Higgs vacuum metastability in $R+R^2$ gravity

TL;DR

This paper investigates how $R+R^2$ gravity influences Higgs vacuum metastability during inflation, providing bounds on the non-minimal coupling and analyzing bubble nucleation effects in a cosmological context.

Contribution

It offers the first detailed analysis of Higgs vacuum stability within $R+R^2$ gravity, deriving bounds on the non-minimal coupling and exploring the impact on inflationary dynamics.

Findings

Lower bounds on the non-minimal coupling $\xi$ derived from effective potential analysis.

Destabilizing terms in the Higgs potential due to $R+R^2$ gravity effects.

Dependence of bubble nucleation on the end stages of inflation.

Abstract

Experimental data suggest that the Higgs potential has a lower ground state at high field values. Consequently, decaying from the electroweak to the true vacuum nucleates bubbles that expand rapidly and can have dire consequences for our Universe. This overview of our last study [1] regarding the cosmological implications of vacuum metastability during Starobinsky inflation was presented at the HEP2023 conference. Following the framework established in [2], we showcased our state-of-the-art lower bounds on the non-minimal coupling $\xi$, which resulted from a dedicated treatment of the effective Higgs potential in $R+R^2$ gravity. The effects of this consideration involved the generation of destabilising terms in the potential and the sensitive dependence of bubble nucleation on the last moments of inflation. In this regime, spacetime deviates increasingly from de Sitter and thus the validity of our approach reaches its limit, but at earlier times, we recover our result hinting against eternal inflation.