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- Cecilia Albertsson, Ulf Lindström, Maxim Zabzine
- 2002

We consider the N = 1 supersymmetric two-dimensional non-linear sigma model with boundaries and nonzero B-field. By analysing the appropriate currents we describe the full set of boundary conditions compatible with N = 1 supercon-formal symmetry. Using this result the problem of finding a correct action is discussed. We interpret the supersymmetric boundary… (More)

- Cecilia Albertsson, Ulf Lindström, Maxim Zabzine
- 2001

We study an N = 1 two-dimensional non-linear sigma model with boundaries representing, e.g., a gauge fixed open string. We describe the full set of boundary conditions compatible with N = 1 superconformal symmetry. The problem is analysed in two different ways: by studying requirements for invariance of the action, and by studying the conserved… (More)

- J Isberg, U Lindström, B Sundborg, G Theodoridis
- 1994

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)

- Parviz Haggi-Mani, Ulf Lindström
- 2000

We discuss the non-linear sigma model representing a NSR open string in a curved background with non-zero B µν-field. With this coupling the theory is not automatically supersymmetric, due to boundary contributions. When B = 0 supersymmetry is ensured by the conditions that follow as the boundary contribution to the field equations. We show that inclusion… (More)

- Ulf Lindström, Martin Roček, Peter van Nieuwenhuizen
- 2008

We study boundary conditions for the bosonic, spinning (NSR) and Green-Schwarz open string, as well as for 1 + 1 dimensional supergravity. We consider boundary conditions that arise from (1) extremizing the action, (2) BRST, rigid or local supersymmetry, or κ(Siegel)-symmetry of the action, (3) closure of the set of boundary conditions under the symmetry… (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)

- U. Lindström
- 2002

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)

- Ulf Lindström, Martin Roček, Rikard von Unge, Maxim Zabzine
- 2005

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)