Chiral Magnetic Fields and Gravitational Waves

In the early universe, asymmetry in the number density between right and left-handed fermions causes chiral magnetic fields to grow exponentially due to the chiral magnetic effect. Since the total chirality of both the magnetic field and fermions is conserved, the asymmetry limits the maximum strength of these magnetic fields due to this effect. Updated values for effective neutrino count, primordial hydrogen abundance and baryon-photon ratio allow us to constrain the lepton asymmetry due to neutrino species and compute new limits on primordial chiral magnetic fields. We also compute the energy and polarization of gravitational waves generated by these helical sources and compare them to current detection prospects.