PQ-ball and its Real Scalar Analogue in an Expanding Universe

TL;DR

This paper uses lattice simulations to show how PQ-balls and oscillons form and decay in scalar field theories within an expanding universe, highlighting mechanisms relevant to Peccei-Quinn models.

Contribution

It introduces the formation and decay dynamics of PQ-balls and oscillons in scalar field theories through detailed numerical simulations.

Findings

PQ-balls form via coherent rotation of scalar fields.

PQ-balls decay due to U(1)-breaking effects.

Oscillons also form and decay in similar setups.

Abstract

We demonstrate the formation of quasi-stable localized scalar configurations in spontaneously symmetry breaking U(1) model by 3+1-dimensional classical lattice simulations. Such configurations are called PQ-balls, as the primary motivation of this kind of configuration is Peccei-Quinn theory under the kinetic misalignment mechanism. Our numerical simulations demonstrate that they can form if the PQ charge is generated through the coherent rotation of a complex scalar field in the complex plane, via dynamics analogous to the Affleck-Dine mechanism. These configurations subsequently decay due to the U(1)-breaking effect induced by spontaneous symmetry breaking. We also demonstrate the formation and decay of oscillons in a similar setup in a real scalar field theory.