Khodadad Kokabi

Assistant Professor of Astronomy and Astrophysics

Selected Publications

Pourhassan, B., Kokabi, K., Sabery, Z. Higher order corrected thermodynamics and statistics of Kerr–Newman–Gödel black hole (2018) 399, pp. 181-192.

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.

Pourhassan, B., Kokabi, K. Higher Order Quantum Corrections of Rotating BTZ Black Hole (2018) 57 (3), pp. 780-791.

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

Pourhassan, B., Kokabi, K. Effects of higher-order corrected entropy on the black hole physics (2018) 96 (3), pp. 262-267.

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

Pourhassan, B., Kokabi, K., Rangyan, S. Thermodynamics of higher dimensional black holes with higher order thermal fluctuations (2017) 49 (12), art. no. 144, .

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

Aghili, P., Kokabi, K. Effect of magnetic field on the rotating filamentary molecular clouds (2017) 362 (4), art. no. 64, .

DOI: 10.1007/s10509-017-3042-y

The Purpose of this work is to study the evolution of magnetized rotating filamentary molecular clouds. We consider cylindrical symmetric filamentary molecular clouds at an early stage of evolution. For the first time we consider the rotation of filamentary molecular in the presence of an axial and azimuthal magnetic field without any assumption of density and magnetic functions. We show that in addition to decreasing the radial collapse velocity, the rotational velocity is also affected by the magnetic field. The existence of rotation yields fragmentation of filaments. Moreover, we show that the magnetic field has a significant effect on the fragmentation of filamentary molecular clouds. © 2017, Springer Science+Business Media Dordrecht.

AUTHOR KEYWORDS: Filamentary molecular clouds; Magnetic field; Rotation
PUBLISHER: Springer Netherlands

Khesali, A., Kokabi, K., Faghei, K., Nejad-Asghar, M. Evolution of filamentary molecular clouds in the presence of magnetic fields (2014) 14 (1), pp. 66-76.

DOI: 10.1088/1674-4527/14/1/005

The purpose of this paper is to explore the effect of magnetic fields on the dynamics of magnetized filamentary molecular clouds. We suppose there is a filament with cylindrical symmetry and two components of axial and toroidal magnetic fields. In comparison to previous works, the novelty in the present work involves a similarity solution that does not define a function of the magnetic fields or density. We consider the effect of the magnetic field on the collapse of the filament in both axial and toroidal directions and show that the magnetic field has a braking effect, which means that the increasing intensity of the magnetic field reduces the velocity of collapse. This is consistent with other studies. We find that the magnetic field in the central region tends to be aligned with the filament axis. Also, the magnitude and the direction of the magnetic field depend on the magnitude and direction of the initial magnetic field in the outer region. Moreover, we show that more energy dissipation from the filament causes a rise in the infall velocity. © 2014 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.

AUTHOR KEYWORDS: ISM: clouds; ISM: magnetic fields