**T (+98) 23 352 20220**

Email: international@du.ac.ir

Damghan University

University Blvd, Damghan, IR

Behnam Pourhassan

Assistant Professor of Fundamental Particle Physics

- Particle Physics
- Classical Mechanics
- Research method
- Mathematical Physics
- Elementary Particle Physics
- Classical Mechanics
- String Theory
- Thermodynamics
- Electromagnetism
- Differential Equations
- Statistical Mechanics
- Analytical Mechanics
- Quantum Mechanics
- Research title

DOI: 10.1016/j.aop.2018.10.011

In this paper, we consider the rotating charged Gödel black hole and study the effect of the higher order corrections of the entropy on the thermodynamics and statistics quantities of the Kerr–Newman–Gödel black hole. The leading order correction is logarithmic while higher-order terms are proportional to the inverse of the area of the black hole. We obtain modified thermodynamics and statistics and find that correction terms are important in the stability of the black hole. © 2018 Elsevier Inc.

AUTHOR KEYWORDS: Black hole; Statistics; Thermal fluctuations; Thermodynamics

PUBLISHER: Academic Press Inc.

DOI: 10.1142/S0218271818501183

It is known that almost all approaches to quantum gravity produce a logarithmic correction term to the entropy of a black hole, but the exact coefficient of such a term varies between the different approach to quantum gravity. Such logarithmic terms can also occur due to thermal fluctuations in both analogous and real black holes so that we will analyze the effects of logarithmic corrections term with variable coefficient on properties of analogous black hole. As these properties can be experimentally tested, they can be used to obtain the correct coefficient for such terms for an analogous black hole. We will argue that as even the real black holes can be considered as thermodynamical objects in Jacobson formalism, so such analogous black holes can be used to obtain the correct coefficient for the real black holes, and this in turn can be used to select the correct approach to quantum gravity. In that case, we use an adaptive model of graphene, which is still far from real graphene, to investigate some thermodynamics quantities of BTZ black hole. © 2018 World Scientific Publishing Company.

AUTHOR KEYWORDS: Black hole; quantum gravity; thermal fluctuation

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1140/epjc/s10052-018-6172-7

We analyze certain aspects of BTZ black holes in massive theory of gravity. The black hole solution is obtained by using the Vainshtein and dRGT mechanism, which is asymptotically AdS with an electric charge. We study the Hawking radiation using the tunneling formalism as well as analyze the black hole chemistry for such system. Subsequently, we use the thermodynamic pressure-volume diagram to explore the efficiency of the Carnot heat engine for this system. Some of the important features arising from our solution include the non-existence of quantum effects, critical Van der Walls behaviour, thermal fluctuations and instabilities. Moreover, our solution violates the Reverse Isoperimetric Inequality and, thus, the black hole is super-entropic, perhaps which turns out to be the most interesting characteristics of the BTZ black hole in massive gravity. © 2018, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1088/1475-7516/2018/06/038

In this paper, we will analyze a time dependent geometry in a massive theory of gravity. This will be done by analyzing Vaidya spacetime in such a massive theory of gravity. As gravitational collapse is a time dependent system, we will analyze it using the Vaidya spacetime in massive gravity. The Vainshtein and dRGT mechanisms are used to obtain a ghost free massive gravity, and construct such time dependent solutions. Singularities formed, their nature and strength will be studied in detail. We will also study the thermodynamical aspects of such a geometry by calculating the important thermodynamical quantities for such a system, and analyzing the thermodynamical behavior of such quantities. © 2018 IOP Publishing Ltd and Sissa Medialab.

AUTHOR KEYWORDS: GR black holes; modified gravity

PUBLISHER: Institute of Physics Publishing

DOI: 10.1016/j.dark.2018.02.006

In this paper, we obtain a holographic model of dark energy using the fluid/gravity duality. This model will be dual to a higher dimensional Schwarzschild black hole, and we would use fluid/gravity duality to relate to the parameters of this black hole to such a cosmological model. We will also analyze the thermodynamics of such a solution, and discuss the stability model. Finally, we use cosmological data to constraint the parametric space of this dark energy model. Thus, we will use observational data to perform cosmography for this holographic model based on fluid/gravity duality. © 2018 Elsevier B.V.

