Primordial Weibel instability

Abstract We study the onset of vector instabilities in post-inflationary epoch Universe as a mechanism for primordial magnetic fields amplification. assume presence charged spectator scalar field arbitrarily coupled to gravity during Inflation its vacuum de Sitter state. Gravitational particle creation takes place at transition from subsequent Reheating stage and thus state becomes an excited many particles one. Consequently this can be described real fluid, we build out hydrodynamic framework using second order theories relativistic fluids with relaxation time prescription collision integral. Given high-temperature regime vanishing curvature (radiation-dominated-type era), fluid regarded conformal The large quantum fluctuations induced by rapid inflationary effectively radiation dominated expansion become statistical whereby both charge excess anisotropic pressures are produced any finite domain. precise magnitude effect each scale is determined size averaging domain coupling curvature. look domains which larger than horizon beginning Reheating, but much smaller our own horizon, show that fraction them anisotropy provide suitable conditions Weibel instability. If moreover duration reheating shorter then instability compensate or even overcome dilution field. non-trivial topology encoded helicity also amplified if present.