String cosmologies

A model of a cloud formed by massive strings is studied in the context of the usual general relativity. This model is used as a source of Bianchi type I and "Kantowski-Sachs" type of cosmological models. Some global properties of the above-mentioned cosmological models are studied for the equation of state (energy density) $\propto$ (tension density). Particular models that can be explicitly integrated are also studied. The possibility that during the evolution of the Universe the strings disappear leaving only particles is examined.