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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)

- 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)

- 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)

- 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)

- 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)

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)