arXiv subjects

Ar Rohim

Publications and source records attributed to Ar Rohim.

9 recordsLinked to original sources

arXiv2026

Renormalization group improved black holes in non-commutative momentum-dependent spacetime geometry

We investigate black holes (BHs) in momentum-dependent spacetime geometry and assess its quantum Reissner-Nordstr\"om (RN) consistency with the weak gravity conjecture (WGC). Quantum corrections are introduced through the non-commutative momentum space algebra as the quantization process, and spacetime renormalization approach as a map between momentum and spacetime spaces. For the Schwarzschild case, thermodynamic analysis indicates the existence of a hot (non-zero temperature) BH remnant when evaporation stops (the entropy becomes zero), obeying a complementary third law for black hole thermodynamics. We extend this framework to the RN solution and examine its extremal limit. For large BHs with $M \gg M_P$ ($M_P$ for Planck mass), the quantum-improved RN geometry exhibits a non-zero Hawking temperature in the extremal case, consistent with the WGC, which stipulates that extremal states should not be exactly stable or cold. The resulting momentum-dependent metric and thermodynamic properties are shown to reproduce the results derived from the Poincar\'e algebra (classical model) in the infrared (IR) regime.

gr-qc↗

arXiv2026

Thermal Casimir Effect in A Schwarzschild-like Wormhole Spacetime

We study the finite-temperature Casimir effect for a massless scalar field confined between two parallel plates in a Schwarzschild-like wormhole spacetime. Imposing Dirichlet boundary conditions, we compute the renormalized Casimir free energy in the comoving frame. We find that the thermal correction to the renormalized Casimir free energy decreases gradually with the temperature and becomes independent of the background geometry in this frame. Thermodynamic quantities derived from the Casimir free energy, namely, the renormalized Casimir entropy, internal energy, and heat capacity at constant volume, exhibit distinct temperature dependence. At low temperatures, all thermodynamic quantities recover the expected behavior, consistent with the fundamental laws of thermodynamics. These results provide a compact framework for analyzing quantum vacuum forces in gravitational backgrounds.

hep-th↗

arXiv2025

Fermionic Casimir effect in the presence of compact dimension in field theory with Lorentz invariance violation

In this study, we investigate the effect of the Lorentz invariance violation on the Casimir energy and pressure of the massive fermion field in the presence of the compact dimensions with topological $R^4\times S^1$, referring to the Kaluza-Klein model. In the system, the Dirac field is confined between two parallel plates with the geometry described by MIT bag boundary conditions, and the compactified dimension satisfies quasi-periodic boundary conditions. We investigate two directions of the Lorentz violation, namely, space- and time-like. The results reveal that in the space-like vector case, the Lorentz violation's strength and the extra dimension affect the Casimir energy and pressure. In contrast, in the time-like vector case, they are only affected by the extra dimension. We also propose an indirect method to estimate the size of the extra dimension by comparing the frequency shift of the massless fermionic case to that of the scaled experimental data for the electromagnetic field.

hep-th↗

arXiv2023

Violation of the two-time Leggett-Garg inequalities for a harmonic oscillator

We investigate the violation of the Leggett-Garg inequalities for a harmonic oscillator in various quantum states. We focus on the two-time quasi-probability distribution function with a dichotomic variable constructed with the position operator of a harmonic oscillator. First, we developed a new formula to compute the two-time quasi-probability distribution function, whose validity is demonstrated in comparison with the formula developed in the recent paper by Mawby and Halliwell[Phys.Rev.A, 107 032216 (2023)]. Second, we demonstrated the variety of the violation of the two-time Leggett-Garg inequalities assuming various quantum states of a harmonic oscillator including the squeezed coherent state and the thermal squeezed coherent state. Third, we demonstrated that a certain type of extension of the dichotomic variable and the corresponding projection operator can boost violation of the Leggett-Garg inequalities for the ground state and the squeezed state. We also discuss when the Leggett-Garg inequalities are violated in an intuitive manner.

quant-ph↗

arXiv2023

Casimir effect of Lorentz-violating charged Dirac in background magnetic field

We study the effect of the Lorentz symmetry breaking on the Casimir energy of charged Dirac in the presence of a uniform magnetic field. We use the boundary condition from the MIT bag model to represent the property of the plates. We investigate two cases of the direction of violation, namely, time-like and space-like vector cases. We discuss how the Lorentz violation and the magnetic field affect the structure of the Casimir energy and its pressure. We also investigate the weak and strong magnetic field cases with two different limits, heavy and light masses.

hep-th↗

arXiv2023

Massive fermion between two parallel chiral plates

We study the system of a massive fermion field confined between two parallel plates, where the properties of both plates are discussed under chiral MIT boundary conditions. We investigate the effects of the chiral angle on the Casimir energy for a massive fermion field with the general momentum. We find that the Casimir energy as a function of the chiral angle is generally symmetric, and the attractive Casimir force in the chiral case is stronger than that in the nonchiral case. In addition, we investigate the approximate Casimir energy for light and heavy mass cases. The behavior of the discrete momentum and changes of spin orientation are also discussed.

hep-th↗

arXiv2022

Effects of chiral MIT boundary conditions for a Dirac particle in a box

We investigate the effects of the chiral MIT boundary conditions for a Dirac particle in a 1D box. We show how the boundary condition affects the discrete momentum, energy level, transition frequency, and spin state in a box. The effects of the chiral MIT boundary conditions on the probability and scalar densities are also demonstrated. The results show that an asymmetric distribution appears in the box depending on the parameters of the spin orientation and chiral angle.

hep-ph↗

arXiv2022

Relativistic quantum bouncing particles in a homogeneous gravitational field

In this paper, we study the relativistic effect on the wave functions for a bouncing particle in a gravitational field. Motivated by the equivalence principle, we investigate the Klein-Gordon and Dirac equations in Rindler coordinates with the boundary conditions mimicking a uniformly accelerated mirror in Minkowski space. In the nonrelativistic limit, all these models in the comoving frame reduce to the familiar eigenvalue problem for the Schrödinger equation with a fixed floor in a linear gravitational potential, as expected. We find that the transition frequency between two energy levels of a bouncing Dirac particle is greater than the counterpart of a Klein-Gordon particle, while both are greater than their nonrelativistic limit. The different corrections to eigen-energies of particles of different nature are associated with the different behaviors of their wave functions around the mirror boundary.

gr-qc↗

arXiv2021

Entanglement of the Vacuum between Left, Right, Future, and Past: Dirac spinor in Rindler spaces and Kasner spaces

We study the relations of the positive frequency mode functions of Dirac field in 4-dimensional Minkowski spacetime covered with Rindler and Kasner coordinates, and describe the explicit form of the Minkowski vacuum state with the quantum states in Kasner and Rindler regions, and analytically continue the solutions. As a result, we obtain the correspondence of the positive frequency mode functions in Kasner region and Rindler region in a unified manner which derives vacuum entanglement.

gr-qc↗