Standard Model thermodynamics across the electroweak crossover

TL;DR

This paper investigates the thermodynamic behavior of the Standard Model around the electroweak crossover temperature, providing detailed results that can impact cosmological models involving dark matter and leptogenesis.

Contribution

It offers the first detailed lattice-based thermodynamic functions across the electroweak crossover, including a numerical table for cosmological applications.

Findings

Deviations from ideal gas thermodynamics near 160 GeV.

QCD effects significantly influence energy density, reducing it by a few percent.

Higgs dynamics create a non-trivial structure in heat capacity.

Abstract

Even though the Standard Model with a Higgs mass mH = 125 GeV possesses no bulk phase transition, its thermodynamics still experiences a "soft point" at temperatures around T = 160 GeV, with a deviation from ideal gas thermodynamics. Such a deviation may have an effect on precision computations of weakly interacting dark matter relic abundances if their mass is in the few TeV range, or on leptogenesis scenarios operating in this temperature range. By making use of results from lattice simulations based on a dimensionally reduced effective field theory, we estimate the relevant thermodynamic functions across the crossover. The results are tabulated in a numerical form permitting for their insertion as a background equation of state into cosmological particle production/decoupling codes. We find that Higgs dynamics induces a non-trivial "structure" visible e.g. in the heat capacity, but that in general the largest radiative corrections originate from QCD effects, reducing the energy density by a couple of percent from the free value even at T > 160 GeV.