Cosmological phase transitions: is effective field theory just a toy?

TL;DR

This paper critically examines the use of effective field theory (EFT) in modeling first order cosmological phase transitions, showing it is generally inadequate except in specific Higgs-singlet scenarios, and discusses implications for dark sector transitions.

Contribution

The study demonstrates analytically and numerically that SM-EFT cannot reliably describe first order phase transitions in perturbative extensions of the Standard Model, except for certain Higgs-singlet cases.

Findings

SM-EFT fails to describe most first order phase transitions

Higgs-singlet extension with tree-level matching is an exception

Truncated dim-6 EFT provides only qualitative insights

Abstract

To obtain a first order phase transition requires large new physics corrections to the Standard Model (SM) Higgs potential. This implies that the scale of new physics is relatively low, raising the question whether an effective field theory (EFT) description can be used to analyse the phase transition in a (nearly) model-independent way. We show analytically and numerically that first order phase transitions in perturbative extensions of the SM cannot be described by the SM-EFT. The exception are Higgs-singlet extension with tree-level matching; but even in this case the SM-EFT can only capture part of the full parameter space, and if truncated at dim-6 operators, the description is at most qualitative. We also comment on the applicability of EFT techniques to dark sector phase transitions.