Classification of Uniform Cosmological Models

Homogeneous and isotropic models of relativistic cosmology are classified according to a general scheme. There are four main groups: static, asymptotic, monotonic and oscillatory, and each group is subdivided into classes. Altogether, there are eleven classes of cosmological models. In recent years models have been proposed which contain negative pressure. Robertson's original scheme of classification therefore requires development, as in the present treatment, to take into account the possibility of a negative cosmic stress. As a consequence there emerges a wide variety of cosmological models, including models that are both static and stable and models that oscillate between finite values of density.