Cosmological magnetic fields by parametric resonance?
  We investigate the possibility that electromagnetic fluctuations are amplified in expanding universe by parametric resonance, during the oscillatory regime of a scalar field to which they are coupled. We consider scalar electrodynamics and we find that electromagnetic fluctuations undergo exponential instabilities. This mechanism could have some relevance for the problem of large scale primordial magnetic fields. 
F. Finelli (Purdue U. & Univ. of Bologna & INFN, Bologna)