A fundamental difficulty underlying standard FRW cosmologies is the prediction of an initial singularity. Several mechanisms have been proposed in an attempt to solve this problem. Some examples are: a creation-field cosmology, a huge vacuum energy density at very early times, quadratic Lagrangians for the gravitational field, nonminimal couplings, nonequilibrium thermodynamic effects and quantum-gravitational phenomena. In this work we investigate the possibility of avoiding the cosmic initial singularity as a consequence of nonlinear effects on the Maxwell electromagnetic theory. For a FRW geometry we derive the general nonsingular solution in the absence of a vacuum energy density. The form of this analytic extension of the FRW model is not significantly altered by the presence of a nonvanishing vacuum energy density and nonsingular behavior of solutions with a time-dependent L(t)-term are also examined. All models, are examples of bouncing universes which may exhibit an inflationary dynamics driven by the nonlinear corrections of the magnetic field.
Bulletin of the Astronomical Society of Brazil
- Pub Date:
- August 2003