Non-Gaussianity from Cosmic Magnetic Fields

Abstract

Magnetic fields in the early universe could have played an important role in sourcing cosmological perturbations. While not the dominant source, even a small contribution might be traceable through its intrinsic non-Gaussianity. Here we calculate analytically the one, two and three point statistics of the magnetic stress energy resulting from tangled Gaussian fields, and confirm these with numerical realizations of the fields. We find significant non-Gaussianity, and importantly predict higher order moments that will appear between the scalar, vector and tensor parts of the stress energy (e.g. scalar-tensor-tensor moments). Such higher order cross correlations are a generic feature of non-linear theories and could prove to be an important probe of the early universe.