A scenario for inflationary magnetogenesis without strong coupling
  problem
  Cosmological magnetic fields pervade the entire universe, from small to large
scales. Since they apparently extend into the intergalactic medium, it is
tantalizing to believe that they have a primordial origin, possibly being
produced during inflation. However, finding consistent scenarios for
inflationary magnetogenesis is a challenging theoretical problem. The
requirements to avoid an excessive production of electromagnetic energy, and to
avoid entering a strong coupling regime characterized by large values for the
electromagnetic coupling constant, typically allow one to generate only a tiny
amplitude of magnetic field during inflation. We propose a scenario for
building gauge-invariant models of inflationary magnetogenesis potentially free
from these issues. The idea is to derivatively couple a dynamical scalar, not
necessarily the inflaton, to fermionic and electromagnetic fields during the
inflationary era. Such couplings give additional freedom to control the
time-dependence of the electromagnetic coupling constant during inflation. This
fact allows us to find conditions to avoid the strong coupling problems that
affect many of the existing models of magnetogenesis. We do not need to rely on
a particular inflationary set-up for developing our scenario, that might be
applied to different realizations of inflation. On the other hand, specific
requirements have to be imposed on the dynamics of the scalar derivatively
coupled to fermions and electromagnetism, that we are able to satisfy in an
explicit realization of our proposal.
