arXiv subjects

Idrus Husin Belfaqih

Publications and source records attributed to Idrus Husin Belfaqih.

5 recordsLinked to original sources

arXiv2026

Black holes in effective loop quantum gravity: Hawking radiation

Emergent modified gravity provides a covariant framework for holonomy effects in models of loop quantum gravity with consistent black hole solutions coupled to a scalar field. Several independent studies of the Hawking thermal distribution are shown here to lead to the same final result. This internal consistency is a direct consequence of general covariance, which is analogous to the situation in classical general relativity but highly nontrivial in the context of modified canonical gravity. Holonomy corrections to the evaporation rate enter through the greybody factor, slowing down the evaporation process when the holonomy modification function decreases monotonically. Accounting for backreaction, corrected covariant semi-classical stress-energy tensors are computed in various vacuum states. Thanks to these results, the new concept of a net stress-energy tensor makes it possible to compute evaporation rates directly from energy conservation laws.

gr-qc↗

arXiv2025

Hawking evaporation and the fate of black holes in loop quantum gravity

A recent covariant formulation, that includes non-perturbative effects from loop quantum gravity (LQG) as self-consistent effective models, has revealed the possibility of non-singular black hole solutions. The new framework makes it possible to couple scalar matter to such LQG black holes and derive Hawking radiation in the presence of quantum space-time effects while respecting general covariance. Standard methods to derive particle production both within the geometric optics approximation and the Parikh-Wilczek tunneling approach are therefore available and confirm the thermal nature of Hawking radiation. The covariant description of scale-dependent decreasing holonomy corrections maintains Hawking temperature as well as universality of the low-energy transmission coefficients, stating that the absorption rates are proportional to the horizon area at leading order. Quantum-geometry effects enter the thermal distribution only through sub-leading corrections in the greybody factors. Nevertheless, they do impact energy emission of the black hole and its final state in a crucial way regarding one of the main questions of black-hole evaporation: whether a black-to-white-hole transition, or a stable remnant, is preferred. For the first time, a first-principles derivation, based on a discussion of backreaction, finds evidence that points to the former outcome.

gr-qc↗

arXiv2024

Lessons for loop quantum gravity from emergent modified gravity

Most of the potential physical effects of loop quantum gravity have been derived in effective models that modify the constraints of canonical general relativity in specific forms. Emergent modified gravity evaluates important conditions that ensure the existence of a compatible geometrical space-time interpretation of canonical solutions, as well as phase-space covariance under different choices of canonical variables. This setting, specialized to modifications suggested by loop quantum gravity, is therefore an important contribution to physical evaluations of this approach to quantum gravity. Here, it is shown that emergent modified gravity restricts several ambiguities that existed in previous formulations, rules out several specific candidates, and provides a unified treatment of different types of (holonomy) modifications that had been thought to be physically distinct.

gr-qc↗

arXiv2024

Black holes in effective loop quantum gravity: Covariant holonomy modifications

Emergent modified gravity provides a covariant, effective framework for obtaining spherically symmetric black hole solutions in models of loop quantum gravity with scale-dependent holonomy modifications. Exact solutions for vacuum black holes in the presence of a cosmological constant are derived here and analyzed in four different gauges, explicitly related to one another by standard coordinate transformations. The global structure is obtained by gluing space-time regions corresponding to the gauge choices, reconstructing a non-singular wormhole space-time for an arbitrary scale-dependent holonomy parameter. This outcome demonstrates the robustness of black-hole models with covariant holonomy modifications under quantization ambiguities. Compared with previous constructions, full covariance of the resulting space-time models as derived here implies subtle new effects and leads to a novel understanding of the parameters in holonomy modifications, distinguishing a constant holonomy length from a possibly scale-dependent function that may change coefficients of holonomy terms. New physical results are obtained for instance in the context of a non-trivial zero-mass limit of holonomy-modified space-times. The existence of a consistent effective space-time structure implies various novel aspects of a net gravitational stress-energy and related thermodynamical properties.

gr-qc↗

arXiv2021

White dwarfs and generalized uncertainty principle

This work is motivated by the sign problem in a logarithmic parameter of black hole entropy and the existing more massive white dwarfs than the Chandrasekhar mass limit. We examine the quadratic, linear, and linear-quadratic generalized uncertainty principle (GUP) models within the virtue of recent masses and radii of white dwarfs. We consider the modification generated by introducing the minimal length proposal on the degenerate Fermi gas equation of state (EOS) and on the hydrostatic equation. For the latter, we applied Verlinde's proposal regarding entropic gravity to derived the quantum corrected Newtonian gravity which in turn responsible for modifying the hydrostatic equation. Through the chi-square analysis of the models, we have found that the observation data favor the quadratic dan linear GUP models without mass limit. However, for the quadratic-linear GUP model, we can obtain the positive value of the free parameter $γ_0$ as well as we can get mass limit more massive than the Chandrasekhar mass limit. In the linear-quadratic GUP model, the formation of stable massive white dwarfs than the Chandrasekhar limit is possible only if both parameters are not equal.

gr-qc↗