The symmetries of inflationary magnetogenesis and the plasma initial conditions

As soon as the geometry expands quasi-exponentially the plasma sources are customarily tuned to zero as if the duration of the inflationary phase was immaterial for the gauge field fluctuations at large-scale. The serendipitous disappearance of the plasma (or even the partial neglect of its effects) depends on the symmetries of the system which are, in four space-time dimensions and in the simplest Abelian case, the invariance under Weyl rescaling and the electromagnetic duality symmetry. The quantum, thermal and conducting initial conditions of inflationary magnetogenesis are classified and discussed with the aim of determining when plasma effects can be effectively disregarded. The speculative implications of a non-degenerate monopole plasma for the conservation of the large-scale electric flux are briefly examined.