I will discuss a qualitatively new possibility for the generation of cosmic magnetic fields in the context of inflation. The mechanism rests on the dynamics of three-forms as inflating fields, whose uniquely gauge-invariant coupling to light gives rise to new solutions in the equations of motion for the latter, which in turn allow for exponential amplification of the photon’s vacuum fluctuations. We will dwell into some details (backreactions, spectrum) as well as present latest developments and potential issues.

University of British Columbia