). So we study some aspects of $Flat_3/BMSFT$ holography in the framework of this model. We derive the modular Hamiltonian for single intervals in thermal and non-thermal BMSFTs and show its holographic dual is the gravitational charge associated with isometries that preserve the asymptotic form of the metric. Also using the modular Hamiltonian we derive the first law of entanglement entropy. Our results for GMMG model reduces to the result for Einstein gravity in $2+1$ dimension, when $\mu , m^2 \to \infty $, and $\sigma=-1$. These limiting cases, are a place in parameter space of model, where GMMG model reduces to the Einstein gravity.

hep-th↗

arXiv2022

Holographic Entanglement Entropy in $T\bar{T}$-deformed CFTs

In this work, we study the holographic entanglement entropy of two dimensional $T\bar{T}$-deformed conformal field theory. We compute the correction due to the deformation up to the leading order of the deformation parameter in the framework of New massive gravity, General minimal massive gravity, and Exotic general massive gravity. We also apply Song's prescription to obtain the entanglement entropy for deformed theories. In each cases, we find agreement between the results.

hep-th↗

arXiv2022

The reflected entropy in the GMMG/GCFT flat holography

We extend the reflected entropy to the bipartite state in a two dimensional Galilean conformal field theory ($GCFT_2$) which is dual to the asymptotically flat spacetime described by the generalized minimal massive gravity (GMMG). To this end we consider the Renyi entanglement entropy formula that can be related to the reflected entropy by some manipulations of the replica technique. In a limited case, we find the reflected entropy is twice the minimal entanglement wedge cross section (EWCS) and this is an evidence on the relation between the reflected entropy and the EWCS in the flat holography scenario.

hep-th↗

arXiv2022

Holographic Entanglement negativity in flat space generalized minimal massive gravity

In this paper we study the application of holographic entanglement negativity proposal for bipartite states in the 2d Galilean conformal field theory ($GCFT_2$) dual to bulk asymptotically flat spacetimes in the context of generalized minimal massive gravity (GMMG) model. $GCFT_2$ is considered on the boundary side of the duality and the bulk gravity is described by GMMG that is asymptotically symmetric under the Galilean conformal transformations. In this paper, the replica technique, based on the two-point and the four-point twist correlators, is utilized and the entanglement entropy and the entanglement negativity are obtained in the bipartite configurations of the system in the boundary.

hep-th↗

arXiv2021

Holographic entanglement entropy and modular Hamiltonian in warped CFT in the framework of GMMG model

We study some aspects of a class of non-AdS holography where the 3d bulk gravity is given by Generalized Minimal Massive Gravity (GMMG). We consider the spacelike warped $AdS_3$ ($WAdS_3$) black hole solution of this model where the 2d dual boundary theory is the warped conformal field theory (WFCT). The charge algebra of the isometries in the bulk and the charge algebra of the vacuum symmetries at the boundary are compatible and this is an evidence for the duality conjecture. Further evidence for this duality is the equality of entanglement entropy and modular Hamiltonian on both sides of the duality. So we consider the modular Hamiltonian for the single interval at the boundary in associated to the modular flow generators of the vacuum. We calculate the gravitational charge in associated to the asymptotic Killing vectors that preserve the metric boundary conditions. Assuming the first law of the entanglement entropy to be true, we introduce the matching conditions between the variables in two side of the duality and we find equality of the modular Hamiltonian variations and the gravitational charge variations in two sides of the duality. According to the results of the present paper we can say with more sure that the dual theory of the warped $AdS3$ black hole solution of GMMG is a Warped CFT.

hep-th↗

arXiv2021

Conservation and Integrability in TMG

In this work, following the paper by Romain Ruzziconi and Céline Zwikel \cite{Ruzziconi:2020wrb} we extend the questions of conservation, integrability and renormalization in Bondi gauge and in GR to the theory of Topological Massive Gravity (TMG). We construct the phase space and renormalize the divergences arising within the symplectic structure through a holographic renormalization procedure. We show that the charge expressions are generically finite, conserved and can be made integrable by a field$-$dependent redefinition of the asymptotic symmetry parameters.

hep-th↗

arXiv2021

Vacuum currents in partially compactified Rindler spacetime with an application to cylindrical black holes

