Spinodal instability in an expanding universe

Abstract

We study the dynamics of matter undergoing a first order phase transition in an expanding universe. We contemplate the scenario where the universe experiences significant supercooling, leading to local instability known as spinodal instability. We use second-order hydrodynamics to derive the equation that governs the behavior of the unstable modes that arise in this situation, and numerically solve it. The resulting solutions differ significantly from the ones found for a flat universe. Specifically, we observe a damped behaviour and a notable time dependence in the momentum range of the unstable modes, highlighting the richer dynamics at play. Finally, we model this time dependence using an adiabatic approximation and show that it captures the main momentum and expansion rate dependence of unstable modes growth