Date of Award

Fall 2025

Document Type

Open Access Dissertation

Department

Physics and Astronomy

First Advisor

Brett Altschul

Abstract

This dissertation presents a study of gravitational perturbations and quantum field dynamics in modified spacetime backgrounds. The research is motivated by the quest to understand how quantum fields behave in curved spacetimes, particularly when extensions to general relativity, such as Chern--Simons modifications, are introduced.

The first part examines quantum field interactions with oscillating solitonic backgrounds, inspired by breather-type solutions of the sine--Gordon equation. Fermion bound states are shown to undergo destabilization due to the oscillatory background, leading to particle production and flux propagation to infinity. These results highlight the challenges of maintaining localized fermionic states in time-dependent topological backgrounds.

The second part investigates axial perturbations of charged Reissner--Nordström black holes in Chern--Simons gravity. Analytical and numerical methods are employed to explore the behavior of the radial perturbation function under varying charge-to-mass ratios and angular momentum parameters. Resonance-like behavior, suppression of perturbations, and symmetrization in the extremal limit are identified, providing new insights into black hole stability in modified gravity theories.

The final part of this work focuses on perturbative analyses of the de Sitter metric, where gravitational waves in the transverse--traceless gauge are studied in the presence of Chern--Simons terms. The Pontryagin constraint is derived and shown to vanish at linear order, clarifying the role of parity-violating corrections in cosmological backgrounds.

Together, these studies shed light on the interplay between gravitational perturbations, quantum fields, and modifications to general relativity. They contribute to a deeper understanding of quantum field theory in curved spacetimes, with implications for black hole physics, cosmology, and solitonic field dynamics.

Rights

© 2025, Abhishek Rout

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