Quantum Decay of Domain Walls In Cosmology I: Instanton Approach

TL;DR

This paper introduces a quantum decay process for large, closed domain walls in cosmology, using an instanton approach to calculate tunneling barriers and exploring their classical origins in the early universe.

Contribution

It presents a novel quantum decay mechanism for domain walls via instanton calculations and discusses their classical formation and evolution in cosmological settings.

Findings

Calculated the barrier factor for quantum tunneling of domain walls.

Proposed a new decay process involving vacuum fluctuations and wall collision.

Discussed the classical origin of large domain walls in the early universe.

Abstract

This paper studies the decay of a large, closed domain wall in a closed universe. Such walls can form in the presence of a broken, discrete symmetry. We introduce a novel process of quantum decay for such a wall, in which the vacuum fluctuates from one discrete state to another throughout one half of the universe, so that the wall decays into pure field energy. Equivalently, the fluctuation can be thought of as the nucleation of a second domain wall of zero size, followed by its growth by quantum tunnelling and its collision with the first wall, annihilating both. The barrier factor for this quantum tunneling is calculated by guessing and verifying a Euclidean instanton for the two-wall system. We also discuss the classical origin and evolution of closed, topologically spherical domain walls in the early universe, through a "budding-off" process involving closed domain walls larger than the Hubble radius. This paper is the first of a series on this subject.