Searcharxiv⌕ Search

arXiv subjects

Sayyed Mehrab Ramezani

Publications and source records attributed to Sayyed Mehrab Ramezani.

5 recordsLinked to original sources
arXiv2026

Static Magnetic Brane Solutions in Quartic Quasi-Topological Gravity with Power-Law Maxwell Nonlinear Electrodynamics

In this paper, we investigate static magnetic brane solutions in (n+1)-dimensional quartic quasi-topological gravity coupled to power-law Maxwell nonlinear electrodynamics. We derive the corresponding solutions and analyze their geometric and physical properties. We observe that the solutions are horizonless and free of curvature singularities in the physically accessible region, while the spacetime generally exhibits a conical singularity with a nonzero angular deficit at the lower radial endpoint. We demonstrate that the endpoint is independent of the higher-curvature couplings lambda, mu, and c, whereas the near-endpoint geometry is mainly controlled by the magnetic parameter q and the nonlinear parameter s. At large radial distances, we find that the higher-curvature couplings govern the asymptotic behavior of the metric. We also establish that finite asymptotic solutions require 1/2 < s <= 2 and analyze the dependence of the angular deficit on q, s, and the endpoint parameter rho_+. Using the counterterm method, we calculate the conserved mass density and show that the static magnetic brane carries no net electric charge. Finally, we verify that the power-law Maxwell theory recovers linear Maxwell electrodynamics at s=1 and Einstein gravity when lambda=mu=c=0.

gr-qc↗
arXiv2026

Joule Thomson expansion of symmergent black holes in extended phase space

We investigate the Joule Thomson expansion of a symmergent black hole within an extended phase-space formalism in which the thermodynamic pressure is introduced as an independent variable. The symmergent entropy contains the parameter alpha-hat, which modifies the enthalpy and thermodynamic volume relative to their standard forms. We show that the Joule Thomson coefficient depends only on the combination 8piP*r_+^2, leading to an inversion curve P_i = (pi/2) * I_i^2 that is independent of alpha-hat. The isenthalpic curves, however, retain a parametric dependence on alpha-hat, indicating that the symmergent sector affects the thermodynamic trajectories but not the inversion boundary itself. The inversion pressure and temperature are derived explicitly, and the cooling regime P > P_i is distinguished from the heating regime P < P_i. Since the effective geometry is asymptotically AdS-like for positive pressure, the results also admit a holographic reading, in which the Joule Thomson expansion corresponds to an isenthalpic process in the dual field theory. The results provide a consistent thermodynamic framework for symmergent black holes and clarify the role of the symmergent parameters in the Joule Thomson process.

gr-qc↗
arXiv2026

Quantum-corrected thermodynamics of Schwarzschild AdS black holes in conformal Killing gravity

We study Schwarzschild--AdS black holes in conformal Killing gravity with non-perturbative entropy corrections within the extended phase-space formalism. By deriving the quantum-corrected heat capacity, Helmholtz free energy, internal energy, and Gibbs free energy, we show that quantum corrections modify phase transition points and thermal stability mainly at small horizon radii, while classical behavior is recovered for large black holes. Critical behavior of van der Waals type appears exclusively for positive values of the conformal Killing parameter $a$. Applying the island prescription, we find that the entanglement entropy of Hawking radiation saturates after the Page time at $S_{\text{sat}} = 2(πr_H^2 + ηe^{-πr_H^2})$, thereby restoring unitarity. Stronger quantum corrections increase the entropy threshold and delay information recovery. Furthermore, we examine the universal thermodynamic relation in the extremal limit under a minimal perturbation of the AdS curvature radius. We prove that the quantum correction parameter $η$ cancels out completely, yielding the robust universal combination $U = -r_{\text{ext}}^3 / l^3$. This demonstrates that the universal relation remains stable against non-perturbative quantum corrections to the entropy.

gr-qc↗
arXiv2024

Soft g-frames in soft Hilbert spaces

In this paper, we define the concept of soft $g$-frame in soft Hilbert spaces by extending the concept of soft from frame to $g$-frame. We then show some properties of the soft $g$-frames in soft Hilbert spaces. Among other results, we show that the $g$-frame operator is associated with a soft, finite, self-adjoining, reversible, and finite inverse $g$-frame and get the dual g-frames. In addition, we prove that every element in Hilbert's soft space satisfies the theorem of $g$-frame decomposition.

math.FA↗