AUTHOR KEYWORDS: Black hole; Cosmography; Cosmology; Dark energy; Fluid/gravity duality

PUBLISHER: Elsevier B.V.

DOI: 10.1007/s10773-017-3612-3

In this work, we consider rotating BTZ black hole in three dimensions which is dual of one dimensional holographic superconductors. We applied higher order corrections of the entropy, which interpreted as quantum corrections, to the thermodynamics quantities and study modified thermodynamics. We investigate stability of rotating BTZ black hole under effects of higher order quantum corrections, and find that they affect stability of black hole. So, the small black hole has some instabilities and critical points due to the quantum effects. We also study effect of correction terms on the dual picture of rotating BTZ black hole. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.

AUTHOR KEYWORDS: Black hole; Quantum information; Statistical fluctuations; Thermodynamics

PUBLISHER: Springer New York LLC

DOI: 10.1016/j.nuclphysb.2018.01.018

In this paper, we would like to obtain quantum gravity effects by using Hořava–Lifshitz black hole. We consider logarithmic corrected thermodynamics quantities and investigate the effects of logarithmic correction term. Logarithmic correction comes from thermal fluctuation and may be interpreted as quantum loop corrections. As black hole is a gravitational system, hence we can investigate quantum gravity effect. We find such effects on the black hole stability and obtain domain of correction coefficient. © 2018 The Author(s)

PUBLISHER: Elsevier B.V.

DOI: 10.1016/j.dark.2018.02.001

In this paper, we study the effects of super-light brane world perturbative modes on structure formation in our universe. As these modes modify the large distance behavior of Newtonian potential, they effect the clustering of a system of galaxies. So, we explicitly calculate the clustering of galaxies interacting through such a modified Newtonian potential. We use a suitable approximation for analyzing this system of galaxies, and discuss the validity of such approximations. We observe that such corrections also modify the virial theorem for such a system of galaxies. © 2018 Elsevier B.V.

AUTHOR KEYWORDS: Galaxy clustering; Modified potential

PUBLISHER: Elsevier B.V.

DOI: 10.1142/S0218271818500256

In this paper, we investigate the effects of noncommutative phase-space on the quintom cosmological model. In that case, we discuss about some cosmological parameters and show that they depend on the deformation parameters. We find that the noncommutative parameter plays important role which helps to re-arrange the divergency of cosmological constant. We draw time-dependent scale factor and investigate the effect of noncommutative parameters. Finally, we take advantage from noncommutative phase-space and obtain the deformed Lagrangian for the quintom model. In order to discuss some cosmological phenomena as dark energy and inflation, we employ Noether symmetry. © 2018 World Scientific Publishing Company.

AUTHOR KEYWORDS: deformed spacetime; Noether symmetry; noncommutativity; Quintom cosmology

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1139/cjp-2017-0550

In this paper we consider higher-order corrections of the BTZ and anti-de Sitter Schwarzschild black holes' entropy and study corrected thermodynamics. We obtain some important thermodynamics quantities like internal and Helmholtz free energy and calculate specific heat. By using corrected specific heat we study black holes' stability and investigate possible phase transition and critical points. Correction terms of the entropy are important when the size of a black hole is small and come from thermal fluctuations of statistical physics, hence one can interpret them as quantum corrections to the black hole thermodynamics. We show that the presence of corrections of entropy are very important for stability or instability of black holes. © 2018 Published by NRC Research Press.

AUTHOR KEYWORDS: Black hole; Quantum corrections; Statistics; Thermal fluctuations; Thermodynamics

INDEX KEYWORDS: Entropy; Free energy; Phase transitions; Specific heat; Stars; Statistical Physics; Statistics; Thermodynamics, Black Hole physics; Black hole thermodynamics; Black holes; Correction terms; Higher-order; Quantum correction; Schwarzschild; Thermal fluctuations, Gravitation

PUBLISHER: Canadian Science Publishing

DOI: 10.1142/S0218271819500275

We study the thermodynamics of galactic clustering under the higher-order corrected Newtonian dynamics. The clustering of galaxies is considered as a gravitational phase transition. In order to study the effects of higher-order correction to the thermodynamics of gravitational system, we compute more exact equations of state. Moreover, we investigate the corrected probability distribution function for such a gravitating system. A relation between order parameter and the critical temperature is also established. © 2019 World Scientific Publishing Company.

