arXiv subjects

Yassine Sekhmani

Publications and source records attributed to Yassine Sekhmani.

25 records · Page 2Linked to original sources

arXiv2024

Thermodynamics of the Van der Waals black hole within nonextensive Kaniadiakis entropy

In this work, we have studied the thermodynamic properties of the Van der Waals black hole in the framework of the nonextensive Kaniadakis entropy. We have shown that the black hole properties, such as the mass and temperature, differ from those obtained by using the the Boltzmann-Gibbs approach. Moreover, the nonextensivity \k{appa}-parameter changes behavior of the Gibbs free energy via introduced thermodynamic instabilities, whereas the emission rate is influenced by \k{appa} only at low frequencies. Nonetheless, the pressure-volume (P(V)) characteristics are found independent of \k{appa} and the entropy form, unlike in other anti-de Sitter (AdS) black hole models. In summary, presented findings partially support previous arguments of Gohar and Salzano that under certain circumstances all entropic models are equivalent and indistinguishable [1].

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arXiv2024

Four $\mathbb{S}\mathbb{T}\mathbb{U}$ Black Holes Shadows

In this work, we examine the optical behaviors and thermodynamic phase structures using shadow analysis for four $\mathbb{S}\mathbb{T}\mathbb{U}$ black holes. The study is conducted for four cases of charge configurations on the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$. As a matter of fact, both the electric charge as a parameter and the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$ affect the geometry of the black hole shadow, particularly the size of the shadow. We also introduce a constraint on the charge of the black hole from the observational results of the M87$^\star$ {\color{black}and Sgr A$^\star$} shadow. Furthermore, we show that the electric charge and the parameter space $\mathcal{M}\left(q_1,q_2,q_3,q_4\right)$ have a non-trivial impact on the variation of the energy emission rate. Interestingly enough, we find novel scenarios in which the evaporation is slower, which causes the lifetime of the black holes to be considerably elongated. On the other side, the phase structure of four $\mathbb{S}\mathbb{T}\mathbb{U}$ black holes is explored for two cases of electric charge configuration. The findings show a perfect correlation between the shadow and event horizon radii. This correlation is, in fact, helpful in discovering the phase transition in terms of the shadow radius. In addition, the microstructure is being analyzed in terms of shadow analysis, providing similar behavior to the ordinary situation of the Ruppeiner formalism.

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arXiv2024

Phase structures and critical behaviour of rational non-linear electrodynamics AdS black holes in Rastall gravity

This research paper presents a black hole solution with a rational non-linear electrodynamics source in the Rastall gravity framework. The paper analyzes the thermodynamic properties of the solution in normal phase space and explores its critical behavior. The phase structure is examined using the extended first law of thermodynamics, with the cosmological constant $Λ$ serving as pressure $P$. The isotherms exhibit van der Waals behavior at small values of horizon $r_+$. The paper also investigates the Gibbs free energy behavior and finds two critical points with two pressures where the reentrant phase transition occurs and disappears. On the other hand, we explore the prevalent microstructure of black holes in Ruppeiner geometry, uncovering significant deviations in the nature of particle interactions from conventional practice. Moreover, the thermodynamic geometry is analyzed using the Ruppeiner formalism, with the normalized Ricci scalar indicating possible point-phase transitions of the heat capacity, and the normalized extrinsic curvature having the same sign as the normalized Ricci scalar. The three-phase transitions of the heat capacity are those that we find for the normalized Ruppeiner curvatures. Thus, there is an absolute correspondence.

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arXiv2024

Dark matter effects of a black hole with nonsingular Yukawa-modified potential in Einstein-Gauss-Bonnet Gravity

This paper investigates the contribution of the nonsingular Yukawa-modified potential in the context of four-dimensional Einstein-Gauss-Bonnet (EGB) gravity modeling by a static and spherically symmetric black hole solution. These Yukawa-type corrections are essentially described along two parameters, $β$ and $λ$, affecting Newton's law of gravity at large distances, and a deformation parameter $\ell_0$, which is essential at short distances. Primarily, the strongest effect is encoded in $β$, which alters the total mass of the black hole with additional mass proportional to $β\mathcal{M}$, imitating the effects of dark matter at large distances from the black hole. In contrast, the effect due to $λ$ is small for astrophysical values. On the other hand, the EGB gravity is ruled by the Gauss-Bonnet (GB) coupling constant $α$, a fundamental parameter of the theory. We pay particular attention to thermodynamic stability, critical orbits, geodesics and quasinormal modes. The results demonstrate stability of the black hole solution for a range of values of the GB coupling constant $α$. Furthermore, this study investigates the null geodesic motion, namely the shadow behavior, providing intriguing results in relation to the size of the black hole shadow.

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arXiv2023

Quasinormal Modes and Optical Properties of 4-D black holes in Einstein Power-Yang-Mills Gravity

This paper explores the impact of the Yang-Mills charge parameter and the exponent term on a $4$D black hole solution in the Einstein Power-Yang-Mills theory. Through an investigation of the massless scalar quasinormal mode spectrum, black hole shadow, and emission rate, we have determined that the effects of these two parameters are opposite. Specifically, the Yang-Mills charge parameter causes an increase in the real quasinormal frequencies with a correspondingly smaller damping rate. It also results in a smaller black hole shadow and a lower evaporation rate.

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arXiv2023

Joule-Thomson expansion and Optical behaviour of Reissner-Nordström-Anti-de Sitter black holes in Rastall gravity surrounded by a Quintessence field

This paper deals with the thermodynamics, Joule-Thomson expansion and optical behaviour of a Reissner-Nordström-anti-de Sitter black hole in Rastall gravity surrounded by a quintessence field. The black hole solution obtained in this framework is different from a corresponding black hole in General Relativity. The black hole metric function, as well as the Hawking temperature, is affected by the presence of energy-momentum conservation violation. The presence of energy-momentum conservation violation also affects the isenthalpic and inversion temperature curves, and with an increase in the Rastall parameter, the inversion temperature rises slowly. The impacts of other parameters, such as charge, structural constant etc., are investigated and compared. The black hole shadow, as well as the energy emission rate of the black hole, decreases with an increase in the Rastall parameter. Hence, the black holes evaporate slowly in presence of energy-momentum conservation violation.

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arXiv2023

Electromagnetic Quasinormal modes of Dyonic AdS black holes with quasi-topological electromagnetism in a Horndeski gravity theory mimicking EGB gravity at $D \rightarrow 4$

We investigate some properties of a black hole in a Horndeski gravity theory mimicking Einstein-Gauss-Bonnet (EGB) gravity at $D \rightarrow 4$. Borrowing ideas from quasitopological gravities provide a matter source of dyonic fields, in which the black hole solution carries two charges, electric and magnetic, in the context of the EGB gravity. However, due to several limitations of the EGB gravity in $D \rightarrow 4$, we consider a Horndeski gravity theory which can mimic EGB gravity in $D \rightarrow 4$. The essential practice used in this paper is the electromagnetic quasinormal modes process, with the goal of discovering the spectrum of such an electromagnetic perturbation over the black hole spacetime. The Wentzel-Kramer-Brillouin (WKB) approximation is used to achieve the desired results. The study shows that both the charges have similar impacts on the quasinormal modes.

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