Simple Bianchi cosmologies with anisotropic Segre [1(11,1)] dark energy

In this paper, we use a sample anisotropic but spatially homogeneous metric to look at the properties of Segre type [1(11,1)] universes, that behave like vacuum energy along a spatial plane (two stresses equal to the negative density) but have distinct stress along the third spatial axis. We examine situations with simple relationships between the distinct and degenerate stresses, finding a closed form parameterizations for the case where the distinct stress is equal to zero and finding new conditions in which the case with all stresses equal has a closed form parameterization. We also use numerical methods to illustrate possible behaviors for the case where the distinct stress is the negative of the degenerate stresses.