Anisotropic SD2 brane: accelerating cosmology and Kasner-like space-time from compactification

Abstract

Starting from an anisotropic (in all directions including the time direction of the brane) non-susy D2 brane solution of type IIA string theory we construct an anisotropic space-like D2 brane (or SD2 brane, for short) solution by the standard trick of double Wick rotation. This solution is characterized by five independent parameters. We show that upon compactification on six dimensional hyperbolic space (H$_6$) of time dependent volume of this SD2 brane solution leads to accelerating cosmologies (for some time $t\sim\,t_0$, with $t_0$ some characteristic time) where both the expansions and the accelerations are different in three spatial directions of the resultant four dimensional universe. On the other hand at early times ($t \ll t_0$) this four dimensional space, under certain situations, leads to four dimensional Kasner-like cosmology, with two additional scalars, namely, the dilaton and a volume scalar of H$_6$. Unlike in the standard four dimensional Kasner cosmology here all three Kasner exponents could be positive definite, leading to expansions in all three directions.