Axion inflation entails a coupling of the inflaton field to gauge fields through the Chern-Simons term. This results in a strong gauge field production during inflation, which backreacts on the inflaton equation of motion. Here we show that this strongly non-linear system generically experiences a resonant enhancement of the gauge field production, resulting in oscillatory features in the inflaton velocity as well as in the gauge field spectrum. The gauge fields source a strongly enhanced scalar power spectrum at small scales, exceeding previous estimates. For appropriate parameter choices, the collapse of these over-dense regions can lead to a large population of (light) primordial black holes with remarkable phenomenological consequences.
@article{arxiv.2002.02952,
title = {Resonant backreaction in axion inflation},
author = {Valerie Domcke and Veronica Guidetti and Yvette Welling and Alexander Westphal},
journal= {arXiv preprint arXiv:2002.02952},
year = {2020}
}
Comments
LaTeX, 2+32 pages, 11 figures; appendix C added, version accepted by JCAP