Axion Inflation from Heavy-Fermion One-Loop Effects

TL;DR

This paper develops a one-loop effective theory for axion inflation incorporating heavy-fermion effects, revealing transient gauge-field amplification that could produce detectable gravitational waves.

Contribution

It introduces a novel effective description of axion inflation with heavy-fermion loops, highlighting localized gauge-field production and gravitational wave signals.

Findings

Transient gauge-field production enhances gravitational waves in the deci-hertz band.

The effects remain consistent with primordial black hole constraints.

The model predicts signals within BBO and DECIGO sensitivities.

Abstract

We derive a one-loop effective description of axion inflation by integrating out a heavy Dirac fermion with an inflaton-dependent complex mass undergoing a smooth localized threshold transition. The threshold induces correlated corrections to the inflaton and gauge sectors, including a Coleman-Weinberg term, a vacuum-polarization correction, and an anomaly-induced Chern-Simons coupling. Together, these effects transiently enhance and localize gauge-field production, generating a chiral stochastic gravitational-wave background in the deci-hertz band within the projected sensitivities of BBO and DECIGO, while remaining below representative primordial-black-hole bounds.