SPHERICALLY SYMMETRICAL SOLUTIONS ADMITTING A SPACELIKE SELF-SIMILAR MOTION

Global properties and causal structure are considered for spherically symmetric, perfect fluid solutions admiting a self-similar motion orthogonal to the four-velocity. The fluid admits a stiff equation of state. The momentum-energy tensor is equivalent to that of a free massless scalar field. All solutions have center singularities, some of which are timelike. In the latter cases, there are regions with negative density covered by Cauchy horizons. Regular boundaries at infinity display an asymptotically Minkowski behavior. Models of "vacuum bubbles" arise by performing a C1 matching with a section of Minkowski space-time along the Cauchy horizon. Generalizations associated with a nonzero cosmological constant are briefly examined.