arXiv subjects

Sareh Eslamzadeh

Publications and source records attributed to Sareh Eslamzadeh.

7 recordsLinked to original sources

arXiv2025

Thermodynamic analysis of a compact object in Rastall-Rainbow gravity

In this paper, we investigate the thermodynamic behavior of a horizonless compact object within the framework of Rastall-Rainbow (RR) gravity. Working with local shell thermodynamics for gravastar and an exterior fiducial temperature, we show that the RR modification bends temperature to produce two extrema and a stable mass remnant at zero temperature. We show that the gravastar's shell entropy is smaller than that of a comparable black hole, and that RR modifications introduce a logarithmic correction which contributes to specific heat positivity and a smoother free energy landscape of small gravastars. A Central finding of this work is that, from heat capacity and Helmholtz free energy analyses, we uncover small, middle, and large branches and demonstrate that unlike Rainbow modified black holes, the small RR gravastar is both locally and globally favored over hot curved space. At the parameter level, both Rastall and Rainbow play distinct roles. Increasing the Rastall parameter, by strengthening matter-curvature coupling, adjusts the redshift between the shell and the exterior, shifts the temperature maximum to higher values at larger masses, and narrows the unstable window. In contrast, increasing the Rainbow parameter enhances energy dependent UV suppression and bends the temperature in lower values at larger masses. Altogether, these results highlight a controlled route to thermodynamic stabilization and the emergence of a stable remnant in horizonless compact objects within RR gravity.

gr-qc↗

arXiv2025

A Brief Review of Quantum Tunneling: Computational Approaches and Experimental Evidence

This paper presents a concise review of the quantum tunneling approach to Hawking radiation, covering its theoretical foundations, extensions, and experimental efforts. We begin by outlining the Hamilton-Jacobi and Parikh-Wilczek methods, which provide a semi-classical framework for deriving Hawking radiation from stationary black holes. The discussion is then extended to dynamical black holes, where evolving horizons require modified treatments incorporating trapping horizons, Kodama vectors, and dynamical surface gravity. We explored the possible tunneling paths for particles crossing the horizon in dynamical black holes and emphasized the crucial role of the imaginary part of the action in determining the Hawking temperature. In the second part, we review experimental investigations of Hawking radiation, including analogue black hole experiments, quantum simulations, and astrophysical searches for primordial black hole evaporation. While no direct detection of Hawking radiation has been achieved, recent advances in Bose-Einstein condensates, optical analogues, and superconducting qubits offer indirect support for the tunneling interpretation of black hole evaporation.

gr-qc↗

arXiv2025

History of a Particle Bounded to the Cosmological LTB Black Hole Surrounded by the Quintom Field

In this paper, we derived the complete set of time-dependent geodesic equations for an LTB black hole surrounded by a Quintom field and investigated the evolution of effective potential and photon orbits across cosmic epochs. Our findings demonstrate that in an accelerated universe, the peak of an effective potential decreases in height and shifts toward smaller radii. Additionally, the probability of stable orbit formation decreases as cosmic expansion progresses. We classified the possible trajectories into four types: terminating bound orbits, stable orbits, scattering flyby orbits, and terminating escape orbits. The results indicate that stable bound orbits are more prevalent in the early universe, whereas at late time epochs, flyby orbits become dominant due to the expansion-driven weakening of gravitational potential. We further analyzed the impact of angular momentum on the evolution of orbits, showing that as it increases, the ISCO radius decreases while the peak of the effective potential shifts outward. This suggests that particles with higher angular momentum follow extended bound orbits, and more energetic photons are more likely to be captured by the black hole. Conversely, an increase in angular momentum reduces the probability of flyby orbits while increasing the likelihood of direct fall into the black hole. Our study provides new insights into how cosmic acceleration influences black hole geodesics, revealing that the progressive shrinking of ISCO and stable orbits eventually disappear as the universe approaches the Big Rip singularity. These findings contribute to a deeper understanding of the dynamical nature of cosmological black holes and may offer new perspectives for observational tests through gravitational lensing, accretion disk evolution, and quasi-periodic oscillations (QPOs) in evolving black hole spacetimes.

gr-qc↗

arXiv2024

Holographic Thermodynamics of an Enhanced Charged AdS Black Hole in String Theory's Playground

In this paper, we consider an $α^{\prime}$ corrected Reissner-Nordström AdS black hole to study thermodynamics. We study the $P-V$ criticality and thermodynamical stability of the black hole. We obtained a first-order phase transition, which may be interpreted as the large/small black hole phase transition. Therefore, we obtained a van der Waals behaviour and obtained critical points. Finally, we calculate quantum work used to resolve the information loss paradox.

hep-th↗

arXiv2023

Cosmological LTB Black Hole in a Quintom Universe

We study cosmological Lemaitre-Tolman-Bondi (LTB) black hole thermodynamics immersed in a quintom universe. We investigate some thermodynamic aspects of such a black hole in detail. We apply two methods of treating particles' tunneling from the apparent horizons and calculate the black hole's temperature in each method; the results of which are the same. In addition, by considering specific time slices in cosmic history, we study the thermodynamic features of this black hole in these specific cosmic epochs. Also, we discuss the information loss problem and the remnant content of the cosmological black hole in different cosmic epochs in this context. We show that approximately in all cosmic history, the temperature of the black hole's apparent horizon is more than the temperature of the cosmological apparent horizon.

gr-qc↗

arXiv2022

Hawking Temperature for 4D-Einstein-Gauss-Bonnet Black Holes from uncertainty principle

Inspired by string theory, Heisenberg's uncertainty principle can be generalized to include the photon-electron gravitational interaction, which leads to the Generalized Uncertainty Principle (GUP). Although GUP considers gravitational uncertainty at the minimum fundamental length scale in physics, it does not consider the effects of spacetime curvature on quantum mechanical uncertainty relations. The Extended Uncertainty Principle (EUP) is a generalization of Heisenberg's Uncertainty Principle that, unlike the GUP, applies to large length scales. GEUP is also a linear combination of EUP and GUP that creates minimal uncertainty on large length scales. The Einstein-Gauss-Bonnet theory (EGB) can be considered as one of the most promising candidates for modified gravity. In this paper, by using GUP, EUP, and GEUP, we intend to obtain the Hawking temperature of a four-dimensional EGB black hole in the asymptotically flat and (Anti)-de Sitter spacetime. We show that coupling constant, cosmological constant, mass, and radius significantly affect Hawking temperature and decrease or increase Hawking temperature depending on the chosen horizons.

gr-qc↗

arXiv2022

Radiation from Einstein-Gauss-Bonnet de Sitter Black Hole via Tunneling Process

In this paper, we probe in 4D Einstein-Gauss-Bonnet black hole and its thermodynamics. We illustrate the three asymptotically 4D EGB spacetime as an asymptotically flat, de Sitter, and Anti-de Sitter. Also, we apply the tunneling of the massless particles from the horizon of 4D EGB gravity and we investigate the correlation between the emission modes and temperature of the horizon. In asymptotically flat spacetime, the existence of the coupling constant alone constructs the regular spacetime, the radiation deviates from the pure thermal, and the temperature of the black hole horizon would be zero in the final stage of the black hole evaporation. In Asymptotically de Sitter spacetime, results illustrate that the evolution of the temperatures is in direction of the remaining rest mass with the probably same temperature for the black hole and the cosmological horizon. In addition, the exciting result is that temperature behaviors exactly match with the temperature behaviors of a regular black hole in Lovelock gravity in a higher dimension.

gr-qc↗