arXiv subjects

M. Kord Zangeneh

Publications and source records attributed to M. Kord Zangeneh.

At least 19 recordsLinked to original sources

arXiv2026

Quasi-normal modes as probes of black hole reentrant phase transitions

We investigate the interplay between thermodynamic phase transitions and the dynamical behavior of quasi-normal modes (QNMs) in weakly nonlinear charged anti-de Sitter black holes. In a non-extended phase space, we identify a reentrant large-small-large(intermediate) phase transition for these black holes. Employing the shooting method to solve the Klein-Gordon equation for a massless scalar field, we compute QNM frequencies across these phases, revealing distinct behaviors in different phases. Specifically, to our knowledge, this is the first report of utilizing QNMs as dynamical probes of thermodynamic phases during reentrant phase transitions including zeroth and first-order transitions. These findings establish QNMs as a powerful dynamical probe for thermodynamic phase transitions, providing new insights into the thermodynamic and dynamical properties of nonlinear charged black holes as well.

gr-qc↗

arXiv2020

Topological Born-Infeld charged black holes in Einsteinian cubic gravity

In this paper, we study four-dimensional topological black hole solutions of Einsteinian cubic gravity in the presence of nonlinear Born-Infeld electrodynamics and a bare cosmological constant. First, we obtain the field equations which govern our solutions. Employing Abbott-Deser-Tekin and Gauss formulas, we present the expressions of conserved quantities, namely total mass and total charge of our topological black solutions. We disclose the conditions under which the model is unitary and perturbatively free of ghosts with asymptotically (A)dS and flat solutions. We find that, for vanishing bare cosmological constant, the model is unitary just for asymptotically flat solutions, which only allow horizons with spherical topology. We compute the temperature for these solutions and show that it always has a maximum value, which decreases as the values of charge, nonlinear coupling or cubic coupling grows. Next, we calculate the entropy and electric potential. We show that the first law of thermodynamics is satisfied for spherical asymptotically flat solutions. Finally, we peruse the effects of model parameters on thermal stability of these solutions in both canonical and grand canonical ensembles.

hep-th↗

arXiv2020

Generalized entropies and corresponding holographic dark energy models

Using Tsallis statistics and its relation with Boltzmann entropy, the Tsallis entropy content of black holes is achieved, a result in full agreement with a recent study (Phys. Lett. B 794, 24 (2019)). In addition, employing Kaniadakis statistics and its relation with that of Tsallis, the Kaniadakis entropy of black holes is obtained. The Sharma-Mittal and Rényi entropy contents of black holes are also addressed by employing their relations with Tsallis entropy. Thereinafter, relying on the holographic dark energy hypothesis and the obtained entropies, two new holographic dark energy models are introduced and their implications on the dynamics of a flat FRW universe are studied when there is also a pressureless fluid in background. In our setup, the apparent horizon is considered as the IR cutoff, and there is not any mutual interaction between the cosmic fluids. The results indicate that the obtained cosmological models have $i$) notable powers to describe the cosmic evolution from the matter-dominated era to the current accelerating universe, and $ii$) suitable predictions for the universe age.

gr-qc↗

arXiv2020

Thermodynamics and reentrant phase transition for logarithmic nonlinear charged black holes in massive gravity

We investigate a new class of $(n+1)$-dimensional topological black hole solutions in the context of massive gravity and in the presence of logarithmic nonlinear electrodynamics. Exploring higher dimensional solutions in massive gravity coupled to nonlinear electrodynamics is motivated by holographic hypothesis as well as string theory. We first construct exact solutions of the field equations and then explore the behavior of the metric functions for different values of the model parameters. We observe that our black holes admit the multi-horizons caused by a quantum effect called anti-evaporation. Next, by calculating the conserved and thermodynamic quantities, we obtain a generalized Smarr formula. We find that the first law of black holes thermodynamics is satisfied on the black hole horizon. We study thermal stability of the obtained solutions in both canonical and grand canonical ensembles. We reveal that depending on the model parameters, our solutions exhibit a rich variety of phase structures. Finally, we explore, for the first time without extending thermodynamics phase space, the critical behavior and reentrant phase transition for black hole solutions in massive gravity theory. We realize that there is a zeroth order phase transition for a specified range of charge value and the system experiences a large/small/large reentrant phase transition due to the presence of nonlinear electrodynamics.

