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Speaker: Jakob Moritz, Cornell University
Abstract: I explain how string theory resolves ubiquitous singularities in type IIB flux compactifications (and eventually KKLT de Sitter vacua) via effects that are non-perturbative in the \alpha' expansion of string theory. I will show that these can be understood in detail by mapping them to well known gauge instanton effects in pure 4d N=2 Yang-Mills theory. A perhaps surprising consequence is that the naively 'elementary' D7 brane of type IIB string theory is properly thought of as a bound state of two mutually non-local cosmic defects in six dimensions upon compactification on a curved 4-manifold. Finally, I will argue that the resolution described indicates that KKLT de Sitter vacua can be controlled by a small flux superpotential although the K\"ahler potential may in general receive large corrections which are difficult to compute.