arXiv subjects

Kh. Jafarzade

Publications and source records attributed to Kh. Jafarzade.

13 recordsLinked to original sources

arXiv2024

Thermodynamics and Optical Properties of Phantom AdS Black Holes in Massive Gravity

Motivated by high interest in Lorentz invariant massive gravity models known as dRGT massive gravity, we present an exact phantom black hole solution in this theory of gravity and discuss the thermodynamic structure of the black hole in the canonical ensemble. Calculating the conserved and thermodynamic quantities, we check the validity of the first law of thermodynamics and the Smarr relation in the extended phase space. In addition, we investigate both the local and global stability of these black holes and show how massive parameters affect the regions of stability. We extend our study to investigate the optical features of the black holes such as the shadow geometrical shape, energy emission rate, and deflection angle. Also, we discuss how these optical quantities are affected by massive coefficients. Finally, we consider a massive scalar perturbation minimally coupled to the background geometry of the black hole and examine the quasinormal modes (QNMs) by employing the WKB approximation.

gr-qc↗

arXiv2023

A Comprehensive Review of Geometrical Thermodynamics: From Fluctuations to Black Holes

This paper presents a comprehensive review of geometrical thermodynamics, which employs geometric concepts to study the thermodynamic properties of physical systems. The review covers key topics such as thermodynamic fluctuation theory, proposed thermodynamic metrics in various coordinate systems, and thermodynamic curvature. Additionally, the paper discusses the geometrical approach to black hole thermodynamics and provides an overview of recent research in this field.

gr-qc↗

arXiv2023

Rotating Lifshitz-like black holes in F(R) gravity

Regarding a particular class of pure $F(R)$ gravity in three dimensions, we obtain an analytical rotating Lifshitz-like black hole solution. We first investigate some geometrical properties of the obtained solution that reduces to a charged rotating BTZ black hole in a special limit. Then, we study the optical features of such a black hole like the photon orbit and the energy emission rate and discuss how electric charge, angular momentum, and exponents affect them. In order to have an acceptable optical behavior, we should apply some constraints on the exponents. We continue our investigation with the study of the thermodynamic behavior of the solutions in the extended phase space and examine the validity of the first law of thermodynamics besides local thermal stability through using of heat capacity. Evaluating the existence of van der Waals-like phase transition, we obtain critical quantities and show how they change under the variation of black hole parameters. Finally, we construct a holographic heat engine of such a black hole and obtain its efficiency in a cycle. By comparing the obtained efficiency with the Carnot one, we examine the second law of thermodynamics.

hep-th↗

arXiv2023

Black holes in dRGT massive gravity with the signature of EHT observations of M87*

The recent Event Horizon Telescope (EHT) observations of the M87* have led to a surge of interest in studying the shadow of black holes. Besides, investigation of time evolution and lifetime of black holes helps us to veto/restrict some theoretical models in gravitating systems. Motivated by such exciting properties, we study optical features of black holes, such as the shadow geometrical shape and the energy emission rate in modified gravity. We consider a charged AdS black hole in dRGT massive gravity and look for criteria to restrict the free parameters of the theory. The main goal of this paper is to compare the shadow of the mentioned black hole in a rotating case with the EHT data to obtain the allowed regions of the model parameters. Therefore, we employ the Newman-Janis algorithm to build the rotating counterpart of static solution in dRGT massive gravity. We also calculate the energy emission rate for the rotating case and discuss how the rotation factor and other parameters affect the emission of particles around the black holes.

gr-qc↗

arXiv2022

Gauss-Bonnet black holes in a special anisotropic scaling spacetime

Inspired by the Lifshitz gravity as a theory with anisotropic scaling behavior, we suggest a new $(n+1)-$dimensional metric in which the time and spatial coordinates scale anisotropically as $(t,r,θ_{i})\,\to (λ^{z}t,λ^{-1}r,λ^{x_i}\,θ_{i})$. Due to the anisotropic scaling dimension of the spatial coordinates, this spacetime does not support the full Schrödinger symmetry group. We look for the analytical solution of Gauss-Bonnet gravity in the context of the mentioned geometry. We show that Gauss-Bonnet gravity admits an analytical solution provided that the constants of the theory are properly adjusted. We obtain an exact vacuum solution, independent of the value of the dynamical exponent $z$, which is a black hole solution for the pseudo-hyperbolic horizon structure and a naked singularity for the pseudo-spherical boundary. We also obtain another exact solution of Gauss-Bonnet gravity under certain conditions. After investigating some geometrical properties of the obtained solutions, we consider the thermodynamic properties of these topological black holes and study the stability of the obtained solutions for each geometrical structure.

