Study of entropy production due to electroweak phase transition in $Z_2$ symmetric extension of the Standard Model

TL;DR

This paper investigates how adding a real scalar in a Z2 symmetric extension of the Standard Model transforms the electroweak phase transition from a smooth crossover to a strong first order transition, affecting entropy and early universe conditions.

Contribution

It demonstrates that the Z2 symmetric extension induces a strong first order electroweak phase transition and increases entropy release compared to the Standard Model.

Findings

Transition changes from crossover to first order

Entropy release is higher than in SM

Potential dilution of dark matter and baryon asymmetry

Abstract

In this work we consider the simple $Z_2$ symmetric extension to the Standard Model (SM) and proceed to study the nature of electroweak phase transition (EWPT) in the early universe. We show that the nature of the phase transition changes from a smooth crossover in the SM to a strong first order with this addition of the real scalar. Furthermore, we show the entropy release in this scenario is higher than that of the SM. This can lead to a strong dilution of frozen out dark matter particles and baryon asymmetry, if something existed before the onset of the phase transition.