String defects, supersymmetry and the Swampland

The String Landscape and the Swampland

Recent developments in string theory suggest that string theory landscape of vacua is vast. It is natural to ask if this landscape is as vast as allowed by consistent-looking effective field theories. We use universality ideas from string theory to suggest that this is not the case, and that the landscape is surrounded by an even more vast swampland of consistent-looking semiclassical effective...

On the Geometry of the String Landscape and the Swampland

We make a number of conjectures about the geometry of continuous moduli parameterizing the string landscape. In particular we conjecture that such moduli are always given by expectation value of scalar fields and that moduli spaces with finite non-zero diameter belong to the swampland. We also conjecture that points at infinity in a moduli space correspond to points where an infinite tower of m...

1. Supersymmetry and String Theory

Lattice Supersymmetry and String Phenomenology

String phenomenology would benefit from lattice supersymmetry. Without stabilization of moduli, very little predictivity exists in semi-realistic (supersymmetric) string-derived models. The details of stabilization schemes are always somewhat “iffy” because of nonholomorphic quantities in the effective theory (things that depend on the Kähler potential K, such as soft masses, B-terms, A-terms, ...

String Theory, Unification and Supersymmetry

One cannot yet point to any firm string prediction. While many approximate string ground states are known with interesting properties, we do not have any argument that one or another describes what we observe around us, and for reasons which appear fundamental we do not know how to systematically determine even any rough quantitative properties. I argue here that we should examine large classes...