Cosmological Consequences of Slow-Moving Bubbles in First-Order Phase Transitions

TL;DR

This study investigates the evolution and collision of slow-moving bubbles during cosmological first-order phase transitions, revealing that slow velocities suppress defect formation and influence primordial magnetic fields.

Contribution

It provides new insights into the dynamics of slow-moving bubbles, showing phase oscillations do not occur and defect formation is suppressed, which differs from previous models with faster bubbles.

Findings

Phase oscillations are absent in slow-moving local-symmetry bubbles.

Almost instantaneous phase equilibration reduces defect density.

Slow-moving walls may enhance primordial magnetic fields.

Abstract

In cosmological first-order phase transitions, the progress of true-vacuum bubbles is expected to be significantly retarded by the interaction between the bubble wall and the hot plasma. We examine the evolution and collision of slow-moving true-vacuum bubbles. Our lattice simulations indicate that phase oscillations, predicted and observed in systems with a local symmetry and with a global symmetry where the bubbles move at speeds less than the speed of light, do not occur inside collisions of slow-moving local-symmetry bubbles. We observe almost instantaneous phase equilibration which would lead to a decrease in the expected initial defect density, or possibly prevent defects from forming at all. We illustrate our findings with an example of defect formation suppressed in slow-moving bubbles. Slow-moving bubble walls also prevent the formation of `extra defects', and in the presence of plasma conductivity may lead to an increase in the magnitude of any primordial magnetic field formed.