gr-qc↗

arXiv2022

Thermal Stability, P-V Criticality and Heat Engine of Charged Rotating Accelerating Black Holes

In this paper, we study thermodynamic features of the charged rotating accelerating black holes in anti-de Sitter spacetime. First, we consider these black holes as the thermodynamic systems and analyze thermal stability/instability through the use of heat capacity in the canonical ensemble. We also investigate the effects of angular momentum, electric charge and string tension on the thermodynamic quantities and stability of the system. Considering the known relation between pressure and the cosmological constant, we extract the critical quantities and discuss how the mentioned parameters affect them. Then, we construct a heat engine by taking into account this black hole as the working substance, and obtain the heat engine efficiency by considering a rectangle heat cycle in the $P-V$ plane. We examine the effects of black hole parameters on the efficiency and analyze their effective roles. Finally, by comparing the engine efficiency with Carnot efficiency, we investigate conditions in order to have a consistent thermodynamic second law.

hep-th↗

arXiv2021

Geometrical thermodynamics and P-V criticality of charged accelerating AdS black holes

The unusual asymptotic structure of the accelerating black holes led to ambiguity in their geometric characteristics and thermodynamic behavior. Motivated by the interesting properties of such black holes and the significant role of electric charge and string tension on their structure, we study the thermodynamic behavior of these black holes by two methods and examine the changes of free parameters on the thermal behavior of the black holes. First, we investigate phase transition and thermal stability of the system through the use of heat capacity in the non-extended phase space. We examine the effects of electric charge, string tension and the cosmological constant on the phase transition and stability of the system. We also find that to have a phase transition, we have to apply some constraints on the free parameters. Then, we employ the geometrical thermodynamic (GT) method to study phase transition and compare the obtained results with those of the heat capacity. Next, we work in the extended phase space by considering the cosmological constant as a dynamical pressure and evaluate the existence of van der Waals like phase transition. We obtain critical quantities and study the effective role of electric charge and string tension on these quantities. Finally, we make use of the GT method in the extended phase space and find that the results of the GT method, heat capacity and $P-V$ diagram lead to a consistent conclusion.

hep-th↗

arXiv2021

Critical behavior of charged AdS black holes surrounded by quintessence via an alternative phase space

Considering the variable cosmological constant in the extended phase space has a significant background in the black hole physics. It was shown that the thermodynamic behavior of charged AdS black hole surrounded by the quintessence in the extended phase space is similar to the van der Waals fluid. In this paper, we indicate that such a black hole admits the same criticality and van der Waals like behavior in the non-extended phase space. In other words, we keep the cosmological constant as a fixed parameter, and instead, we consider the normalization factor as a thermodynamic variable. We show that there is a first-order small/large black hole phase transition which is analogous to the liquid/gas phase transition in fluids. We introduce a new picture of the equation of state and then we calculate the corresponding critical quantities. Moreover, we obtain the critical exponents and show that they are the same values as the van der Waals system. Finally, we study the photon sphere and the shadow observed by a distant observer and investigate how the shadow radius may be affected by the variation of black hole parameters. We also investigate the relations between shadow radius and phase transitions and calculate the critical shadow radius where the black hole undergoes a second-order phase transition.

hep-th↗

arXiv2020

Charged 4D Einstein-Gauss-Bonnet-AdS Black Holes: Shadow, Energy Emission, Deflection Angle and Heat Engine

