FRW-TYPE COSMOLOGIES WITH ADIABATIC MATTER CREATION

Some properties of cosmological models with matter creation are invest igated in the framework of the Friedmann-Robertson-Walker line element . For adiabatic matter creation, as developed by Prigogine and co-work ers, we derive a simple expression relating the particle number densit y n and energy density p which holds regardless of the matter creation rate. The conditions to generate inflation are discussed and by consi dering the natural phenomenological matter creation rate psi = 3 beta nH, where beta is a pure number of the order of unity and H is the Hub ble parameter, a minimally modified hot big-bang model is proposed. Th e dynamic properties of such models can be deduced from the standard o nes simply by replacing the adiabatic index gamma of the equation of s tate by an effective parameter gamma = gamma(1 - beta). The thermodyn amic behavior is determined and it is also shown that ages large enoug h to agree with observations are obtained even given the high values o f H suggested by recent measurements.