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CMB constraints on U(1) axion warm inflation

Asma Alaei1, Sukannya Bhattacharya2, and Vahid Kamali1,3,4,5

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Phys. Rev. D 113, 123546 – Published 24 June, 2026

DOI: https://doi.org/10.1103/k4vl-wsdr

Abstract

In this work, we propose a model of warm inflation driven by axionlike 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 nontrivial backreaction on the inflaton’s dynamics. Our results are consistent with CMB observations, even for a natural sub-Plankian axion decay constant f≤Mp. 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.

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Phys. Rev. D 113, 123546– Published 24 June, 2026
  • Received 19 January 2026
  • Accepted 29 May 2026
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