Hydrodynamic Stability Analysis of Burning Bubbles in Electroweak Theory and in QCD

TL;DR

The paper analyzes the hydrodynamic stability of burning phase-transition bubbles in the electroweak and QCD contexts, using a fully relativistic 1+1D deflagration/detonation framework and careful boundary conditions. It introduces a temperature-sensitivity parameter eta that governs stability and demonstrates that electroweak walls are stable for cosmologically relevant wall speeds, while QCD walls are borderline depending on latent heat and supercooling. The results challenge prior claims that subsonic walls are unstable and highlight the importance of boundary conditions and microphysics in wall dynamics. The findings have implications for electroweak baryogenesis scenarios and the cosmological role of the QCD phase transition.

Abstract

Assuming that the electroweak and QCD phase transitions are first order, upon supercooling, bubbles of the new phase appear. These bubbles grow to macroscopic sizes compared to the natural scales associated with the Compton wavelengths of particle excitations. They propagate by burning the old phase into the new phase at the surface of the bubble. We study the hydrodynamic stability of the burning and find that for the velocities of interest for cosmology in the electroweak phase transition, the shape of the bubble wall is stable under hydrodynamic perturbations. Bubbles formed in the cosmological QCD phase transition are found to be a borderline case between stability and instability.