| I report on advances in the construction of cosmological models in compactifications of string theory.; First, I investigate the dynamics of moduli in quantum field theory and in string theory, with emphasis on their implications for cosmology. I construct a smoothly bouncing cosmological model on a moving D-brane in a warped geometry. I then describe a new phenomenon in which quantum effects trap moving moduli near loci of enhanced symmetry. This is a dynamical selection mechanism with possible implications for evolution on the space of string vacua. I characterize and explain a surprising enhancement of this effect in the relativistic collisions of D-branes.; I then describe progress in moduli stabilization of perturbative heterotic string compactifications on Calabi-Yau threefolds. The combination of fractional flux from Wilson lines and a hidden-sector gaugino condensate gives rise to a potential that fixes all complex structure moduli, Kahler moduli, and the dilaton, leading to a supersymmetric AdS minimum. This is a step toward controllable de Sitter vacua of the heterotic string.; Finally, using important recent advances in moduli stabilization, I present the first concrete models of inflation in a stabilized string compactification. These models involve the motion of a D3-brane in a warped deformed conifold region of an orientifold compactification of type IIB string theory. I discuss situations in which closely-related models receive corrections from threshold effects in nonperturbative superpotentials. |
