CMB constraints on $U(1)$ axion warm inflation

Abstract

In this work, we propose a model of warm inflation driven by axion-like particles interacting with $U(1)$ gauge fields, with implications for the early universe's thermal evolution. By extending traditional warm inflation models, we introduce a dissipation mechanism through the thermal fluctuations of electromagnetic fields, leading to a non-trivial backreaction on the inflaton's dynamics. Our results are consistent with CMB observations, even for a natural sub-Plankian axion decay constant $f<M_{\rm Pl}$. We present precise constraints on the model's free parameters, using CAMB and CosmoMC codes. These findings offer new insights into the thermal history of the universe and the nature of inflationary dynamics.