Revisiting constraints on magnetogenesis from baryon asymmetry

Abstract

Magnetic fields in the universe potentially serve as a messenger of primordial physics. The observationally suggested intergalactic magnetic fields may be a relic of helical primordial $\mathrm{U}(1)_Y$ magnetic fields, which may also explain the origin of the baryon asymmetry of the universe. This scenario has been considered to be not viable, which we revisit as well as the baryon isocurvature problem for non-helical primordial $\mathrm{U}(1)_Y$ magnetic fields, based on the recent discussion on the hot electroweak theory. We find that maximally helical fields can be the origin of both the intergalactic magnetic fields and the baryon asymmetry of the universe and that there can be a window for non-helical fields to explain the origin of the intergalactic magnetic fields if the Higgs dynamics during the electroweak crossover compensate the helicity decay with a $\lesssim10^{-9\text{--}-10}$ precision.