AUTHOR KEYWORDS: distribution function; large scale structure; Modified gravity; thermodynamics

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1093/mnras/stx2945

Based on thermodynamics, we discuss the galactic clustering of expanding Universe by assuming the gravitational interaction through the modified Newton's potential given by f(R) gravity. We compute the corrected N-particle partition function analytically. The corrected partition function leads to more exact equations of state of the system. By assuming that the system follows quasi-equilibrium, we derive the exact distribution function that exhibits the f(R) correction. Moreover, we evaluate the critical temperature and discuss the stability of the system. We observe the effects of correction of f(R) gravity on the power-law behaviour of particle-particle correlation function also. In order to check the feasibility of an f(R) gravity approach to the clustering of galaxies, we compare our results with an observational galaxy cluster catalogue. © 2017 The Author(s).

AUTHOR KEYWORDS: Cosmology: theory; Dark energy; Large-scale structure of Universe; Methods: analytical; Methods: data analysis

PUBLISHER: Oxford University Press

DOI: 10.1007/s10714-017-2315-7

In this paper, we consider higher order corrections of the entropy, which coming from thermal fluctuations, and find their effect on the thermodynamics of higher dimensional charged black holes. Leading order thermal fluctuation is logarithmic term in the entropy while higher order correction is proportional to the inverse of original entropy. We calculate some thermodynamics quantities and obtain the effect of logarithmic and higher order corrections of entropy on them. Validity of the first law of thermodynamics investigated and Van der Waals equation of state of dual picture studied. We find that five-dimensional black hole behaves as Van der Waals, but higher dimensional case have not such behavior. We find that thermal fluctuations are important in stability of black hole hence affect unstable/stable black hole phase transition. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.

AUTHOR KEYWORDS: Higher dimensional black hole; Thermal fluctuations; Thermodynamics; Van der Waals fluid

PUBLISHER: Springer New York LLC

DOI: 10.1140/epjc/s10052-017-5338-z

In this paper, we consider a deformed STU model in four dimensions including both electric and magnetic charges. Using the AdS/CFT correspondence, we study holographic superconductors and obtain transport properties like electrical and thermal conductivities. We obtain transport properties in terms of the magnetic charge of the black hole and interpret it as the magnetic monopole of dual field theory. We find that the presence of the magnetic charge is necessary to have maximum conductivities, and the existence of a magnetic monopole with a critical charge (137 e) to reach the maximum superconductivity is important. Also, we show that the thermal conductivity increases with increasing of the magnetic charge. It may be concluded that the origin of superconductivity is the magnetic monopole. © 2017, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1016/j.physletb.2017.08.046

In this work, we shall analyze the effects of quantum fluctuations on the properties of a BTZ black hole, in a massive theory of gravity. We will analyze this for a charged BTZ black hole in asymptotically AdS and dS space–times. The quantum fluctuations would produce thermal fluctuations in the thermodynamics of this BTZ black hole. As these fluctuations would become relevant at a sufficiently small scale, we shall discuss the effects of such thermal fluctuations on the entropy of a small charged BTZ black. We shall also analyze the effects of these fluctuations on the stability of such a black hole. © 2017 The Author(s)

AUTHOR KEYWORDS: Black hole; Massive gravity; Thermodynamics

PUBLISHER: Elsevier B.V.

DOI: 10.5506/APhysPolB.48.1507

In this article, we study Langevin diffusion coefficients for the fivedimensional N = 2 STU model in the presence of higher derivative corrections. We obtained the effect of black hole charge, corresponding to the chemical potential, on the Langevin diffusion coefficients ratio. We confirm universal behavior of transverse-to-longitudinal ratio of coefficients.

