We apply zeta-function regularization to the kink and susy kink and compute its quantum mass. We fix ambiguities by the renormalization condition that the quantum mass vanishes as one lets the massâ€¦ (More)

We reanalyse the question whether the quantum Bogomolnyi bound is saturated in the two-dimensional supersymmetric kink and sine-Gordon models. Our starting point is the usual expression for theâ€¦ (More)

Turning on background fields in string theory sometimes has an alternative interpretation as a deformation of the target space geometry. A particularly well-known case is the NS-NS two form B, whichâ€¦ (More)

We construct a covariant quantum superstring, extending Berkovitsâ€™ approach by introducing new ghosts to relax the pure spinor constraints. The central charge of the underlying Kac-Moody algebra,â€¦ (More)

We fix the long-standing ambiguity in the 1-loop contribution to the mass of a 1+1-dimensional supersymmetric soliton by adopting a set of boundary conditions which follow from the symmetries of theâ€¦ (More)

We present a new development in our approach to the covariant quantization of superstrings in 10 dimensions which is based on a gauged WZNW model. The WZNW action reduces to our earlier free-fieldâ€¦ (More)

In these lectures, which are written at an elementary and pedagogical level, we discuss general aspects of (single) instantons in SU(N) Yang-Mills theory, and then specialize to the case of N = 4â€¦ (More)

We introduce the notion of a fused quantum superplane by allowing for terms Î¸Î¸ âˆ¼ x in the defining relations. We develop the differential calculus for a large class of fused quantum superplanesâ€¦ (More)

We show how to gauge the set of raising and lowering generators of an arbitrary Lie algebra. We consider SU(N) as an example. The nilpotency of the BRST charge requires constraints on the ghostsâ€¦ (More)

We construct the path integral for one-dimensional non-linear sigma models, starting from a given Hamiltonian operator and states in a Hilbert space. By explicit evaluation of the discretizedâ€¦ (More)