Did our Universe Tunnel out of the Wrong Higgs Vacuum?

TL;DR

This paper investigates the early universe's Higgs field configuration, proposing that a transition from a 'wrong' vacuum could explain inflation and produce detectable gravitational waves, offering new insights into cosmology and particle physics.

Contribution

It introduces the idea that the Higgs field's dynamics during reheating could trigger a first-order phase transition, generating observable gravitational waves and connecting Higgs physics with early universe cosmology.

Findings

A first-order phase transition can occur due to the Higgs potential barrier at high temperatures.

Such a transition produces ultra-high frequency gravitational waves detectable by future experiments.

The Higgs field dynamics could explain inflation and influence dark matter and baryogenesis scenarios.

Abstract

This paper explores various aspects and implications of the initial configuration of the Standard Model (SM) Higgs field at the beginning of our Universe. It is well known that the SM Higgs field features a deeper, more stable minimum at large field values. While it is possible that our Universe began and remained in the electroweak vacuum at all times, this scenario is extremely fine-tuned from the point of view of initial conditions. This fine-tuning can be ameliorated by the exponential expansion of spacetime during inflation: intriguingly, this requires at least $\sim 40$ e-folds of inflation, tantalizingly close to the $50-60$ e-folds expected from horizon and flatness considerations. The Higgs could thus provide the reason for a prolonged epoch of inflation in our cosmic history. Otherwise, the most natural initial state corresponds to our Universe initialized in the more stable but "wrong" Higgs vacuum, and subsequently driven dynamically to the weak scale vacuum during reheating. An important, hitherto unexplored aspect of this dynamics is that the barrier between the two vacua persists when the electroweak vacuum becomes energetically favorable, becoming arbitrarily small as the temperature increases, and therefore triggers a first-order phase transition. This transition produces ultra-high (megahertz to gigahertz) frequency gravitational waves (GWs), serving as a challenging but unique SM target for GW experiments. Novel pathways for various beyond the Standard Model phenomena such as the production of dark matter and baryon asymmetry also become possible in this configuration.