INDEX KEYWORDS: Black holes; Higher derivatives; Langevin; Longitudinal ratio; Universal behaviors, Diffusion

PUBLISHER: Jagellonian University

DOI: 10.1140/epjc/s10052-017-5125-x

In this paper, we study the effect of thermal fluctuations on the thermodynamics of a black geometry with hyperscaling violation. These thermal fluctuations in the thermodynamics of this system are produced from quantum corrections of geometry describing this system. We discuss the stability of this system using specific heat and the entire Hessian matrix of the free energy. We will analyze the effects of thermal fluctuations on the stability of this system. We also analyze the effects of thermal fluctuations on the criticality of the hyperscaling-violation background. © 2017, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1007/s10773-017-3377-8

AUTHOR KEYWORDS: Holography; QCD

PUBLISHER: Springer New York LLC

DOI: 10.1142/S0217751X17500452

In this paper, we consider a deformed AdS background and study the effect of deformation parameter on the pair production rate of the Schwinger effect. The electrostatic potential is important for the pair production in the holographic Schwinger effect. In this paper, we analyze the electrostatic potential in a deformed AdS background and investigate the effect of deformation parameter which may be useful to test the AdS/QCD. In the case of zero temperature, we find that the larger value of the deformation parameter leads to a smaller value of separation length of the test particles on the probe. Also, we find a finite maximum of separation length in the presence of modification parameter. © 2017 World Scientific Publishing Company.

AUTHOR KEYWORDS: AdS/CFT; QCD; QED; Schwinger effect

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1142/S0218271817500122

In this paper, we consider tachyonic matter in spatially flat Friedmann-Robertson-Walker (FRW) universe, and obtain behavior of some important cosmological parameters for two special cases of potentials. First, we assume the exponential potential and then consider hyperbolic cosine type potential. In both cases, we obtain behavior of the Hubble, deceleration and EoS parameters. Comparison with observational data suggest the model with hyperbolic cosine type scalar field potentials has good model to describe universe. © 2017 World Scientific Publishing Company.

AUTHOR KEYWORDS: cosmology; Dark energy

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1140/epjc/s10052-017-4665-4

In this paper, we analyze the effects of thermal fluctuations on a STU black hole. We observe that these thermal fluctuations can affect the stability of a STU black hole. We will also analyze the effects of these thermal fluctuations on the thermodynamics of a STU black hole. Furthermore, in the Jacobson formalism such a modification will produce a deformation of the geometry of the STU black hole. Hence, we use the AdS/CFT correspondence to analyze the effect of such a deformation on the dual quark–gluon plasma. So, we explicitly analyze the effect of thermal fluctuations on the shear viscosity to entropy ratio in the quark–gluon plasma, and we analyze the effects of thermal fluctuations on this ratio. © 2017, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1016/j.aop.2016.11.014

We propose a method to test the effects of quantum fluctuations on black holes by analyzing the effects of thermal fluctuations on dumb holes, the analogs for black holes. The proposal is based on the Jacobson formalism, where the Einstein field equations are viewed as thermodynamical relations, and so the quantum fluctuations are generated from the thermal fluctuations. It is well known that all approaches to quantum gravity generate logarithmic corrections to the entropy of a black hole and the coefficient of this term varies according to the different approaches to the quantum gravity. It is possible to demonstrate that such logarithmic terms are also generated from thermal fluctuations in dumb holes. In this paper, we claim that it is possible to experimentally test such corrections for dumb holes, and also obtain the correct coefficient for them. This fact can then be used to predict the effects of quantum fluctuations on realistic black holes, and so it can also be used, in principle, to experimentally test the different approaches to quantum gravity. © 2016 Elsevier Inc.

AUTHOR KEYWORDS: Black holes; Dumb holes; Quantum gravity; Thermal fluctuations

PUBLISHER: Academic Press Inc.

DOI: 10.1103/PhysRevD.95.106014

We consider a massive gravity black hole in four-dimensional anti-de Sitter space and study the effect of thermal fluctuations on the thermodynamics of the black hole. We consider thermal fluctuations as logarithmic correction terms in the entropy. We analyze the effect of logarithmic correction on thermodynamics potentials like Helmholtz and Gibbs which are found decreasing functions. We study critical points and stability and find that the presence of logarithmic correction is necessary to have stable phase and critical point. © 2017 American Physical Society.

