arXiv subjects

Hassan Alshal

Publications and source records attributed to Hassan Alshal.

14 recordsLinked to original sources

arXiv2025

Spin-2 fields, Lee-Wick Ghosts, and GUP

We revisit the structure of higher-derivative spin-2 theories from the perspective of the Generalized Uncertainty Principle (GUP). We show that a minimal GUP deformation of the Fierz-Pauli (FP) action induces a higher-derivative kinetic operator equivalent, at quadratic order, to the spin-2 sector of Stelle's curvature-squared gravity. Via an auxiliary-field formulation, the GUP-generated higher derivative can be recast as a Lee-Wick (LW) partner of the spin-2. We then demonstrate that the same GUP deformation is compatible with the Galileon structure governing the helicity-0 mode in dRGT massive gravity. The GUP corrections reduce to total derivatives, preserving the absence of the Boulware-Deser ghost. Our results unify GUP models, LW quantization, and curvature-squared gravity into a single framework, in which the higher-derivative spin-2 ghost is rendered non-propagating while the nonlinear massive completion remains intact.

gr-qc↗

arXiv2024

Linearized Stability of Harada Thin-Shell Wormholes

Using Darmois-Israel-Sen junction conditions, and with help of Visser's cut-and-paste method, we study the dynamics of thin-shell wormholes that are made of two conformally Killing gravity (a.k.a Harada gravity) black holes. We check the energy conditions for different values of the new parameter that Harada introduced, as alternative for dark energy. We examine the radial acceleration to reveal the attractive and repulsive characteristics of the thin-shell wormhole throat. We consider the dynamics and stability of the wormhole around the static solutions of the linearized radial perturbations at the wormhole throat. Finally, we determine the regions of stability by applying the concavity test on the ``speed of sound'' as a function in the throat radius and other spacetime parameters, particularly the new Harada parameter.

gr-qc↗

arXiv2024

Gravitational Observations and LQGUP

Motivated by recent works, we employ the bounds on the dimensionless quantum-gravity parameter obtained from six gravitational tests in order to obtain bounds on the dimensionless parameter of the generalized uncertainty principle with linear and quadratic terms in momentum. The bounds obtained here are much tighter than those obtained, from the same six gravitational tests, for the dimensionless parameter of the uncertainty principle with only quadratic terms in momentum.

gr-qc↗

arXiv2023

Einstein's equations and the pseudo-entropy of pseudo-Riemannian information manifolds

Motivated by the corrected form of the entropy-area law, and with the help of von Neumann entropy of quantum matter, we construct an emergent spacetime by the virtue of the geometric language of statistical information manifolds. We discuss the link between Wald and Jacobson approaches of thermodynamic/gravity correspondence and Fisher pseudo-Riemannian metric of information manifold. We derive in detail Einstein's field equations in statistical information geometric forms. This results in finding a quantum origin of a positive cosmological constant that is founded on Fisher metric. This cosmological constant resembles those found in Lovelock's theories in a de Sitter background as a result of using the complex extension of spacetime and the Gaussian exponential families of probability distributions, and we find a time varying dynamical gravitational constant as a function of Fisher metric together with the corresponding Ryu-Takayanagi formula of such system. Consequently, we obtain a dynamical equation for the entropy in information manifold using Liouville-von Neumann equation from the Hamiltonian of the system. This Hamiltonian is suggested to be non-Hermitian, which corroborates the approaches that relate non-unitary conformal field theories to information manifolds. This provides some insights on resolving "the problem of time".

gr-qc↗

arXiv2022

Unitary symmetries in wormhole geometry and its thermodynamics

From a geometric point of view, we show that the unitary symmetries $U(1)$ and $SU(2)$ stem fundamentally from Schwarzschild and Reissner-Nordström wormhole geometry through spacetime complexification. Then, we develop quantum tunneling which makes these wormholes traversable for particles. Finally, this leads to wormhole thermodynamics.

hep-th↗

arXiv2021

Dual Fields of Massive/Massless Gravitons in IR/UV Completions

In the holographic picture, the Brout-Englert-Higgs (BEH) mechanism in d-dimensional Yang-Mills theories is conjectured to provide a Higgs-like mechanism for gravity in d+1 dimensions, resulting in massive (or massless) gravitons in IR (or UV) completions. Accordingly, one could imagine dual (magnetic-type) fields of massive gravitons in the IR (low-energy) limit that are coupled to the curl of their own energy-momentum, as well as to the rotation of matter fields on large scales. This hypothesis, which might solve cosmological issues currently ascribed to dark matter and dark energy, needs to be examined by the future Laser Interferometer Space Antenna (LISA) mission using observations of gravitational waves emitted from extragalactic sources.

hep-th↗

arXiv2021

Massless Charged Particles Tunneling Radiation from a RN-dS Horizon and the Linear and Quadratic GUP

In this paper, we investigate the massless Reissner-Nordstrom de Sitter metric in the context of minimal length scenarios. We prove not only the confinement of the energy density of massless charged particles, both fermions and bosons, but also their ability to tunnel through the cosmological horizon. These massless particles might be interacting with Dirac sea and in this case they will appear outside the cosmological horizon in the context of dS/CFT holography. This result may formulate a fundamental reason for the expansion of the Dirac sea. Therefore, a spacetime Big Crunch may occur.

