Pseudo-Bounces vs. New Instantons

TL;DR

This paper compares pseudo-bounces and new instantons as decay configurations in false vacua where traditional bounces are absent, finding pseudo-bounces generally have lower action and better represent the decay process.

Contribution

It demonstrates that pseudo-bounces are more accurate and can produce significantly lower decay actions than new instantons in certain false vacuum decay scenarios.

Findings

Pseudo-bounces have lower action than new instantons.

Pseudo-bounces cover a wider field space range.

Pseudo-bounces can yield decay actions orders of magnitude lower.

Abstract

Some false vacua do not decay via bounces. This usually happens when a flat direction of the tunneling action due to scale invariance is lifted to a sloping valley by a scale breaking perturbation, pushing the bounce off to infinity. We compare two types of alternative decay configurations that have been proposed recently to describe decay in such cases: pseudo-bounces and new instantons. Although both field configurations are quite similar, we find that the pseudo-bounce action is lower than the new instanton one and describes more faithfully the bottom of the action valley. In addition, pseudo-bounces cover a range of field space wider than new instantons and, as a result, lead to an action that can be lower than the one for new instantons by orders of magnitude.