Late Time Cosmology With String Gases

By Scott Watson, Brown University

The Brandenberger-Vafa Scenario (a.k.a. Brane Gas Cosmology) posits that by considering the effects of closed strings on a time dependent background, one is led naturally to an universe in which three dimensions have grown large and isotropic, while the other six remain compactified and stable at the self-dual radius. We will review this dynamical mechanism and see that the dilaton plays a crucial role. We will then discuss the late time behavior, when the dilaton must be highly restricted to agree with observational constraints. We will see that radion stabilization will no longer be possible generically, but that this can lead to interesting physics. For example, we will find a new form for dark matter, similar to that recently proposed by Gubser and Peebles.