The Cosmology of M-Theory and Type II Superstrings
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We review cosmological solutions of type II superstrings and M-theory, emphasizing the role of non-vanishing Ramond form backgrounds. Compactifications on flat and, more generally, maximally symmetric spatial subspaces are presented. We give a physical discussion of both inflating and subluminally expanding cosmological solutions of such theories and explore their singularity structure. An explicit example, in the context of the type IIA superstring, is constructed. We then analyze compactifications of M-theory on Ricci flat manifolds. The external part of U--duality and its relation to cosmological solutions is studied in the low energy theory. In particular, we investigate the behaviour of important cosmological properties, such as the Hubble parameters and the transition time between two asymptotic regions, under U-duality transformations. Motivated by Horava-Witten theory, we present an explicit example of manifestly U-duality covariant M--theory cosmology in a five-dimensional model resulting from compactification on a Calabi-Yau three-fold.
28 pages, Latex, 3 eps figures, Based on talks given at the Europhysics Conference on High Energy Physics, Jerusalem, Israel, August 1997 and at the XXXIIIrd Rencontres de Moriond, Fundamental Parameters in Cosmology, Les Arcs, Savoie, France, January 1998
28 pages, Latex, 3 eps figures, Based on talks given at the Europhysics Conference on High Energy Physics, Jerusalem, Israel, August 1997 and at the XXXIIIrd Rencontres de Moriond, Fundamental Parameters in Cosmology, Les Arcs, Savoie, France, January 1998