String theory in particular (here a by now somewhat outdated review paper from 1997) and quantum field theory in general, especially non-perturbative aspects of supersymmetric theories and duality. See also the sites: The Elegant Universe, Beyond String Theory, and the Spiegel-article (in german) about the Strings '99 conference.
Currently my interests are in the quantum geometry of D-branes, in particular in the interplay between open topological strings, mirror symmetry and the Landau-Ginzburg realization of the category of topological branes.
Currently, I am deputy leader of PH-TH, and chair the staff search committee, and will soon chair the Wednesday Colloquium committee.
Here some utilities and infos for MacOSX.