O(d, d)-covariant string cosmology

O(d,d)-Covariant String Cosmology

The recently discovered O(d; d) symmetry of the space of (slowly-varying) cosmo-logical string vacua in d + 1 dimensions is shown to be preserved in the presence of bulk string matter. The existence of O(d; d) conserved currents allows all the equations of string cosmology to be reduced to rst-order diierential equations. The perfect-uid approximation is not invariant under O(d; d) transformati...

String Cosmology

String Cosmology

We present a brief review of recent advances in string cosmology. Starting with the Dilaton-Moduli Cosmology (known also as the Pre Big Bang), we go on to include the effects of axion fields and address the thorny issue of the Graceful Exit in String Cosmology. This is followed by a review of density perturbations arising in string cosmology and we finish with a brief introduction to the impact...

String Cosmology

“Old’ String Theory is a theory of one-dimensional extended objects, whose vibrations correspond to excitations of various target-space field modes including gravity. It is for this reason that strings present the first, up to now, mathematically consistent framework where quantum gravity is unified with the rest of the fundamental interactions in nature. In these lectures I will give an introd...

D-branes, string cosmology, and large extra dimensions

D-branes are fundamental in all scenarios where there are large extra dimensions and the string scale is much smaller than the four-dimensional Planck mass. We show that this current picture predicts a period of inflation on our brane which is driven by the large extra dimensions and the issue of the graceful exit becomes inextricably linked to the problem of the stabilization of the extra dime...