What are universal features of gravitating Q-balls?

TL;DR

This paper explores the influence of gravity on Q-balls, revealing that stable, arbitrarily small charge Q-balls can exist under gravity, a phenomenon absent in flat spacetime, and identifies universal features of such gravitating Q-balls.

Contribution

It demonstrates that gravity enables stable small-charge Q-balls across a broad class of models, extending understanding of solitonic objects in gravitational fields.

Findings

Stable Q-balls with arbitrarily small charge exist under gravity.

This feature is universal for models with a positive mass term in the potential.

Gravity fundamentally alters the stability properties of Q-balls.

Abstract

We investigate how gravity affects Q-balls by exemplifying the case of the Affleck-Dine potential $V(\phi):=m^4 \ln (1+\frac{\phi^2}{m^2})$. Surprisingly, stable Q-balls with arbitrarily small charge exist, no matter how weak gravity is, contrary to the case of flat spacetime. We also show analytically that this feature holds true for general models as long as the leading order term of the potential is a positive mass term in its Maclaurin series.