Droplet collapse during strongly supercooled transitions

TL;DR

This paper investigates the decay of isolated droplets during cosmological phase transitions, comparing spherical simulations with multi-bubble results to understand their impact on gravitational wave signals and baryogenesis.

Contribution

It provides a detailed analysis of droplet decay in spherical symmetry and compares it with multi-bubble simulations, highlighting limitations for gravitational wave predictions.

Findings

Late-time wall velocities match 3D simulation results.

Spherical simulations poorly predict kinetic energy production.

Droplet formation affects baryogenesis but not gravitational wave suppression.

Abstract

We simulate the decay of isolated, spherically symmetric droplets in a cosmological phase transition. It has long been posited that such heated droplets of the metastable state could form, and they have recently been observed in 3D multi-bubble simulations. In those simulations, the droplets were associated with a reduction in the wall velocity and a decrease in the kinetic energy of the fluid, with a consequent suppression in the gravitational wave power spectrum. In the present work, we track the wall speed and kinetic energy production in isolated droplets and compare them to those found in multi-bubble collisions. The late-time wall velocities that we observe match those of the 3D simulations, though we find that the spherical simulations are a poor predictor of the kinetic energy production. This implies that spherically symmetric simulations could be used to refine baryogenesis predictions due to the formation of droplets, but not to estimate any accompanying suppression of the gravitational wave signal.