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

## TL;DR

This paper constructs an anisotropic SD2 brane solution from type IIA string theory, demonstrating that its compactification results in accelerating cosmologies with directional differences and Kasner-like behavior at early times, including all positive Kasner exponents.

## Contribution

It introduces a new anisotropic SD2 brane solution and shows its compactification yields novel accelerating and Kasner-like cosmologies with positive Kasner exponents.

## Key findings

- Accelerating cosmologies with directional expansion and acceleration.
- Kasner-like early-time cosmology with all positive Kasner exponents.
- Explicit connection between anisotropic brane solutions and four-dimensional cosmological models.

## 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.