Recently, there has been a surge of interest in the 4D Einstein-Gauss-Bonnet (4D EGB) gravity theory which bypasses the Lovelock theorem and avoids Ostrogradsky's instability. Such a novel theory has nontrivial dynamics and presents several predictions for cosmology and black hole physics. Motivated by recent astrophysical observations and the importance of anti-de Sitter spacetime, we investigate shadow geometrical shapes and deflection angle of light from the charged AdS black holes in 4D EGB gravity theory. We explore the shadow behaviors and photon sphere around such black holes, and inspect the effect of different parameters on them. Then, we present a study regarding the energy emission rate of such black holes and analyze the significant role of the Gauss-Bonnet (GB) coupling constant in the radiation process. Then, we perform a discussion of holographic heat engines of charged 4D EGB-AdS black holes by obtaining the efficiency of a rectangular engine cycle. Finally, by comparing heat engine efficiency with the Carnot efficiency, we indicate that the ratio $\frac{η}{η_{c}}$ is always less than one which is consistent with the thermodynamic second law.

hep-th↗

arXiv2018

Effects of dark energy on $P-V$ criticality and efficiency of charged Rotational black hole

In this paper, we study $P-V$ criticality of Kerr-Newman $AdS$ black hole with a quintessence field. We calculate critical quantities and show that for the equation state parameter $ω= -\frac{1}{3}$, the obtained universal ratio ($\frac{P_{c}\upsilon_{c}}{T_{c}}$) is quite same as Kerr-Newman $AdS$ black hole without dark energy parameter. We investigate the influence of quintessence field $α$, equation state parameter $ω$ and angular momentum $J$ on the efficiency $η$. We find that $η$ is increased by increasing $J$ and $α$ and decreasing charge $Q$ of black hole. We show when $ω$ increases from $-1$ to $-\frac{1}{3}$ the efficiency decreases. Also we study ratio $\fracη{η_{C}}$ (which $η_{C}$ is the Carnot efficiency) and see that the second law of the thermodynamics is satisfied by special values of $J$ and $α$ and holds for any value of $Q$. We notice that in this case by increasing $ω$ from $-1$ to $-\frac{1}{3}$ the range of $J$ and $α$ increases.

hep-th↗

arXiv2017

The Thermodynamic Efficiency in Static and Dynamic Black Holes

We note that, in extended phase space the cosmological constant is a thermodynamic variable. In this paper, this cosmological constant lead us to consider a black hole as a heat engine. So, here we take advantage from holographic heat engine and study two kind of different black holes. We first investigate a static black hole (Dyonic BH) and consider the necessary condition to have high efficiency. Also we continue our investigation for dynamic black hole (rotating charged black hole) and study the effect of rotating parameter on the thermodynamic efficiency of holographic heat engine. We show that the rotating parameter has a more effective role than electric charge in thermodynamic efficiency.

hep-th↗

arXiv2017

Phase Transition of charged Rotational Black Hole and Quintessence

In this paper, we calculate thermodynamical quantity of Kerr-Newman-AdS black hole solution in quintessence matter. Then, we show that how the rotation and cosmological parameters effect to the thermodynamics properties of black hole. Also, we investigate both types of phase transition for different values of $ω$ parameter in extended phase space. We notice that type one of phase transition occurs for $P<0.42$ and $a<0.5$. And also we see that the phase transition point shifts to higher entropy when pressure $P$, rotation parameter $a$ and $α$ increase. Also, we find that by changing parameter $ω$ from -1 to $-\frac{1}{3}$, the critical point shifts to higher entropy. Then we study type two of phase transition and show critical points increase by increasing parameter $α$. Also, we show that the critical point shifts to higher entropy when $α$, $ω$ and rotation parameter $a$ decrease. Finally, we find that by decreasing pressure the first critical point shifts to lower entropy and second critical point shifts to higher entropy.

hep-th↗

arXiv2017

The phase transition and holographic in modified Horava -Lifshitz black hole

In this paper, we take cosmological constant as a thermodynamical pressure and it's conjugate quantity as a thermodynamical volume. This expression help us to investigate the phase transition and holographic heat engine. So, in order to have Van der Waals fluid behaviour in Horava -Lifshitz (HL) black hole, we modified the solution of such black hole with some cosmology ansatz. Also from holographic heat engine, we obtain Carnot efficiency for the HL black hole. The phase transition of the system lead us to investigate the stability condition for the corresponding black hole. In that case, we show that the stability exist only in special region of black hole.

hep-th↗