Effective treatment of U(1) gauge field and charged particles in axion inflation

TL;DR

This paper develops a method to incorporate backreaction effects of charged particles on gauge fields in axion inflation, revealing significant suppression of gauge fields and energy transfer to particles, with implications for cosmological phenomena.

Contribution

It introduces a self-consistent formalism treating charged particle backreaction as effective conductivities in axion inflation models.

Findings

Gauge field amplitudes are drastically suppressed.

Charged particles gain more energy as production efficiency increases.

The formalism links inflationary models to baryogenesis and magnetogenesis phenomena.

Abstract

The axionic inflaton with the Chern-Simons coupling may generate U(1) gauge fields and charged particles simultaneously. In order to incorporate the backreaction from the charged particles on the gauge fields, we develop a procedure to obtain an equilibrium solution for the gauge fields by treating the induced current as effective electric and magnetic conductivities. Introducing mean field approximation, and numerically solving self-consistency equations, we find that the gauge field amplitudes are drastically suppressed. Interestingly, as the production becomes more efficient, the charged particles gain a larger part of the transferred energy from the inflaton and eventually dominate it. Our formalism offers a basis to connect this class of inflationary models to a rich phenomenology such as baryogenesis and magnetogenesis.