Nonlinearity of electrodynamics as a source of matter creation in a flat FRW cosmology

The thermodynamics of cosmological matter creation has been extensively investigated in the literature. In the context of general relativity, the particle production in the cosmological models is due to mechanisms such as an imperfect fluid with bulk viscosity or the decaying vacuum. Another interesting proposal is matter creation in cosmologies with variation of fundamental constants. In this work, we study the nonlinearity of the electrodynamics as a source of matter creation in cosmological models with. at Friedmann-Robertson-Walker (FRW) line geometry. We write the energy conservation law arising from Einstein field equations with cosmological term Lambda, solve the field equations, and study how particles are created as the magnetic field B changes with cosmic epoch. We obtain solutions for the adiabatic particle creation rate, the total number of particles, and the scale factor as a function of time in three cases: Lambda = 0, Lambda = constant and Lambda proportional to H-2 (cosmological term proportional to the Hubble parameter). We find the constraints imposed by the second law of thermodynamics upon the cosmological solutions.