gr-qc↗

arXiv2019

A note on cosmological features of modified Newtonian potentials

Considering some modified Newtonian potentials and the Hubble law in writing the total energy of a test mass located at the edge of a flat Friedmann-Robertson-Walker universe, we obtain several modified Friedmann equations. Interestingly enough, our study shows that the employed potentials, while some of them have some successes in modelling the spiral galaxies rotation curves, may also address an accelerated universe. This fact indicates that dark energy and dark matter may have some common origins and aspects.

physics.gen-ph↗

arXiv2018

One-dimensional backreacting holographic superconductors with exponential nonlinear electrodynamics

In this paper, we investigate the effects of nonlinear exponential electrodynamics as well as backreaction on the properties of one-dimensional $s$-wave holographic superconductors. We continue our study both analytically and numerically. In analytical study, we employ the Sturm-Liouville method while in numerical approach we perform the shooting method. We obtain a relation between the critical temperature and chemical potential analytically. Our results show a good agreement between analytical and numerical methods. We observe that the increase in the strength of both nonlinearity and backreaction parameters causes the formation of condensation in the black hole background harder and critical temperature lower. These results are consistent with those obtained for two dimensional $s$-wave holographic superconductors.

hep-th↗

arXiv2017

Optical properties of Born-Infeld-dilaton-Lifshitz holographic superconductors

In this paper, we first study the Lifshitz-dilaton holographic superconductors with nonlinear Born-Infeld (BI) gauge field and obtain the critical temperature of the system for different values of Lifshitz dynamical exponent, $z$, and nonlinear parameter $b$. We find that for fixed value of $b$, the critical temperature decreases with increasing $z$. This indicates that the increase of anisotropy between space and time prevents the phase transition. Also, for fixed value of $z$, the critical temperature decrease with increasing $b$. Then, we investigate the optical properties of ($2+1$) and ($3+1$)-dimensional BI-Lifshitz holographic superconductors in the the presence of dilaton field. We explore the refractive index of the system. For $z=1$ and $(2+1)$-dimensional holographic superconductor, we observe negative real part for permittivity $\textrm{Re}[ε]$ as frequency $ω$ decreases. Thus, in low frequency region our superconductor exhibit metamaterial property. This behaviour is independent of the nonlinear parameter and can be seen for either linear ($b=0$) and nonlinear ($b\neq 0$) electrodynamics. Interestingly, for ($3+1$)-dimensional Lifshitz-dilaton holographic superconductors, we observe metamaterial behavior neither in the presence of linear nor nonlinear electrodynamics.

hep-th↗

arXiv2017

Microscopic Origin of Black Hole Reentrant Phase Transitions

Understanding the microscopic behavior of the black holes ingredients has been one of the important challenges in black holes physics during the past decades. In order to shed some light on the microscopic structure of black holes, in this paper, we explore a recently observed phenomenon for black holes namely reentrant phase transition, by employing the Ruppeiner geometry. Interestingly enough, we observe two properties for the phase behaviour of small black holes that leads to reentrant phase transition. They are correlated and they are of the interaction type. For the range of pressure in which the system underlies reentrant phase transition, it transits from large black holes phase to small one which possesses higher correlation than the other ranges of pressures. On the other hand, the type of interaction between small black holes near large/small transition line, differs for usual and reentrant phase transitions. Indeed, for usual case, the dominant interaction is repulsive whereas for reentrant case we encounter with an attractive interaction. We show that in reentrant phase transition case, the small black holes behave like a Bosonic gas whereas in the usual phase transition case, they behave like a quantum anyon gas.

