It is shown that in transitively self-similar spatially homogeneous tilted perfect fluid models the symmetry vector is not normal to the surfaces of spatial homogeneity. A direct consequence of this result is that there are no self-similar Bianchi VIII and IX tilted perfect fluid models. Furthermore the most general Bianchi VIII and IX spacetime which admits a four dimensional group of homotheties is given.
机构:
Penn State Univ, Inst Gravitat & Cosmos, Dept Phys, University Pk, PA 16802 USAPenn State Univ, Inst Gravitat & Cosmos, Dept Phys, University Pk, PA 16802 USA