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.Comment: 4 pages, no figures. Talk given at COSMO 99: 3rd International
Conference on Particle Physics and the Early Universe, Trieste, Italy, 27 Sep
- 3 Oct 199
