arXiv subjects

Mohammed Zakarya

Publications and source records attributed to Mohammed Zakarya.

4 recordsLinked to original sources

arXiv2026

Study of Dynamical Instability of Collapsing Charged Spherically Symmetric Anisotropic Matter Configurations within Non-Minimally Coupled Gravity

We investigate the dynamical instability and gravitational collapse of charged, spherically symmetric anisotropic matter configurations within $f(R,\mathcal{L}_{m})$ gravity. The analysis focuses on the combined effects of anisotropic pressure, perturbations, electric charge, and modified-gravity source terms on the stability of compact objects. A specific equation of state is adopted to relate the static and perturbed variables through the adiabatic index. Using a perturbation scheme, we derive the modified hydrostatic equilibrium and collapse equations and obtain instability constraints in both Newtonian and post-Newtonian regimes. The results show that the stability of the system is governed by the competition between inward gravitational attraction and outward pressure support. In addition, the dark source terms generated by the non-minimal matter-geometry coupling modify the collapse conditions and can enhance the stability of the charged fluid. These findings provide a useful framework for understanding the evolution and collapse of dense self-gravitating compact objects in non-minimally coupled gravity.

gr-qc↗

arXiv2026

Beyond Classical Instability Limits of Anisotropic Self-gravitating Fluid Configurations in Hu-Sawicki Inspired f(R) Gravity

In this draft, we investigate the dynamical instability of a restricted class of non-static, axially symmetric, self-gravitating fluid configurations within a Hu-Sawicki inspired f(R) gravity model. The matter source is described by an anisotropic energy-momentum tensor containing three principal stresses and an off-diagonal stress component. For the adopted vorticity free geometry, conservation equations are formulated, and a linear perturbation scheme is applied to separate the equilibrium and time-dependent sectors. This procedure yields a collapse equation that governs the evolution of the perturbed compact configuration. The associated instability conditions are then derived in terms of the adiabatic index Γ under the Newtonian and post-Newtonian approximations, whereas the resulting bounds show that the onset of instability depends not only on the stiffness of the fluid, but also on the background energy density, directional pressure anisotropies, metric perturbations, and higher-curvature contributions generated by the Hu-Sawicki model. The general relativistic limit is recovered by suppressing the modified gravity parameters, while the isotropic limit reproduces the classical Chandrasekhar threshold. These results demonstrate that curvature corrections and anisotropic stresses can appreciably modify the conventional instability conditions of axially symmetric compact systems.

gr-qc↗

arXiv2026

Quantum thermodynamics, quantum correlations and quantum coherence in accelerating Unruh-DeWitt detectors in both steady and dynamical state

We investigate the interplay between quantum thermodynamics, quantum correlations, and quantum coherence within the framework of the Unruh-DeWitt (UdW) detector model. By analyzing both the steady and dynamical states of various quantum resources (including steerability, entanglement, quantum discord, and coherence), we study how these resources evolve under Markovian and non-Markovian environments. Furthermore, we investigate the impact of both the Unruh temperature and the energy levels on three key quantum phenomena: thermodynamic evolution, quantum correlations, and quantum coherence, considering different initial state preparations. The hierarchical structure relating quantum correlations and quantum coherence is determined. We further examine the thermodynamic performance of a quantum heat engine, highlighting the influence of memory effects and classical correlations on heat exchange, work extraction, and efficiency. Our results reveal that non-Markovian dynamics can enhance the preservation of quantum correlations and improve the engine's efficiency compared to purely Markovian regime. These findings provide insights into the role of quantum correlations and quantum coherence in quantum thermodynamic processes and open avenues for optimizing quantum devices operating in relativistic or open-system settings.

quant-ph↗

arXiv2025

Barnett Effect-Induced Nonreciprocal Entanglement and Gaussian interferometric power in Magnomechanics with Optical Parametric Amplifier

Nonreciprocity is a powerful tool in quantum technologies. It allows signals to be sent in one direction but not the other. In this article, we propose a method for achieving non-reciprocal entanglement and Gaussian interferometric power (GIP) via the Barnett effect. The YIG is coupled to a microwave cavity that interacts with an optical parametric amplifier (OPA). Due to the Barnett effect, giant nonreciprocal entanglement can emerge. By fine-tuning the cavity detuning, the GIP can exhibits nonreciprocal behavior. All entanglements with ideal nonreciprocity can be achieved by tuning the photon frequency detuning, appropriately choosing the cavity-magnon coupling regime, the nonlinear gain, and the phase shift of the OPA. Interestingly, the amount of entanglement nonreciprocity and its resilience to thermal occupation are remarkably enhanced by increasing the gain of the OPA. This nonreciprocity can be significantly enhanced even at relatively high temperatures. Our research offers a pathway for the realization of nonreciprocal single-phonon devices, with potential applications in quantum information processing and quantum communication. This proposed scheme could pave the way for the development of novel nonreciprocal devices that remain robust under thermal fluctuations.

quant-ph↗