| In the first three chapters of this thesis, I will describe a model of inflation based on the dynamics of D3 and D7 branes in type IIB string theory compactified on a K3xT2/Z_2 K orientifold. I will describehow the inflation direction can remain relatively flat from the point of view of four dimensional N=2 supergravity. I will also discuss the formation of cosmic strings at the end of inflation.; The fourth chapter discusses the search for deSitter vacua in toy model compactifications of M-theory on manifolds of G_2 holonomy. We compute the masses of all the moduli at the unstable deSitter critical points and discuss possible cosmological uses for such fields.; In the last part of the thesis, I describe a generalization of the black hole attractor mechanism from Calabi-Yau manifolds to SU(3)xSU(3) structure manifolds. The formalism accommodates non-Kahler manifolds as well as manifolds with background flux. The analysis is carried out in the ten dimensional type II supergravities and makes crucial use of pure spinor techniques. At the attractor fixed point, we show that a generalized black hole attractor equation holds which can be solved using a theorem of Hitchin. |