hep-th↗

arXiv2020

A Galileon Primer

Elementary features of galileon models are discussed at an introductory level. Following a simple example, a general formalism leading to a hierarchy of field equations and Lagrangians is developed for flat spacetimes. Legendre duality is discussed. Implicit and explicit solutions are then constructed and analyzed in some detail. Galileon shock fronts are conjectured to exist. Finally, some interesting general relativistic effects are studied for galileons coupled minimally to gravity. Spherically symmetric galileon and metric solutions with naked curvature singularities are obtained and are shown to be separated from solutions which exhibit event horizons by a critical curve in the space of boundary data.

hep-th↗

arXiv2020

Linearized Stability of Bardeen de-Sitter Thin-Shell Wormholes

A thin-shell wormhole is crafted by the cut-and-paste method of two Bardeen de-Sitter black holes using Darmois-Israel formalism. Energy conditions are considered for different values of magnetic charge while both mass and cosmological constant are fixed. The attractive and repulsive characteristics of the throat of the thin-shell wormhole are also examined through the radial acceleration. Dynamics and stability of the wormhole are studied around the static solutions of the linearized radial perturbations at the throat of the wormhole. The regions of stability are determined by checking out the condition of concavity of the potential as a function in the throat radius for different values of magnetic charges.

gr-qc↗

arXiv2019

Proton Decay and the Quantum Structure of Spacetime

Virtual black holes in noncommutative spacetime are investigated using coordinate coherent state formalism such that the event horizon of black hole is manipulated by smearing it with a Gaussian of width $ \sqrt θ$, where $ θ$ is the noncommutativity parameter. Proton lifetime, the main associated phenomenology of the noncommutative virtual black holes, has been studied: first in $4$ dimensional spacetime and then generalized to $D$ dimensions. The lifetime depends on $ θ$ and the number of spacetime dimensions such that it emphasizes on the measurement of proton lifetime as a potential probe for the micro-structure of spacetime.

hep-th↗

arXiv2019

Linear and Quadratic GUP, Liouville Theorem, Cosmological Constant, and Brick Wall Entropy

Motivated by the works on Equivalence Principle in the context of linear Generalized Uncertainty Principle and, independently, in the context of quadratic Generalized Uncertainty Principle, we expand these endeavors in the context of Generalized Uncertainty Principle when both linear and quadratic terms in momentum are include. We demonstrate how the definitions of equations of motion change upon that expansion. We also show how to obtain an analogue of Liouville theorem in the presence of linear and quadratic Generalized Uncertainty Principle. We employ the corresponding modified invariant unit volume of phase space to discuss the resulting density of states, the problem of cosmological constant, the black body radiation in curved spacetime, the concurrent energy and consequent no Brick Wall entropy.

hep-th↗

arXiv2019

Green Functions, Sommerfeld Images, and Wormholes

Electrostatic Green functions for grounded equipotential circular and elliptical rings, and grounded hyperspheres in n-dimension electrostatics, are constructed using Sommerfeld's method. These electrostatic systems are treated geometrically as different radial p-norm wormhole metrics that are deformed to be the Manhattan norm, namely "squashed wormholes". Differential geometry techniques are discussed to show how Riemannian geometry plays a rule in Sommerfeld's method. A comparison is made in terms of strength and position of the image charges for Sommerfeld's method with those for the more conventional Kelvin's method. Both methods are shown to be mathematically equivalent in terms of the corresponding Green functions. However, the two methods provide different physics perspectives, especially when studying different limits of those electrostatic systems. Further studies of ellipsoidal cases are suggested.

physics.class-ph↗

arXiv2019

Massless Charged Particles, Naked Singularity, and Generalized Uncertainty Principle in Reissner-Nordström-de Sitter-like spacetime

Motivated by the endeavors of Li Xiang and You-Gen Shen on naked singularities, we investigate the validity of the cosmic censorship conjecture in the context of generalized uncertainty principle. In particular, upon considering both linear and quadratic terms of momentum in the uncertainty principle, we first compute the entropy of a massless charged black hole in de Sitter spacetime at a given modified temperature. Then, we compute the corresponding modified cosmological radius and express the black hole electric charge in terms of this modified cosmological radius and, thus, in terms of the generalized uncertainty principle parameter. Finally, we examine whether such a system will end up being a naked singularity or it might be protected by the cosmic censorship conjecture, and how that might be related to the possible existence of massless charged particles.

hep-th↗

arXiv2019

GUP and the no-cloning theorem

Motivated by a recent work by Yongwan Gim, Hwajin Um, and Wontae Kim, we investigate the validity of the no-cloning theorem in the context of generalized uncertainty principle. In particular, in the presence of linear and quadratic terms of momentum in generalized uncertainty principle, we first compute the energy density at a given modified temperature and then using the modified Stefan-Boltzmann law we derive the modified Page time. Finally, we calculate the modified required energy for the information to be encoded into a message and be sent to an observer inside the black hole.

gr-qc↗