Baryon Washout, Electroweak Phase Transition, and Perturbation Theory

TL;DR

This paper critiques the gauge dependence of traditional perturbative methods in electroweak baryogenesis, proposing a gauge-independent criterion for baryon number preservation and discussing the necessary higher-order calculations.

Contribution

It introduces a gauge-independent criterion for baryon number preservation and highlights the need for complete two-loop and one-loop calculations in beyond Standard Model scenarios.

Findings

Conventional perturbation theory is gauge-dependent.

A gauge-independent criterion for baryon preservation is proposed.

Higher-order calculations are necessary for realistic scenarios.

Abstract

We analyze the conventional perturbative treatment of sphaleron-induced baryon number washout relevant for electroweak baryogenesis and show that it is not gauge-independent due to the failure of consistently implementing the Nielsen identities order-by-order in perturbation theory. We provide a gauge-independent criterion for baryon number preservation in place of the conventional (gauge-dependent) criterion needed for successful electroweak baryogenesis. We also review the arguments leading to the preservation criterion and analyze several sources of theoretical uncertainties in obtaining a numerical bound. In various beyond the standard model scenarios, a realistic perturbative treatment will likely require knowledge of the complete two-loop finite temperature effective potential and the one-loop sphaleron rate.