Cosmological Particle Production and Causal Thermodynamics

The full linear causal Israel{Stewart{Hiscock theory of bulk viscous processes in relativistic cosmological °uids is reformulated as an efiective phenomenological theory for describing particle production processes in the early universe. Explicit expressions for the particle balance law and particle production rates are obtained that relate the particle creation rate to the bulk viscous (creation) pressure. The general formalism is applied to the case of a full causal cosmological °uid with bulk viscosity coe–cient proportional to the Hubble function. In this case the general solution of the gravitational fleld equations can be expressed in an exact parametric form. For an appropriate choice of the physical parameters, the dynamics of the universe can be modelled as starting from a vacuum quasi-Minkowskian geometry, followed by an in°ationary period but ending in a non-in°ationary phase. The in°uence of the matter creation processes on the evolution of the universe and the behaviour of the energy density, temperature and entropy are investigated. 1