The vacuum expectation value of the current density for a charged scalar field is investigated in Rindler spacetime with a part of spatial dimensions compactified to a torus. It is assumed that the field is prepared in the Fulling-Rindler vacuum state. For general values of the phases in the periodicity conditions and the lengths of compact dimensions, the expressions are provided for the Hadamard function and vacuum currents. The current density along compact dimensions is a periodic function of the magnetic flux enclosed by those dimensions and vanishes on the Rindler horizon. The obtained results are compared with the corresponding currents in the Minkowski vacuum. The near-horizon and large-distance asymptotics are discussed for the vacuum currents around cylindrical black holes. In the near-horizon approximation the lengths of compact dimensions are determined by the horizon radius. At large distances from the horizon the geometry is approximated by a locally anti-de Sitter spacetime with toroidally compact dimensions and the lengths of compact dimensions are determined by negative cosmological constant.

hep-th↗

arXiv2021

Kerr/CFT from phase space formalism

Attempts to find black hole microstates using the Hamiltonian phase space approach have been made on the Schwarzschild spacetime. Since the Schwarzschild spacetime is also in the larger family of the Kerr spacetimes, and both are asymptotically flat, the Kerr black hole is a good option for the method development. The Kerr black hole is a spinning one. We perform this analysis on the Kerr spacetime and we obtain promising results using the covariant phase space analysis. Although we have forced ourselves to use the Bondi fall-off conditions, we find the gauge degrees of freedom that could be good candidates for the black hole microstates. The charge algebra on the boundary could be a Virasoro algebra that has a different central term than the Schwarzschild black hole. The two dimensional theory on the black hole boundary is conjectured to be conformally invariant.

gr-qc↗

arXiv2021

Constant-roll inflation from a fermionic field

We study the inflationary period driven by a fermionic field which is non-minimally coupled to gravity in the context of the constant-roll approach. We consider the model for a specific form of coupling and perform the corresponding inflationary analysis. By comparing the result with the Planck observations coming from CMB anisotropies, we find the observational constraints on the parameters space of the model and also the predictions the model. We find that the values of $r$ and $n_{s}$ for $-1.5<β\leq-0.9$ are in good agreement with the observations when $|ξ|=0.1$ and $N=60$.

gr-qc↗

arXiv2021

Hairy Black holes in General Minimal Massive Gravity

In this work, we investigate the near horizon and asymptotic symmetries of static and rotating hairy$-$AdS black hole in the framework of general minimal massive gravity. We obtain energy, angular momentum and entropy of the solutions. Then we show that our results for these quantities are consistent with the first law of black hole thermodynamics. By considering the near horizon geometry of black hole, we find near horizon conserved charges and their algebra. By writing the algebra of conserved charges in terms of Fourier modes we have obtained the conserved charges in terms of zero modes.

hep-th↗

arXiv2021

Phase Transition Between Flat Space Cosmology and Hot Flat Spacetimes in GMMG and EGMG Models

Flat Space Cosmology (FSC) spacetimes are exact solutions of 3D gravity theories. In this work, we study phase transition between FSC spacetimes and Hot Flat Spacetimes (HFS) in general minimal massive gravity and exotic general massive gravity. We show that similar to topological massive gravity the tunneling occurs between two spacetimes by comparing their free energies. We also obtain the corrections to the Bekenstein-Hawking entropy, and its effect on the phase transition is studied.

gr-qc↗

arXiv2021

Holographic Entanglement Entropy in flat limit of the Generalized Minimal Massive Gravity model

Previously we have studied the Generalized Minimal Massive Gravity (GMMG) in asymptotically $AdS_3$ background, and have shown that the theory is free of negative-energy bulk modes. Also we have shown GMMG avoids the aforementioned bulk-boundary unitarity clash. Here instead of $AdS_3$ space we consider asymptotically flat space, and study this model in the flat limit. The dual field theory of GMMG in the flat limit is a $BMS_3$ invariant field theory, dubbed (BMSFT) and we have BMS algebra asymptotically instead of Virasoro algebra. In fact here we present an evidence for this claim. Entanglement entropy of GMMG is calculated in the background in the flat null infinity. Our evidence for mentioned claim is the result for entanglement entropy in filed theory side and in the bulk (in the gravity side). At first using Cardy formula and Rindler transformation, we calculate entanglement entropy of BMSFT in three different cases. Zero temperature on the plane and on the cylinder, and non-zero temperature case. Then we obtain the entanglement entropy in the bulk. Our results in gravity side are exactly in agreement with field theory calculations.

hep-th↗

arXiv2021

Thermalization of horizon through asymptotic symmetry in three-dimensional massive gravity

Recently, black hole symmetries have been studied widely and it has been speculated that this procedure will lead to the deeper understanding of the black hole physics. Spontaneous symmetry breaking of the horizon symmetries is one of the very recent attempt to clarify black hole thermal physics. In this work, we are going to investigate the same in three dimensional massive gravity, including higher order of Riemann tensor. We observe that the idea also works well in this gravitational theory, thereby providing stronger demand of the viability of this idea.

