COSMOLOGY WITH BULK PRESSURE

It is well known that cosmological particle production processes may p henomenologically be described in terms of effective viscous pressures . We investigate the consistency of this approach on the level of rela tivistic kinetic theory, using a Boltzmann equation with an additional source term that leads to a change in the number of gas particles. Fo r 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 p ossibility of a bulk pressure driven inflationary phase within causal, nonequilibrium thermodynamics.