The fate of small classically stable Q-balls

TL;DR

This paper develops a semiclassical method to calculate the quantum decay rate of metastable small Q-balls, revealing their instability and potential cosmological impacts.

Contribution

It introduces a general semiclassical approach using Euclidean solutions to determine Q-ball decay rates across all metastable regimes.

Findings

Derived a universal semiclassical decay rate formula for Q-balls.

Numerically computed decay rates in a specific one-field model.

Discussed potential cosmological consequences of metastable Q-balls.

Abstract

The smallest classically stable Q-balls are, in fact, generically metastable: in quantum theory they decay into free particles via collective tunneling. We derive general semiclassical method to calculate the rate of this process in the entire kinematical region of Q-ball metastability. Our method uses Euclidean field-theoretical solutions resembling the Coleman's bounce and fluctuations around them. As an application of the method, we numerically compute the decay rate to the leading semiclassical order in a particular one-field model. We shortly discuss cosmological implications of metastable Q-balls.