Cosmologies with a noninteracting mixture of dust and radiation

In this paper a particular class of anisotropic cosmologies, the Kantowski--Sachs models, is considered. It is assumed that the matter content of the models consists of a noninteracting mixture of ordinary matter (''dust'') and thermal radiation. A qualitative study by means of a three-dimensional autonomous system is carried out, giving us the global behavior of the ''dust'' density, the radiation density, and the shear anisotropy during the models' evolution. All the models have past and future cosmological singularities where both the dust density and the radiation density diverge. A particular interesting result is a set of solutions of three-measure zero, which is radiation dominated at one (past) singularity (of the ''point'' type) and evolving to a (future) singularity, where ordinary matter and thermal radiation become negligible