Ulf Lindström

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We solve the long standing problem of finding an off-shell supersymmetric formulation for a general N = (2, 2) nonlinear two dimensional sigma model. Geometrically the problem is equivalent to proving the existence of special coordinates; these correspond to particular superfields that allow for a superspace description. We construct and explain the(More)
On a historical note, we first describe the early superspace construction of counterterms in supergravity and then move on to a brief discussion of selected areas in string theory where higher order supergravity invariants enter the effective theories. Motivated by this description we argue that it is important to understand p-brane actions with κ-invariant(More)
Manifestly N = 2 supersymmetric Feynman rules are found for different off-shell realizations of the massless hypermultiplet in projective superspace. When we reduce the Feynman rules to an N = 1 superspace we obtain the correct component propagators. The Feynman rules are shown to be compatible with a “duality” that acts only on the auxiliary fields, as(More)
This paper presents a projective superspace formulation for 4D N = 2 mattercoupled supergravity. We first describe a variant superspace realization for the N = 2 Weyl multiplet. It differs from that proposed by Howe in 1982 by the choice of the structure group ( SO(3, 1)×SU(2) versus SO(3, 1)×U(2) ) , which implies that the super-Weyl transformations are(More)
Generalized complex geometry is a new mathematical framework that is useful for describing the target space of N = (2, 2) nonlinear sigma-models. The most direct relation is obtained at the N = (1, 1) level when the sigma model is formulated with an additional auxiliary spinorial field. We revive a formulation in terms of N = (2, 2) semi-(anti)chiral(More)
The Green-Schwarz action for an open superstring with additional boundary fermions, representing Chan-Paton factors, is studied at the classical level. The boundary geometry is described by a bundle M̂ , with fermionic fibres, over the super worldvolume M of a D-brane together with a map from M̂ into the N = 2,D = 10 target superspace M . This geometry is(More)
OBJECTIVES Epidemiological studies of spondyloarthritis (SpA), using ICD codes from the Swedish National Patient Register (NPR), offer unique possibilities but hinge upon an understanding of the validity of the codes. The aim of this study was to validate the ICD codes for ankylosing spondylitis (AS) and undifferentiated SpA (uSpA) in the NPR against the(More)
We study the conditions under which N = (1, 1) generalized sigma models support an extension to N = (2, 2). The enhanced supersymmetry is related to the target space complex geometry. Concentrating on a simple situation, related to Poisson sigma models we develop a language that may help us analyze more complicated models in the future. In particular, we(More)