Ulf Lindstrøm

Learn More
From the ordinary tensile string we derive a geometric action for the tensionless (T = 0) string and discuss its symmetries and field equations. The Weyl symmetry of the usual string is shown to be replaced by a global space-time conformal symmetry in the T → 0 limit. We present the explicit expressions for the generators of this group in the light-cone(More)
  • F Gonzalez-Rey, M Roček, S Wiles, U Lindström, R Von Unge
  • 1997
Manifestly N = 2 supersymmetric Feynman rules are found for different off-shell realiza-tions 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)
The tensionless limit of the free bosonic string is space-time conformally symmetric classically. Requiring invariance of the quantum theory in the light cone gauge tests the reparametrization symmetry needed to fix this gauge. The full conformal symmetry gives stronger constraints than the Poincaré subalgebra. We find that the symmetry may be preserved in(More)
  • H Gustafsson, U Lindström, P Saltsidis, B Sundborg, R V Unge
  • 1994
We present a new formulation of the tensionless string (T = 0) where the space-time conformal symmetry is manifest. Using a Hamiltonian BRST scheme we quantize this Conformal String and find that it has critical dimension D = 2. This is in keeping with our classical result that the model describes massless particles in this dimension. It is also consistent(More)
  • C M Hull, U Lindström, L Melo Dos Santos, R Von Unge, M Zabzine
  • 2008
We investigate the topological theory obtained by twisting the N = (2, 2) supersymmetric nonlinear sigma model with target a bihermitian space with torsion. For the special case in which the two complex structures commute, we show that the action is a Q-exact term plus a quasi-topological term. The quasi-topological term is locally given by a closed(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)
The superembedding formalism is used to study correction terms to the dynamics of the M2 brane in a flat background. This is done by deforming the standard embedding constraint. It is shown rigorously that the first such correction occurs at dimension four. Cohomological techniques are used to determine this correction explicitly. The action is derived to(More)
We propose a Wilsonian action compatible with special geometry and higher dimension N = 2 corrections, and show that the holomorphic contribution F to the low energy effective action is independent of the infrared cutoff. We further show that for asymptotically free SU (2) super Yang-Mills theories, the infrared cutoff can be tuned to cancel leading(More)
The harp seal Pagophilus groenlandicus is a major high trophic level predator in the Barents Sea, and to better understand their function in the Barents Sea ecosystem, we need to understand their foraging behaviour during their most intensive feeding period. We analysed the diet composition and prey preference of 184 harp seals and 94 faeces samples,(More)