PUBLISHER: American Physical Society

DOI: 10.1016/j.nuclphysb.2016.10.013

In this paper, we will analyze the thermodynamics of a small singly spinning Kerr-AdS black hole. As the black hole will be sufficient small, its temperature will be large and so we can not neglect the effects of thermal fluctuations. We will demonstrate that these thermal fluctuations correct the entropy of singly spinning Kerr-AdS black hole by a logarithmic correction term. We will analyze the implications of the logarithmic correction on other thermodynamic properties of this black hole, and analyze the stability of such a black hole. We will observe that this form of correction becomes important when the size of the black hole is sufficient small. We will also analyze the effect of these thermal fluctuations on the critical phenomena for such a black hole. © 2016 The Author(s)

PUBLISHER: Elsevier B.V.

DOI: 10.1103/PhysRevD.94.064006

In this paper, we consider a dyonic charged anti-de Sitter black hole, which is a holographic dual of a van der Waals fluid. We use logarithm-corrected entropy and study thermodynamics of the black hole and show that holographic picture is still valid. Critical behaviors and stability are also discussed. Logarithmic corrections arises due to thermal fluctuations, which are important when the size of black hole is small. So, thermal fluctuations are interpreted as a quantum effect. It means that we can see the quantum effect of a black hole, which is a gravitational system. © 2016 American Physical Society.

PUBLISHER: American Physical Society

Pourhassan, B. Extended Chaplygin gas in Horava-Lifshitz gravity (2016) 13, pp. 132-138.

DOI: 10.1016/j.dark.2016.06.002

In this paper, we investigate cosmological models of the extended Chaplygin gas in a universe governed by Horava-Lifshitz gravity. The equation of state for an extended Chaplygin gas is a (n+2)-variable equation determined by An, α, and B. In this work, we are interested to the case of second order (n=2) equation of state which recovers quadratic barotropic equation of state. In that case there are four free parameters. We solve conservation equation approximately and obtain energy density in terms of scale factor with mentioned free parameters. Under some assumptions we relate free parameters to each other to have only one free independent parameter (A2). It help us to obtain explicit expression for energy density in terms of scale factor. The allowed values of the second order extended Chaplygin gas parameter is fixed using the recent astrophysical and cosmological observational data. Thermodynamics of the model investigated based on the first and second law of thermodynamics. © 2016.

AUTHOR KEYWORDS: Chaplygin gas; Dark energy; Horava-Lifshitz

PUBLISHER: Elsevier

DOI: 10.1007/s10773-016-3012-0

In this letter, relativistic infinitely extended particles formulated. Correct form of action with possibility of reparametrization obtained and effect of electric field considered. It may be one of the first step to re-introduce theory of every things given by Nakano and Hessaby many years ago. © 2016, Springer Science+Business Media New York.

AUTHOR KEYWORDS: Particle physics; Unified theory

PUBLISHER: Springer New York LLC

DOI: 10.1142/S0218271816500772

In this paper, we consider an inflationary model of f(R) gravity with polynomial form plus logarithmic term. We calculate some cosmological parameters and compare our results with the Planck 2015 data. We find that presence of both logarithmic and polynomial corrections is necessary to yield slow-roll condition. Also, we study critical points and stability of the model to find that it is a viable model. © 2016 World Scientific Publishing Company.

AUTHOR KEYWORDS: inflation; Modified gravity; Planck data

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1016/j.physletb.2016.02.043

In this paper, we will analyze the effect of thermal fluctuations on the thermodynamics of a charged dilatonic black Saturn. These thermal fluctuations will correct the thermodynamics of the charged dilatonic black Saturn. We will analyze the corrections to the thermodynamics of this system by first relating the fluctuations in the entropy to the fluctuations in the energy. Then, we will use the relation between entropy and a conformal field theory to analyze the fluctuations in the entropy. We will demonstrate that similar physical results are obtained from both these approaches. We will also study the effect of thermal fluctuations on the phase transition in this charged dilatonic black Saturn. © 2016 The Authors.

