Ensemble fermions for electroweak dynamics and the fermion preheating temperature

TL;DR

This paper refines ensemble fermion methods for electroweak simulations, demonstrating convergence with small ensemble sizes and calculating a lower bound on the preheating temperature, which impacts baryogenesis theories.

Contribution

It introduces an improved ensemble fermion implementation for electroweak dynamics and applies it to determine the preheating temperature relevant for baryogenesis.

Findings

Convergence of observables with small ensemble sizes.

Preheating temperature never below 20 GeV.

Standard Model CP-violation insufficient for baryogenesis.

Abstract

We refine the implementation of ensemble fermions for the electroweak sector of the Standard Model, introduced previously. We consider the behavior of different observables as the size of the ensemble is increased and show that the dynamics converges for ensemble sizes small enough that simulations of the entire electroweak sector become numerically tractable. We apply the method to the computation of the effective preheating temperature during a fast electroweak transition, relevant for Cold Electroweak Baryogenesis. We find that this temperature is never below 20 GeV, and this in combination with the early results convincingly rules out Standard Model CP-violation as the origin of the baryon asymmetry of the Universe.