Barnacles -- A Novel Channel for Vacuum Decay

TL;DR

This paper introduces 'barnacles' as a new, more frequent mechanism for vacuum decay in cosmology, which has similar observational effects as bubble collisions but occurs exponentially more often.

Contribution

It presents the concept of barnacles as a novel instability in cosmological bubble walls, expanding the understanding of vacuum decay processes.

Findings

Barnacles are loci of different wall tension adjacent to third vacuum regions.

Barnacle formation occurs exponentially more often than bubble collisions.

The process is described by a saddle point with two negative modes.

Abstract

I show that cosmological bubble walls in the thin wall approximation are unstable to the creation of "barnacles" -- loci of different wall tension adjacent to regions filled with a third vacuum. Barnacle formation leads to the same observational consequences as the extensively studied bubble collision scenario, but occurs exponentially more often. The process is described by a saddle point of the thin wall action with two negative modes.