PUBLISHER: Elsevier

DOI: 10.1139/cjp-2016-0154

The universe evolution from inflation to late-time acceleration is investigated in a unified way, using a two-component fluid constituted from extended Chaplygin gas alongside a phantom scalar field. We extract solutions for the various cosmological eras, focusing on the behavior of the scale factor, the various density parameters and the equation-of-state parameter. Furthermore, we extract and discuss bouncing solutions. Finally, we examine the perturbations of the model, ensuring their stability and extracting the predictions for the tensor-to-scalar ratio. © 2016 Published by NRC Research Press.

AUTHOR KEYWORDS: Chaplygin gas; Dark energy; FRW cosmology; Phantom field

INDEX KEYWORDS: Equations of state; Slip forming, Chaplygin gas; Dark energy; Equation of state; Extract solutions; Phantom field; Scalar fields; Universe evolution; Various densities, Cosmology

PUBLISHER: Canadian Science Publishing

DOI: 10.1142/S0217732316500577

In this paper, we consider the Klein-Gordon equation in a 3D charged rotating hairy black hole background to study behavior of a massive scalar field. In the general case, we find periodic-like behavior for the scalar field which may vanish at the black hole horizon or far from the black hole horizon. For the special cases of non-rotating or near horizon approximation, we find radial solution of Klein-Gordon equation in terms of hypergeometric and Kummer functions. Also for the case of uncharged black hole, we find numerical solution of the Klein-Gordon equation as periodic function which may enhance out of the black hole or vanish at horizon. We find allowed boundary conditions which may yield to the identical bosons described by scalar field. © 2016 World Scientific Publishing Company.

AUTHOR KEYWORDS: Black hole; scalar field

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1140/epjc/s10052-016-3998-8

In this work, we analyze the effects of thermal fluctuations on the thermodynamics of a modified Hayward black hole. These thermal fluctuations will produce correction terms for various thermodynamical quantities like entropy, pressure, internal energy, and specific heats. We also investigate the effect of these correction terms on the first law of thermodynamics. Finally, we study the phase transition for the modified Hayward black hole. It is demonstrated that the modified Hayward black hole is stable even after the thermal fluctuations are taken into account, as long as the event horizon is larger than a certain critical value. © 2016, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1016/j.physletb.2015.10.077

In this paper, we will analyze the effects of thermal fluctuations on the stability of a black Saturn. The entropy of the black Saturn will get corrected due to these thermal fluctuations. We will demonstrate that the correction term generated by these thermal fluctuations is a logarithmic term. Then we will use this corrected value of the entropy to obtain bounds for various parameters of the black Saturn. We will also analyze the thermodynamical stability of the black Saturn in presence of thermal fluctuations, using this corrected value of the entropy. © 2015 The Authors.

PUBLISHER: Elsevier

DOI: 10.1103/PhysRevD.92.103511

In this paper, we consider an inflationary model that effectively behaves as a modified Chaplygin gas in the context of quintessence cosmology. We reconstruct the inflaton potential from the bottom up and using the recent observational data we fix the free parameters of the model. We show that the modified Chaplygin gas-inspired model is suitable for both the early and the late time acceleration but has shortcomings between the two periods. © 2015 American Physical Society.

PUBLISHER: American Physical Society

DOI: 10.1007/s10773-015-2564-8

In this paper, we consider an unusual connection between different fluids. Having established a research goal we would like to consider a toy model of the Universe and investigate its behavior, especially for later time evolution for well known facts. The main goal of the article is to consider a toy model of the Universe with generalized ghost dark energy, Van der Waals gas and a phenomenologically modified fluid. The origin of the last component can be understood as a result of interaction between some original fluid and some source of energy or matter in Universe. By unusual connection we mean an assumption that generalized ghost dark energy has its contribution to the model by an interaction term Q and we suppose an interaction of the form Q=3Hb(ρtot−ρGDe). Graphical analysis is performed and the questions of validity of the generalized second law of thermodynamics and stability of the model also approached in this paper. © 2015, Springer Science+Business Media New York.

