Magnetogenesis from axion inflation: old ideas and recent developments

• Oleksandr Sobol

The paradigm of inflation is a very successful idea that not only solves a large number of cosmological problems, but also provides a convincing mechanism for the origin of the primordial perturbations which are the seeds for CMB anisotropies and modern large-scale structure of the Universe. Therefore, it looks very natural to assume that cosmic inflation may also give rise to primordial magnetic fields which could serve as seeds for magnetic fields in galaxies and galaxy clusters and possibly explain the presence of magnetic fields in voids detected in gamma-ray observations from distant blazars. In my talk I will focus on one particular model of inflationary magnetogenesis - the axion inflation - where a pseudoscalar inflaton field is coupled to an Abelian gauge field through the Chern-Simons term. Despite the fact that this idea originates from the early 1990s, it has attracted a lot of attention in the literature in the last years as it has many phenomenological applications (e.g., to baryogenesis, production of gravitational waves, primordial black holes etc.) I will give an overview of methods that are used to describe the gauge-field production during axion inflation and discuss interesting (potentially observable) features arising in the regime of strong backreaction. The talk is based on refs. 2109.01651, 2111.04712, 2303.04583, and current research which is still in progress.