Inflationary dilaton-axion magnetogenesis

TL;DR

This paper explores how dilaton-axion dynamics during inflation can generate primordial magnetic fields, highlighting the role of axion-photon coupling in creating large seed fields in the weak coupling regime.

Contribution

It introduces a model of inflationary magnetogenesis involving time-dependent dilaton and axion functions, demonstrating the potential of axion-photon coupling to produce significant magnetic seeds.

Findings

Axion-photon coupling enables large seed magnetic fields during inflation.

The form of the function J(a) is crucial for successful magnetogenesis.

Magnetogenesis is feasible even in the weak coupling regime.

Abstract

We discuss the generation of primordial magnetic fields during inflation in the dilaton-axion electromagnetism, in which the dilaton and axion dynamics are introduced in terms of two time dependent functions of the cosmic scale factor, $I(a) F^2/4$ and $J(a) F\tilde{F}/4$, respectively, where $F$ is the electromagnetic field strength and $\tilde{F}$ is its dual. We study the form of $J(a)$ that can generate a large seed magnetic field in the weak coupling regime, $I(a)<1$. Although the $J(a)$ function is model dependent, the axion-photon coupling indeed opens up a new window for a successful inflationary magnetogenesis.