AUTHOR KEYWORDS: Ghost dark energy; Modified fluid models; Van der Waals fluid

PUBLISHER: Springer New York LLC

DOI: 10.1209/0295-5075/111/40006

In this paper, we will analyze the effects of thermal fluctuations on a charged anti-de Sitter (AdS) black hole. This will be done by analyzing the corrections to black-hole thermodynamics due to these thermal fluctuations. We will demonstrate that the entropy of this black hole gets corrected by a logarithmic term. We will also calculate other corrections to other important thermodynamic quantities for this black hole. Finally, we will use the corrected value of the specific heat to analyze the phase transition in this system. © CopyrightEPLA, 2015.

PUBLISHER: Institute of Physics Publishing

DOI: 10.1140/epjp/i2015-15084-6

In this paper, we study the holographic dark energy density and interacting extended Chaplygin gas energy density in the Einstein gravity. We reconstruct the scalar field and the scalar potential describing the extended Chaplygin gas. In the special case, we obtain energy density and investigate some cosmological parameters. Assuming interaction between components we find energy density for some different parametrization of total EoS. We analyze tensor-to-scalar ratio and use recent observational data of BICEP2 to fix the model parameters. © 2015, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

PUBLISHER: Springer Verlag

DOI: 10.1142/S0217732315500704

In this paper, we consider a universe dominated by the extended Chaplygin gas which was recently proposed as the last version of Chaplygin gas models. Here, we only consider the second-order term which recovers quadratic barotropic fluid equation of state. The density perturbations are analyzed in both relativistic and Newtonian regimes and show that the model is stable without any phase transition and critical point. We confirmed stability of the model using thermodynamics point of view. © 2015 World Scientific Publishing Company.

AUTHOR KEYWORDS: Cosmology; dark energy

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1139/cjp-2014-0283

In this paper, we study three models of f(R) modified gravity including higher order terms based on different equation of state parameters. We also assume variable G and Λ. Using numerical analysis, we obtain the behavior of some important cosmological parameters, like the Hubble expansion H parameter and the deceleration parameter q. Statefinder diagnostics are also performed for all models. © 2015 Published by NRC Research Press.

INDEX KEYWORDS: Cosmological parameters; Equation of state; H-parameter; Higher derivatives; Higher order terms; Three models, Equations of state

PUBLISHER: National Research Council of Canada

DOI: 10.1007/s10509-014-2209-z

In this paper, we consider an effective quintessence scalar field with a power-law potential interacting with a Pb=ξqρb barotropic fluid as a first model, where q is a deceleration parameter. For the second model we assume viscous polytropic gas interacting with the scalar field. We investigate problem numerically and analyze behavior of different cosmological parameter concerning to components and behavior of Universe. We also compare our results with observational data to fix parameters of the models. We find some instabilities in the first model which may disappear in the second model for the appropriate parameters. Therefore, we can propose interacting quintessence dark energy with viscous polytropic gas as a successful model to describe Universe. © 2014, Springer Science+Business Media Dordrecht.

AUTHOR KEYWORDS: Cosmology; Dark energy; Quintessence field

PUBLISHER: Kluwer Academic Publishers

DOI: 10.1140/epjc/s10052-015-3263-6

In this paper, we study two different models of dark energy based on the Chaplygin gas equation of state. The first model is the variable modified Chaplygin gas, while the second one is the extended Chaplygin gas. Both models are considered in the framework of higher order f(R) modified gravity. We also consider the case of time-varying gravitational constant G and Λ for both models. We investigate some cosmological parameters such as the Hubble, the deceleration, and the equation of state parameters. Then we show that the model that we consider, the extended Chaplygin gas with time-dependent G and Λ, is consistent with the observational data. Finally we conclude with the discussion of cosmological perturbations of our model. © 2015, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1088/0253-6102/62/3/12

In this paper, we construct rotating charged hairy black hole in (2+1) dimensions for infinitesimal black hole charge and rotation parameters. Then we consider this black hole as particle accelerator and calculate the center-of-mass energy of two colliding test particles near the rotating charged hairy black hole in (2+1) dimensions. As we expected, the center-of-mass energy has infinite value. © 2014 Chinese Physical Society and IOP Publishing Ltd.

