Nonsingular Bianchi type I cosmological solutions from the 1-loop superstring effective action - art. no. 063506

Nonsingular Bianchi type I solutions are found from the effective action wi th a superstring-motivated Gauss-Bonnet term. These anisotropic nonsingular solutions evolve from the asymptotic Minkowski region, subsequently superi nflate, and then smoothly continue either to Kasner-type (expanding in two directions and shrinking in one direction) or to Friedmann-type (expanding in all directions) solutions. We also find a new kind of singularity which arises from the fact that the anisotropic expansion rates are a multiple-va lued function of time. The initial singularity in the isotropic limit of th is model belongs to this new kind of singularity. In our analysis the aniso tropic solutions are likely to be singular when the superinflation is steep . As for the cosmic no-hair conjecture, our results suggest that the kineti c-driven superinflation of our model does not isotropize the space-time. [S 0556-2821(99)02106-2].