DIRECT ELECTROGRAVITATIONAL COUPLINGS AND THE BEHAVIOR OF PRIMORDIAL LARGE-SCALE MAGNETIC-FIELDS

A comprehensive approach is suggested for describing the origin and ev olution of large-scale magnetic fields. Vorticity-dependent fluctuatio ns acting on a primordial charged plasma account for field generation, and the properties of gauge-invariant (but conformally non-invariant) couplings of electromagnetic and gravitational fields in a FRW backgr ound are applied in order to supply a source-independent, gravity-driv en mechanism of conductance induction in the course of the reheating p hase of inflationary cosmic scenarios. In consequence, the description of the behaviour of large-scale primordial magnetic fields is complem ented so as to cover the whole post-inflationary history of the univer se.