Creation of Dirac Particles in the Presence of a Constant Electric Field   in an Anisotropic Bianchi I Universe
  In this article we compute the density of Dirac particles created by a cosmological anisotropic Bianchi I universe in the presence of a constant electric field. We show that the particle distribution becomes thermal when one neglects the electric interaction. 
Victor M. Villalba, Walter Greiner