hep-th↗

arXiv2017

Holographic conductivity in the massive gravity with power-law Maxwell field

We obtain a new class of topological black hole solutions in $(n+1)$-dimensional massive gravity in the presence of the power-Maxwell electrodynamics. We calculate the conserved and thermodynamic quantities of the system and show that the first law of thermodynamics is satisfied on the horizon. Then, we investigate the holographic conductivity for the four and five dimensional black brane solutions. For completeness, we study the holographic conductivity for both massless ($m=0$) and massive ($m \neq 0$) gravities with power-Maxwell field. The massless gravity enjoys translational symmetry whereas the massive gravity violates it. For massless gravity, we observe that the real part of conductivity, $\mathrm{Re}[σ]$, decreases as charge $q$ increases when frequency $ω$ tends to zero, while the imaginary part of conductivity, $\mathrm{Im}[σ]$, diverges as $ω\rightarrow 0$. For the massive gravity, we find that $\mathrm{Im}[σ]$ is zero at $ω=0$ and becomes larger as $q$\ increases (temperature decreases), which is in contrast to the massless gravity. Interestingly, we observe that in contrast to the massless case, $\mathrm{Re}[σ]$ has a maximum value at $ω=0$ (known as the Drude peak) for $p=\left( n+1\right) /4$ (conformally invariant electrodynamics) where $p$ is the power parameter of the power-law Maxwell field and this maximum increases with increasing $q$. Finally, we show that for high frequencies, the real part of the holographic conductivity have the power law behavior in terms of frequency, $ω^{a}$ where $a \propto (n+1-4p)$. Some similar behaviors for high frequencies in possible dual CFT systems have been reported in experimental observations.

hep-th↗

arXiv2017

Charged scalar quasi-normal modes for linearly charged dilaton-Lifshitz solutions

Most available studies of quasi-normal modes for Lifshitz black solutions are limited to the neutral scalar perturbations. In this paper, we investigate the wave dynamics of massive charged scalar perturbation in the background of $(3+1)$-dimensional charged dilaton Lifshitz black branes/holes. We disclose the dependence of the quasi-normal modes on the model parameters, such as the Lifshitz exponent $z$, the mass and charge of the scalar perturbation field and the charge of the Lifshitz configuration. In contrast with neutral perturbations, we observe the possibility to destroy the original Lifshitz background near the extreme value of charge where the temperature is low. We find out that when the Lifshitz exponent deviates more from unity, it is more difficult to break the stability of the configuration. We also study the behavior of the real part of the quasi-normal frequencies. Unlike the neutral scalar perturbation around uncharged black branes where an overdamping was observed to start at $z=2$ and independent of the value of scalar mass, our observation discloses that the overdamping starting point is no longer at $z=2$ and depends on the mass of scalar field for charged Lifshitz black branes. For charged scalar perturbations, fixing $m_s$, the asymptotic value of $ω_R$ for high $z$ is more away from zero when the charge of scalar perturbation $q_s$ increases. There does not appear the overdamping.

hep-th↗

arXiv2016

Thermodynamics, phase transitions and Ruppeiner geometry for Einstein-dilaton Lifshitz black holes in the presence of Maxwell and Born-Infeld electrodynamics

In this paper, we first obtain the ($n+1$)-dimensional dilaton-Lifshitz black hole (BH) solutions in the presence of Born-Infeld (BI) electrodynamics. We find that there are two different solutions for $z=n+1$ and $z\neq n+1$ cases ($z$ is dynamical critical exponent). We show that the thermodynamics first law is satisfied for both cases. Then, we turn to study different phase transitions (PTs) for our BHs. We start with study of Hawking-Page PT for both linearly and BI charged BHs. After that, we discuss the PTs inside the BHs. We present the improved Davies quantities and prove that the PT points shown by them coincide with Ruppeiner ones. We show that the zero temperature PTs are transitions on radiance properties of BHs by using Landau-Lifshitz theory. Next, we turn to study Ruppeiner geometry of linearly and BI charged BHs. For linearly charged case, we show that there are no PT at finite temperature for the case $z\geq 2$. For $z<2$, it is found that the number of finite temperature PT points depends on the value of BH charge and is not more than two. When we have two finite temperature PT points, there are no thermally stable BH between these two points and we have discontinues small/large BH PTs. As expected, for small BHs, we observe finite magnitude for Ruppeiner invariant which shows the finite correlation between possible BH molecules while for large BHs, the correlation is very small. Finally, we study the Ruppeiner geometry and thermal stability of BI charged Lifshtiz BHs for different values of $z$. We observe that small BHs are thermally unstable in some situations. Also, the behavior of correlation between possible BH molecules for large BHs is the same as linearly charged case. In both linearly and BI charged cases, for some choices of parameters, the BH systems behave like a Van der Waals gas near transition point.

