%0 Journal Article
%T Low energy effective string cosmology
%A E. J. Copeland
%A Amitabha Lahiri
%A David Wands
%J Physics
%D 1994
%I arXiv
%R 10.1103/PhysRevD.50.4868
%X We give the general analytic solutions derived from the low energy string effective action for four dimensional Friedmann-Robertson-Walker models with dilaton and antisymmetric tensor field, considering both long and short wavelength modes of the $H$-field. The presence of a homogeneous $H$-field significantly modifies the evolution of the scale factor and dilaton. In particular it places a lower bound on the allowed value of the dilaton. The scale factor also has a lower bound but our solutions remain singular as they all contain regions where the spacetime curvature diverges signalling a breakdown in the validity of the effective action. We extend our results to the simplest Bianchi I metric in higher dimensions with only two scale factors. We again give the general analytic solutions for long and short wavelength modes for the $H$ field restricted to the three dimensional space, which produces an anisotropic expansion. In the case of $H$ field radiation (wavelengths within the Hubble length) we obtain the usual four dimensional radiation dominated FRW model as the unique late time attractor.
%U http://arxiv.org/abs/hep-th/9406216v2