Postinflationary vacuum instability and Higgs-inflaton couplings

TL;DR

This paper investigates how Higgs-inflaton couplings during the early Universe's preheating phase can destabilize the electroweak vacuum, using lattice simulations to identify safe coupling ranges.

Contribution

It provides the first detailed analysis of Higgs dynamics during preheating, establishing bounds on Higgs-inflaton couplings to prevent vacuum instability.

Findings

Resonances can cause large Higgs fluctuations leading to vacuum decay

Identifies upper bounds on Higgs-inflaton couplings for stability

Finds a range of couplings that stabilize the Higgs during inflation and preheating

Abstract

The Higgs-inflaton coupling plays an important role in the Higgs field dynamics in the early Universe. Even a tiny coupling generated at loop level can have a dramatic effect on the fate of the electroweak vacuum. Such Higgs-inflaton interaction is present both at the trilinear and quartic levels in realistic reheating models. In this work, we examine the Higgs dynamics during the preheating epoch, focusing on the effects of the parametric and tachyonic resonances. We use lattice simulations and other numerical tools in our studies. We find that the resonances can induce large fluctuations of the Higgs field which destabilize the electroweak vacuum. Our considerations thus provide an upper bound on quartic and trilinear interactions between the Higgs and the inflaton. We conclude that there exists a favourable range of the couplings within which the Higgs field is stabilized during both inflation and preheating epochs.