hep-th↗

arXiv2019

Holographically description of Kerr-Bolt Black hole in terms of the warped conformal field theory

Recently it has been speculated that a set of diffeomorphisms exist which act non-trivially on the horizon of some black holes such as Kerr and Kerr-Newman black hole. %\cite{Haco:2018ske,Haco:2019ggi}. Using this symmetry in covariant phase space formalism one can obtain conserved charges as surface integrals on the horizon. Kerr-Bolt spacetime is well-known for its asymptotic topology and has been studied widely in recent years. In this work we are going to study Kerr-Bolt black hole and provide a holographic description of it in term of warped conformal field theory.

hep-th↗

arXiv2019

Kerr-Bolt Black Hole Entropy and Soft Hair

Recently it has been speculated that a set of infinitesimal ${\rm Virasoro_{\,L}}\otimes{\rm Virasoro_{\,R}}$ diffeomorphisms exist which act non-trivially on the horizon of some black holes such as kerr and Kerr-Newman black hole \cite{Haco:2018ske,Haco:2019ggi}. Using this symmetry in covariant phase space formalism one can obtains Virasoro charges as surface integrals on the horizon. Kerr-Bolt spacetime is well-known for its asymptotically topology and has been studied widely in recent years. In this work we are interested to find conserved charge associated to the Virosora symmetry of Kerr-Bolt geometry using covariant phase space formalism. We will show right and left central charge are $c_R=c_L=12 J$ respectively. Our results also show good agreement with Kerr spacetime in the limiting behavior.

hep-th↗

arXiv2019

Radiation properties of an oscillating atom in the presence of external fields

In the first part of the present work, the correction to photon emission rate of an oscillating two-level atom in the presence of electromagnetic quantum vacuum field has been investigated for two different configurations: (i) Atom is trapped in the vicinity of a perfect conductor (ii) Atom is trapped between two perfect conductors. In the second part, the correction to the decay rate of an initially excited oscillating two-level atom due to the presence of a perfect conducting surface is found.

quant-ph↗

arXiv2019

de Sitter field equations from quadratic curvature gravity: A group theoretical approach

In this paper, the linearized field equations related to the quadratic curvature gravity theory have been obtained in the four-dimensional de Sitter (dS) space-time. The massless spin-2 field equations have been written in terms of the Casimir operators of dS group making use of the ambient space notations. By imposing some simple constraints, arisen from group theoretical interpretation of the field equations, a new four-dimensional Gauss-Bonnet (GB)-like action has been introduced with the related field equations transforming according to the unitary irreducible representations (UIR's) of dS group. Since, the field equations transform according to the UIR's of dS group, the GB-like action, we just obtained, is expected to be a successful model of modified gravity. For more clarifying, the gauge invariant field equations have been solved in terms of a gauge-fixing parameter ${\cal{C}}$. It has been shown that the solution can be written as the multiplication of a symmetric rank-2 polarization tensor and a massless minimally coupled scalar field on dS space. The Gupta-Bleuler quantization method has been utilized and the covariant two-point function has been calculated in terms of the massless minimally coupled scalar two-point function, using the ambient space notations. It has been written in terms of dS intrinsic coordinates from the ambient space counterpart. The two-point functions are dS invariant and free of any theoretical problems. It means that the proposed model is a successful model of modified gravity and it can produce significant results in the contexts of classical theory of gravity and quantum gravity toy models.

gr-qc↗

arXiv2019

Dilaton black holes with power law electrodynamics

In this article, the new black hole solutions to the Einstein-power-Maxwell-dilaton gravity theory have been investigated in a four-dimensional space-time. The coupled scalar, electromagnetic and gravitational field equations have been solved in a static and spherically symmetric geometry. It has been shown that dilatonic potential, as the solution to the scalar field equation, can be written in the form of a generalized Liouville potential. Also, three classes of novel charged dilaton black hole solutions, in the presence of power law nonlinear electrodynamics, have been constructed out which are asymptotically non-flat and non-AdS. The conserved and thermodynamic quantities have been calculated from geometrical and thermodynamical approaches, separately. Since the results of these two alternative approaches are identical one can argue that the first law of black hole thermodynamics is valid for all of the new black hole solutions. The thermodynamic stability or phase transition of the black holes have been studied, making use of the canonical ensemble method. The points of type-1 and type-2 phase transitions as well as the ranges at which the black holes are stable have been indicated by considering the heat capacity of the new black hole solutions. The global stability of the black holes have been studied through the grand canonical ensemble method. Regarding the Gibbs free energy of the black holes, the points of Hawking-Page phase transition and ranges of the horizon radii at which the black holes are globally stable have been determined.

gr-qc↗