The Tachyonic Higgs and the Inflationary Universe

TL;DR

This paper discusses how the tachyonic instability of the Higgs field during high-scale inflation can lead to explosive particle production, affecting early universe dynamics and observable cosmological phenomena.

Contribution

It reveals a previously overlooked feature of Higgs tachyonic instability: rapid particle production that impacts inflationary and post-inflationary evolution.

Findings

Higgs particle production is exponentially enhanced during tachyonic instability.

Significant Higgs particle density can influence preheating and subsequent universe evolution.

Implications for cosmic microwave background, gravitational waves, and primordial black holes.

Abstract

The Standard Model Higgs becomes tachyonic at high energy scales according to current measurements. This unstable regime of the Higgs potential can be realized in the early Universe during high scale inflation, potentially with catastrophic consequences. This letter highlights a crucial inherent feature of such configurations that has so far remained ignored: Higgs particle production out of vacuum induced by the rapidly evolving Higgs field, which gets exponentially enhanced due to the tachyonic instability. Such explosive particle production can rapidly drain energy away from the Higgs field, sustaining a significant density of Higgs particles even during inflation, and could initiate a qualitatively different form of preheating in parts of the post-inflationary Universe. Any study of the Higgs field in its tachyonic phase, either during or after inflation, must therefore take this substantial particle energy density into account, which could significantly affect the subsequent evolution of such systems. This could carry important implications for high scale inflation, post-inflationary preheating, observable signals in the cosmic microwave background, gravitational waves, and primordial black holes, as well as deeper concepts ranging from eternal inflation to the metastability of the electroweak vacuum.