Cosmology with bulk pressure

It is well known that cosmological particle production processes may phenomenologically be described in terms of effective viscous pressures. We investigate the consistency of this approach on the level of relativistic kinetic theory, using a Boltzmann equation with an additional source term that leads to a change in the number of gas particles. For a simple creation rate model we find the conditions for collisional equilibrium of a Maxwell-Boltzmann gas with increasing particle number and discuss their cosmological implications. We also comment on the possibility of a bulk pressure driven inflationary phase within causal, nonequilibrium thermodynamics. © Birkhäuser Verlag.