Regular homogeneous T-models with vacuum dark fluid

We present the class of regular homogeneous T-models with vacuum dark fluid, associated with a variable cosmological term. The vacuum fluid is defined by the symmetry of its stress-energy tensor, i.e., its invariance under Lorentz boosts in a distinguished spatial direction (pj = -ρ), which makes this fluid essentially anisotropic and allows its density to evolve. Typical features of homogeneous regular T-models are: the existence of a Killing horizon; beginning of the cosmological evolution from a null bang at the horizon; the existence of a regular static pre-bang region visible to cosmological observers; creation of matter from anisotropic vacuum, accompanied by very rapid isotropization. We study in detail the spherically symmetric regular T-models on the basis of a general exact solution for a mixture of the vacuum fluid and dust-like matter and apply it to give numerical estimates for a particular model which illustrates the ability of cosmological T-models to satisfy the observational constraints. © 2007 IOP Publishing Ltd.