Solitons in generalized galileon theories

TL;DR

This paper investigates the existence and stability of solitons in generalized galileon theories, showing that potential terms and time dependence can allow stable static solitons and moving solitons under certain conditions.

Contribution

It extends previous no-go results by analyzing generalized galileons and demonstrates conditions under which stable static and moving solitons can exist.

Findings

Stable static solitons are not ruled out with potential terms.

Moving solitons at the speed of light can exist in certain galileon models.

Stability of these solitons depends on specific background conditions.

Abstract

We consider the existence and stability of solitons in generalized galileons, scalar field theories with higher-derivative interactions but second-order equations of motion. It has previously been proven that no stable, static solitons exist in a single galileon theory using an argument invoking the existence of zero modes for the perturbations. Here we analyze the applicability of this argument to generalized galileons and discuss how this may be avoided by having potential terms in the energy functional for the perturbations, or by including time dependence. Given the presence of potential terms in the Lagrangian for the perturbations, we find that stable, static solitons are not ruled out in conformal and (A)dS galileons. For the case of DBI and conformal galileons, we find that solitonic solutions moving at the speed of light exist, the former being stable and the latter unstable if the background soliton satisfies a certain condition.