Non-Gaussianity as a Probe of Primordial Magnetic Fields

Abstract: Recent hints of an intergalactic magnetic field pervading the Universe lend support to a primordial origin for cosmic magnetic fields.  We calculate the non-Gaussianity induced by magnetic fields in the CMB (Cosmic Microwave Background radiation) and find it is a sensitive probe of large-scale primordial magnetic fields. Comparing our theoretical results on the magnetic bispectrum and trispectrum with Planck observations, we place an improved sub-nanoGauss constraint on the present amplitude of large-scale primordial magnetic fields.