We discuss the relation between the Ramond-Ramond charges of D-branes and the topology of Chan-Paton vector bundles. We show that a topologically nontrivial normal bundle induces RR charge and thatâ€¦ (More)

Applications of conformal field theory to the theory of fractional quantum Hall systems are discussed. In particular, Laughlin's wave function and its cousins are interpreted as conformal blocks inâ€¦ (More)

We show that one can construct D-branes in parafermionic and WZW theories (and their orbifolds) which have very natural geometrical interpretations, and yet are not automatically included in theâ€¦ (More)

In this note we prove an identity that equates the elliptic genus partition function of a supersymmetric sigma model on the N -fold symmetric product M/SN of a manifoldM to the partition function ofâ€¦ (More)

We show that the anomalous couplings of D-brane gauge and gravitational fields to Ramond-Ramond tensor potentials can be deduced by a simple anomaly inflow argument applied to intersecting D-branesâ€¦ (More)

We analyze the u-plane contribution to Donaldson invariants of a four-manifold X. For b^X) > 1, this contribution vanishes, but for b'z = 1, the Donaldson invariants must be written as the sum of aâ€¦ (More)

We study condensation of closed string tachyons living on defects, such as orbifold fixed planes and Neveu-Schwarz fivebranes. We argue that the high energy density of localized states decreases inâ€¦ (More)

We consider string theory in a time dependent orbifold with a null singularity. The singularity separates a contracting universe from an expanding universe, thus constituting a big crunch followed byâ€¦ (More)

Supersymmetric configurations of type II D-branes with nonzero gauge field strengths in general supersymmetric backgrounds with nonzero B fields are analyzed using the Îºsymmetric worldvolume action.â€¦ (More)