Generation of the Higgs Condensate and Its Decay after Inflation

TL;DR

This paper studies the behavior of the Higgs field during and after inflation, showing it becomes a light spectator field, its equilibrium value depends on the inflation scale, and it decays mainly through gauge boson production, with potential implications for cosmological perturbations.

Contribution

It provides a detailed analysis of the Higgs condensate dynamics post-inflation, including its equilibrium state, decay channels, and potential impact on cosmological perturbations, which was not thoroughly explored before.

Findings

Higgs becomes a light spectator field after ~30 e-folds of inflation.

Equilibrium Higgs amplitude depends on the inflation scale and self-coupling.

Significant Higgs decay occurs within 340-630 Hubble times after oscillations start.

Abstract

We investigate the dynamics of the Standard Model higgs with a minimal coupling to gravity during and after inflation. In the regime where the Standard Model vacuum is stable, we find that the higgs becomes a light spectator field after about 30 efolds of inflation, irrespectively of its initial value. Once the higgs has become light, its root-mean-square value h_* relaxes to equilibrium in about 85 efolds for the inflationary scale of H_*=10^4 GeV and in 20 efolds for H_*=10^10 GeV. The equilibrium value is given by h_*~0.36 lambda^{-1/4}H_*, where lambda=0.09 ... 0.0005 is the higgs self coupling at the scales H_*=10^4 ... 10^10 GeV. We show that the main decay channel of the higgs condensate after inflation is the resonant production of Standard Model gauge bosons. For a set of parameters we find that a significant part of the condensate has decayed in between 340 and 630 Hubble times after the onset of higgs oscillations, depending on H_* in a non-trivial way. The higgs perturbations correspond to isocurvature modes during inflation but they could generate significant adiabatic perturbations at a later stage for example through a modulation of the reheating stage. However, this requires that the inflaton(s) decay no later than a few hundred Hubble times after the onset of higgs oscillations.