AUTHOR KEYWORDS: 3D black hole; particle acceleration; thermodynamics

PUBLISHER: Institute of Physics Publishing

DOI: 10.1007/s10773-014-2036-6

In this paper we consider two models of quintessence scalar fields with different potentials. Interaction with generalized cosmic Chaplygin gas is also investigated. Cosmological parameters are studied and graphical behavior is analyzed. We find that our model is agree with observational data specially ΛCDM model. © 2014, Springer Science+Business Media New York.

AUTHOR KEYWORDS: Cosmology; Dark energy; Quintessence

PUBLISHER: Springer New York LLC

DOI: 10.1140/epjc/s10052-014-2793-7

In this paper, we investigate the dynamics of a heavy quark for plasmas corresponding to three dimensional hairy black holes. We utilize the AdS/CFT correspondence to study the holographic Brownian motion of this particle with different kinds of hairy black holes. For an uncharged black hole in the low frequency limit we derive analytic expressions for the correlation functions and the response functions and verify that the fluctuation–dissipation theorem holds in the presence of a scalar field against a metric background. In the case of a charged black hole, we think that the results are similar to that derived for an uncharged black hole. © 2014, The Author(s).

PUBLISHER: Springer New York LLC

DOI: 10.1007/s10773-014-2145-2

In this paper, we consider effective Hamiltonian of 2D dilatonic black hole adding Axion field and calculate closed 2-form by using geometric prequantization method. It yields to the Schrödinger equation which may be solved to obtain wave function. We obtained a condition on the cosmological constant to obtain appropriate Hamilton equation of motions. © 2014, Springer Science+Business Media New York.

AUTHOR KEYWORDS: 2D black hole; Effective Hamiltonian; Prequantization

PUBLISHER: Springer New York LLC

DOI: 10.1007/s10773-014-2106-9

In this paper we consider Kerr-Gödel black hole and study thermodynamics and statistics. We analyze some important quantities such as free energy, specific heat, and partition function numerically. We compare thermodynamics entropy with statistics entropy and find agreement between them. © 2014 Springer Science+Business Media New York.

AUTHOR KEYWORDS: Black hole; Statistics; Thermodynamics

PUBLISHER: Springer New York LLC

DOI: 10.1142/S0219887814500613

In this paper, we consider Universe filled with two-component fluid. We study two different models. In the first model we assume barotropic fluid with the linear equation of state (EoS) as the first component of total fluid. In the second model we assume van der Waals gas as the first component of total fluid. In both models, the second component assumed generalized ghost dark energy. We consider also interaction between components and discuss, numerically, cosmological quantities for two different parametrizations of EoS which varies with time. We consider this as a toy model of our Universe. We fix parameters of the model by using generalized second law of thermodynamics. Comparing our results with some observational data suggests interacting barotropic fluid with EoS parameter ω(t)=ω0cos(tH)+ω1t H/H and generalized ghost dark energy as an appropriate model to describe our Universe. © 2014 World Scientific Publishing Company.

AUTHOR KEYWORDS: cosmology; Dark energy; early Universe

PUBLISHER: World Scientific Publishing Co. Pte Ltd

DOI: 10.1155/2014/965694

We review the oscillator with Aharonov-Casher system and study some mathematical foundation about factorization method. The factorization method helps us to obtain the energy spectrum and general wave function for the corresponding system in some spin condition. The factorization method leads us to obtain the raising and lowering operators for the Aharonov-Casher system. The corresponding operators give us the generators of the algebra. © 2014 J. Sadeghi et al.

PUBLISHER: Hindawi Publishing Corporation

DOI: 10.1139/cjp-2014-0229

We consider a charged black hole with a scalar field that is coupled to gravity in (2 + 1)-dimensions. We compute the logarithmic corrections to the corresponding system using two approaches. In the first method we take advantage of thermodynamic properties. In the second method we use the metric function that is suggested by conformal field theory. Finally, we compare the results of the two approaches. © 2014 Published by NRC Research Press.

INDEX KEYWORDS: Gravitation, Black holes; Conformal field theories; Logarithmic corrections; Scalar fields, Stars

PUBLISHER: National Research Council of Canada