arXiv subjects

Ammar Kasem

Publications and source records attributed to Ammar Kasem.

4 recordsLinked to original sources

arXiv2026

Classical diamagnetism at large magnetic fields

Many textbooks discuss the diamagnetic response of a ``classical atom'' to a small, adiabatically slowly applied magnetic field. Here we solve this problem for an arbitrarily large field. This gives a more satisfying justification for the assumptions made in the small field regime, explains the role of adiabaticity, identifies the symmetries persisting at large fields, and illustrates the range of applicability of the Larmor's theorem.

physics.ed-ph↗

arXiv2023

Primordial Gravitational Waves in Generalized Palatini Gravity

Extended Palatini gravity is the metric-affine gravity theory characterized by zero torsion, nonzero metricity and a quadratic of the antisymmetric Ricci curvature. It reduces dynamically to general relativity plus a geometric Proca field. In this work, we study imprints of the geometric Proca field in the gravitational waves . Our results show that the geometric Proca leaves significant signatures in the gravitational wave signal, and gravitational wave energy density is large enough to be detectable by the next upgrade of the existing GW detectors. Our results, if confirmed observationally, will be an indication that the gravity could well non-Riemannian in nature.

gr-qc↗

arXiv2020

Quantum Cosmology with vector torsion

We extend the treatment of quantum cosmology to a manifold with torsion. We adopt a model of Einstein-Cartan-Sciama-Kibble compatible with the cosmological principle. The universe wavefunction will be subject to a $\mathcal{PT}$-symmetric Hamiltonian. With a vanishing energy-momentum tensor, the universe evolution in the semiclassical and classical regimes is shown to reflect a two-stage inflationary process induced by torsion.

gr-qc↗

arXiv2020

Gauge-Field-Induced Torsion and Cosmic Inflation

Inflation in the framework of Einstein-Cartan theory is revisited. Einstein-Cartan theory is a natural extension of the General Relativity, with non-vanishing torsion. The connection on Riemann-Cartan spacetime is only compatible with the cosmological principal for a particular form of torsion. We show this form to also be compatible with gauge invariance principle for a non-Abelian and Abelian gauge fields under a certain deviced minimal coupling procedure. We adopt an Abelian gauge field in the form of "cosmic triad". The dynamical field equations are obtained and shown to sustain cosmic inflation with a large number of e-folds. We emphasize that at the end of inflation, torsion vanishes and the theory of Einstein-Cartan reduces to the General Relativity with the usual FRW geometry.

hep-th↗