Misalignment vs Topology in Axion-Like Models

TL;DR

This paper investigates how the timing of explicit symmetry breaking affects axion-like particle production in cosmology, emphasizing the role of topology and symmetry-breaking dynamics in dark matter formation.

Contribution

It introduces a study of axion-like models with explicit O(N) symmetry breaking, analyzing the impact of the symmetry-breaking onset speed on particle production efficiency.

Findings

Production efficiency is sensitive to how quickly the explicit O(N)-breaking potential is activated.

Topological structures influence the coherence and abundance of produced axion-like particles.

The timing of symmetry breaking significantly affects dark matter candidate viability.

Abstract

Cosmological axions, an important dark matter candidate, are generated when a scalar field with a spontaneously broken O(2) invariance develops an explicitly O(2)-breaking tilt cosmologically, leading to coherent production of long-wavelength modes which could be dark matter. It appears that the production efficiency of this mechanism is low, despite possible production from topological structures. To understand this better, we examine production in O(N) generalizations. In particular we highlight the importance of how fast the explicit O(N)-breaking potential turns on.