arXiv subjects

Abhishek Rout

Publications and source records attributed to Abhishek Rout.

4 recordsLinked to original sources

arXiv2026

Gravitational Wave Parity-Violating Strain from Pulsar Glitches in Chern-Simons Modified Gravity

We investigate gravitational-wave birefringence from pulsar glitches in dynamical Chern-Simons gravity, a parity-violating extension of general relativity motivated by string theory and quantum gravity. Using the Hartle-Thorne slow-rotation formalism to model the neutron star background and a perturbative treatment of the Chern-Simons coupling $α$, we derive the modified Regge-Wheeler equation governing axial gravitational perturbations and compute the resulting polarization-dependent phase shift. The parity-violating interaction produces a fractional asymmetry between the right- and left-handed circular polarizations that scales as $α^2$, grows linearly with frequency and rotation rate, and falls as the fourth power of the stellar radius. For a constant-density interior model we obtain an analytic matching solution for the background scalar field, and show that the interior curvature factor vanishes identically--the interior solution being conformally flat--so that the scalar dipole is sourced entirely in the vacuum exterior; a centrally condensed equation of state can only increase the predicted signal. We further extend the analysis to a two-fluid model incorporating differential rotation between the neutron superfluid and the charged component; the resulting correction is bounded by the fractional glitch amplitude itself, independently of the equation of state, and is negligible for typical pulsar parameters. Expressed through the dimensionless quantity $ζ\propto αM/R_\star^{3}$, the fractional polarization asymmetry for millisecond pulsars reaches $\sim 10^{-3}$ at kilohertz frequencies at the boundary of perturbative validity--four orders of magnitude above the sensitivity of current ground-based detectors to strain asymmetries. However, realistic bounds are limited by the signal-to-noise ratio required to resolve a ratio of gravitational wave strains.

gr-qc↗

arXiv2026

First Order Axial Perturbation of the Reissner-Nordström Metric in a Possible Parity-Violating Gravity Background

We study axial perturbations of Reissner-Nordström black holes within the general framework of parity-violating modified gravity theories. We derive the governing equations for a class of frame-dragging perturbations, focusing on the symmetry structure and radial dependence of the perturbed metric component, describing its behavior across three distinct regions: near the singularity ($r \rightarrow 0$), between the inner and outer Reissner-Nordström horizons ($r_-< r< r_+$), and in the asymptotic exterior regime ($r \rightarrow \infty$). Using a combination of analytical and numerical methods, we analyze the solutions for varying black hole charge-to-mass ratios ($Q/M$) and angular momentum parameters ($l$). Key findings include the suppression of perturbations by the electromagnetic field for higher $Q/M$; the emergence of radial resonance-like behavior for specific $l$ values; and a high degree of symmetry for solutions in the extremal limit ($Q/M \sim 1$), attributed to the AdS$_2 \times S^2$ near-horizon geometry. The WKB approximation is employed to study the high-$l$ regime, revealing quantized radial resonance modes and singular behavior in the extremal limit. Additionally, we explore the role of boundary conditions and the possibility of a Chern-Simons field $Θ$ as the source of the parity violation, showing that consistency and the behavior of the perturbations under time reversal demand a constant field (and thus no actually observable Chern-Simons effects) at leading order. These results provide a basis for further analysis of the stability and dynamical properties of charged black holes in parity-violating theories, with potential experimental signatures in gravitational wave observations.

gr-qc↗

arXiv2025

Primordial Gravitational Wave Birefringence in a de Sitter Background with Chern-Simons Coupling

In this work, we investigate tensor perturbations in a de Sitter background within the framework of Chern-Simons modified gravity. We introduce transverse-traceless perturbations and analyze how the Chern-Simons Cotton tensor induces parity-violating modifications to gravitational wave propagation, while the Pontryagin density vanishes at linear order. Using a mode decomposition of the scalar background field, we derive the sub- and super-horizon limits of the wave equations and uncover chiral corrections in the dispersion relations of tensor modes. The resulting birefringence exhibits both amplitude and velocity components, alternating with the phase of the scalar field. Particular solutions sourced by the scalar background show helicity-dependent amplification and a characteristic scaling of the radiated flux that reduces smoothly to the Minkowski limit. The accumulated phase difference between right- and left-handed modes grows quadratically inside the horizon and becomes frozen outside, leaving a permanent parity-violating imprint in the primordial tensor spectrum. Finally, by promoting the Chern-Simons field to a massive dark matter candidate, we demonstrate how its mass-dependent dynamics connect gravitational birefringence to axion-like dark matter phenomenology.

gr-qc↗

arXiv2024

Bound States and Particle Production by Breather-Type Background Field Configurations

We investigate the interaction of fermion fields with oscillating domain walls, inspired by breather-type solutions of the sine-Gordon equation, a nonlinear system of fundamental importance. Our study focuses on the fermionic bound states and particle production induced by a time-dependent scalar background field. The fermions couple to two domain walls undergoing harmonic motion, and we explore the resulting dynamics of the fermionic wave functions. We demonstrate that while fermions initially form bound states around the domain walls, the energy provided by the oscillatory motion of the scalar field induces an outward flux of fermions and antifermions, leading to particle production and eventual flux propagation toward spatial infinity. Through numerical simulations, we observe that the fermion density exhibits quasiperiodic behavior, with partial recurrences of the bound state configurations after each oscillation period. However, the fermion wave functions do not remain localized, and over time, the density decreases as more particles escape the vicinity of the domain walls. Our results highlight that the sine-Gordon-like breather background, when coupled non-supersymmetrically to fermions, does not preserve integrability or stability, with the oscillations driving a continuous energy transfer into the fermionic modes. This study sheds light on the challenges of maintaining steady-state fermion solutions in time-dependent topological backgrounds and offers insights into particle production mechanisms in nonlinear dynamical systems with oscillating solitons.

hep-th↗