Weyl invariance and the conductivity of the protoinflationary plasma
  We consider a globally neutral Lorentzian plasma as a possible remnant of a
preinflationary stage of expansion and pose the problem of the suitable initial
conditions for the evolution of the large-scale electromagnetic
inhomogeneities. During the protoinflationary regime the Weyl invariance of the
Ohmic current guarantees that the comoving conductivity is approximately
constant. The subsequent breaking of Weyl invariance by the masses of the
charge carriers drives the conductivity to zero. The newly derived conducting
initial conditions for the amplification of large-scale magnetic fields are
contrasted with the conventional vacuum initial conditions. It is shown, in a
specific class of examples, that when the number of inflationary efolds is
close to minimal the effects of the conducting initial conditions cannot be
neglected.
