1. Geography of String Vacua with Minimal (N=1) Supersymmetry Sergei Gukov Heterotic on CY 3-fold M-theory on G2 manifold Type II on CY 3-fold with fluxes/branes F-theory on CY 4-fold the `right’ vacuum

2. Why N=1 String Vacua? Building realistic models of supersymmetric particle physics and gravity New tools in superstring phenomenology (e.g. flux compactifications) New string vacua, new dualities, new semi-classical limits which are not seen by the perturbative string/field theory Non-perturbative dynamics of gauge theories (e.g. important properties of strongly coupled gauge theories, such as confinement and mass gap may be given a simple explanation in M-theory on G 2 manifolds) Related developments in mathematics If we are lucky, we may see some of this physics at LHC!

3. Which String Vacua are Preferred? Topological String Partition Function: [BCOV,Witten] Entropic Principle: Z top = Wave Function String Cosmology: a Toy Model based on recent work with K.Saraikin and C.Vafa asymptotically free theories are preferred!