hep-th↗

arXiv2016

Holographic Conductivity for Logarithmic Charged Dilaton-Lifshitz Solutions

We disclose the effects of the logarithmic nonlinear electrodynamics on the holographic conductivity of Lifshitz dilaton black holes/branes. We analyze thermodynamics of these solutions as a necessary requirement for applying gauge/gravity duality, by calculating conserved and thermodynamic quantities such as the temperature, entropy, electric potential and mass of the black holes/branes. We calculate the holographic conductivity for a $(2+1)$-dimensional brane boundary and study its behavior in terms of the frequency per temperature. Interestingly enough, we find out that, in contrast to the Lifshitz-Maxwell-dilaton black branes which has conductivity for all $z$, here in the presence of nonlinear gauge field, the holographic conductivity do exist provided $z\leq3$ and vanishes for $z>3$. It is shown that independent of the nonlinear parameter $β$, the real part of the conductivity is the same for a specific value of frequency per temperature in both AdS and Lifshitz cases. Besides, the behavior of real part of conductivity for large frequencies has a positive slope with respect to large frequencies for a system with Lifshitz symmetry whereas it tends to a constant for a system with AdS symmetry. This behavior may be interpreted as existence of an additional charge carrier rather than the AdS case, and is due to the presence of the scalar dilaton field in model. Similar behavior for optical conductivity of single-layer graphene induced by mild oxygen plasma exposure has been reported.

hep-th↗

arXiv2016

Thermodynamics of charged rotating dilaton black branes coupled to logarithmic nonlinear electrodynamics

We construct a new class of charged rotating black brane solutions in the presence of logarithmic nonlinear electrodynamics with complete set of the rotation parameters in arbitrary dimensions. The topology of the horizon of these rotating black branes are flat, while, due to the presence of the dilaton field the asymptotic behaviour of them are neither flat nor (anti)-de Sitter [(A)dS]. We investigate the physical properties of the solutions. The mass and angular momentum of the spacetime are obtained by using the counterterm method inspired by AdS/CFT correspondence. We derive temperature, electric potential and entropy associated with the horizon and check the validity of the first law of thermodynamics on the black brane horizon. We study thermal stability of the solutions in both canonical and grand canonical ensemble and disclose the effects of the rotation parameter, nonlinearity of electrodynamics and dilaton field on the thermal stability conditions. We find the solutions are thermally stable for $α<1$, while for $α>1$ the solutions may encounter an unstable phase where $α$ is dilaton-electromagnetic coupling constant.

gr-qc↗

arXiv2016

Thermodynamics and gauge/gravity duality for Lifshitz black holes in the presence of exponential electrodynamics

In this paper, we construct a new class of topological black hole Lifshitz solutions in the presence of nonlinear exponential electrodynamics for Einstein-dilaton gravity. We show that the reality of Lifshitz supporting Maxwell matter fields exclude the negative horizon curvature solutions except for the asymptotic AdS case. Calculating the conserved and thermodynamical quantities, we obtain a Smarr type formula for the mass and confirm that thermodynamics first law is satisfied on the black hole horizon. Afterward, we study the thermal stability of our solutions and figure out the effects of different parameters on the stability of solutions under thermal perturbations. Next, we apply the gauge/gravity duality in order to calculate the ratio of shear viscosity to entropy for a three-dimensional hydrodynamic system by using the pole method. Furthermore, we study the behavior of holographic conductivity for two-dimensional systems such as graphene. We consider linear Maxwell and nonlinear exponential electrodynamics separately and disclose the effect of nonlinearity on holographic conductivity. We indicate that holographic conductivity vanishes for $z>3$ in the case of nonlinear electrodynamics while it does not in the linear Maxwell case. Finally, we solve perturbative additional field equations numerically and plot the behaviors of real and imaginary parts of conductivity for asymptotic AdS and Lifshitz cases. We present experimental results match with our numerical ones.

