Constraining inflationary magnetogenesis and reheating via GWs in light of PTA data

Abstract

By leveraging the limits on primordial magnetic fields (PMFs), their contributions to secondary gravitational waves (GWs), and the recent observations by the pulsar timing arrays (PTAs), we arrive at constraints on the epoch of reheating. We find that the combined spectral energy density of primary and secondary (generated by the PMFs) GWs can be described as a broken power law with different indices. We show that PMFs with blue spectra and appropriate reheating scenarios can successfully explain the PTA observations without invoking any new physics.