A Subclass of Exceptional Parallel Self-similar G2 Cosmologies

Abstract

We perform a qualitative and asymptotic analysis of a particular class of cosmological models, namely the exceptional G2 perfect fluid and vacuum models that are additionally self-similar with the fluid flow lying tangential to the H3 orbits. We show that for the values of the equation of state parameter in (1,3/2), there exist open sets of well-behaved vacuum models that are asymptotically spatially homogeneous, at large spatial distances. For the values of the equation of state parameter in the intervals (1,10/9) and (4/3,3/2), there exist open sets of well-behaved perfect fluid inhomogeneous cosmological models that are asymptotically spatially homogeneous, at large spatial distances, and we illustrate the spatial structure of their matter-energy density. In addition, the perfect fluid models exhibit only two possible asymptotic behaviours, namely they are well-behaved and asymptotically spatially homogeneous or badly-behaved.