First-order phase transition and fate of false vacuum remnants

TL;DR

This paper investigates the formation and evolution of false vacuum remnants during first-order phase transitions in the early Universe, revealing their potential to become various dark matter candidates like primordial black holes, Fermi-balls, Q-balls, or thermal balls.

Contribution

It introduces a comprehensive analysis of the fate of false vacuum remnants in models with trapped dark sector particles, highlighting a new dark matter candidate called thermal balls.

Findings

Remnants can evolve into primordial black holes, Fermi-balls, Q-balls, or thermal balls.

Thermal balls can stay hot until today, serving as a novel dark matter candidate.

The fate depends on specific model and phase transition parameters.

Abstract

False vacuum remnants in first-order phase transitions in the early Universe can form compact objects which may constitute dark matter. Such remnants form because particles develop large mass gaps between the two phases and become trapped in the old phase. We focus on remnants generated in a class of models with trapped dark sector particles, trace their development, and determine their ultimate fate. Depending on model and phase transition parameters, the evolutionary endpoint of these remnants can be primordial black holes, Fermi-balls, Q-balls, or thermal balls, and they all have the potential to constitute some portion or the whole of dark matter within a broad mass range. Notably, dark sector thermal balls can remain at high temperatures until the present day and are a new compact dark matter candidate which derives its energy from the thermal energy of internal particles instead of their mass or quantum pressure.