ANISOTROPIC GENERALIZATIONS OF THE FRW STRING BACKGROUNDS

An entire class of non-isotropic generalizations of the FRW string bac kgrounds is presented, essentially supplying the string-cosmology coun terpart of the diagonal Bianchi-type models in general relativity. Lea ding-order solutions with vanishing cosmological constant and time-dep ended axion/dilaton scalars have been found for all types. They includ e as special cases all hitherto known solutions within this class, whi le the limits of SO(3) isotropy supply all possible FRW backgrounds. T here is always an initial singularity and no inflation. Other features of the solutions which can illuminate the impact of spatial anisotrop ies on the dynamics of the early universe, as well as their behaviour under abelian T-duality, are discussed.