hep-th↗

arXiv2016

Comment on "Insight into the Microscopic Structure of an AdS Black Hole from a Thermodynamical Phase Transition"

Thermodynamic geometry analysis of interesting Letter [Phys. Rev. Lett. 115, 111302 (2015)] for charged AdS black holes, which is based on studying the Ruppeiner invariant behavior is not correct and the authors made a mistake in calculating this quantity. In the present Letter, we address the correct Ruppeiner scalar curvature and reveal the correct possible microscopic properties of 4-dimensional charged AdS black holes arise from it. Some of these properties have not been discussed in pointed out Letter.

hep-th↗

arXiv2015

Thermodynamics of topological black holes in Brans-Dicke gravity with a power-law Maxwell field

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 conditions under which we have black holes. Interestingly enough, we show that there is a cosmological horizon in the presence of a negative cosmological constant. Finally, we calculate the temperature and charge and then by calculating the Euclidean action, we obtain the mass, the entropy and the electromagnetic potential energy. We find that the entropy does not respect the area law, and also the conserved and thermodynamic quantities are invariant under conformal transformation. Using these thermodynamic and conserved quantities, we show that the first law of black hole thermodynamics is satisfied on the horizon.

gr-qc↗

arXiv2015

Thermodynamics of Gauss-Bonnet-Dilaton Lifshitz Black Branes

We explore an effective supergravity action in the presence of a massless gauge field which contains the Gauss-Bonnet term as well as a dilaton field. We construct a new class of black brane solutions of this theory with the Lifshitz asymptotic by fixing the parameters of the model such that the asymptotic Lifshitz behavior can be supported. Then we construct the well-defined finite action through the use of the counterterm method. We also obtain two independent constants along the radial coordinate by combining the equations of motion. Calculations of these two constants at infinity through the use of the large-$r$ behavior of the metric functions show that our solution respects the no-hair theorem. Furthermore, we combine these two constants in order to get a constant $C$ which is proportional to the energy of the black brane. We calculate this constant at the horizon in terms of the temperature and entropy, and at large-$r$ in terms of the geometrical mass. By calculating the value of the energy density through the use of the counterterm method, we obtain the relation between the energy density, the temperature, and the entropy. This relation is the generalization of the well-known Smarr formula for AdS black holes. Finally, we study the thermal stability of our black brane solution and show that it is stable under thermal perturbations.

hep-th↗

arXiv2015

Thermodynamics of topological nonlinear charged Lifshitz black holes

In this paper, we construct a new class of analytic topological Lifshitz black holes with constant curvature horizon in the presence of power-law Maxwell field in four and higher dimensions. We find that in order to obtain these exact Lifshitz solutions, we need a dilaton and at least three electromagnetic fields. Interestingly enough, we find that the reality of the charge of the electromagnetic field which is needed for having solutions with curved horizon rules out black holes with hyperbolic horizon. Next, we study the thermodynamics of these nonlinear charged Lifshitz black holes with spherical and flat horizons by calculating all the conserved and thermodynamic quantities of the solutions. Furthermore, we obtain a generalized Smarr formula and show that the first law of thermodynamics is satisfied. We also perform a stability analysis in both canonical and grand-canonical ensemble. We find that the solutions are thermally stable in a proper ranges of the metric parameters. Finally, we comment on the dynamical stability of the obtained solutions under perturbations in four dimensions.

gr-qc↗