Sigma models with off-shell N=(4,4) supersymmetry and noncommuting complex structures

We describe the conditions for extra supersymmetry in N=(2,2) supersymmetric nonlinear sigma models written in terms of semichiral superfields. We find that some of these models have additional off-shell supersymmetry. The (4,4) supersymmetry introduces geometrical structures on the target-space which are conveniently described in terms of Yano f-structures and Magri-Morosi concomitants. On-shell, we relate the new structures to the known bi-hypercomplex structures.Comment: 20 pages; v2: significant corrections, clarifications, and reorganization; v3: discussion of supersymmetry vs twisted supersymmetry added, relevant signs corrected

N=2 Boundary conditions for non-linear sigma models and Landau-Ginzburg models

We study N=2 nonlinear two dimensional sigma models with boundaries and their massive generalizations (the Landau-Ginzburg models). These models are defined over either Kahler or bihermitian target space manifolds. We determine the most general local N=2 superconformal boundary conditions (D-branes) for these sigma models. In the Kahler case we reproduce the known results in a systematic fashion including interesting results concerning the coisotropic A-type branes. We further analyse the N=2 superconformal boundary conditions for sigma models defined over a bihermitian manifold with torsion. We interpret the boundary conditions in terms of different types of submanifolds of the target space. We point out how the open sigma models correspond to new types of target space geometry. For the massive Landau-Ginzburg models (both Kahler and bihermitian) we discuss an important class of supersymmetric boundary conditions which admits a nice geometrical interpretation.Comment: 48 pages, latex, references and minor comments added, the version to appear in JHE

Development of the coefficient of inbreeding and relationship in the finnish ayrshire breed

International audienc

Optical flow estimation on image sequences with differently exposed frames

Optical flow (OF) methods are used to estimate dense motion information between consecutive frames in image sequences. In addition to the specific OF estimation method itself, the quality of the input image sequence is of crucial importance to the quality of the resulting flow estimates. For instance, lack of texture in image frames caused by saturation of the camera sensor during exposure can significantly deteriorate the performance. An approach to avoid this negative effect is to use different camera settings when capturing the individual frames. We provide a framework for OF estimation on such sequences that contain differently exposed frames. Information from multiple frames are combined into a total cost functional such that the lack of an active data term for saturated image areas is avoided. Experimental results demonstrate that using alternate camera settings to capture the full dynamic range of an underlying scene can clearly improve the quality of flow estimates. When saturation of image data is significant, the proposed methods show superior performance in terms of lower endpoint errors of the flow vectors compared to a set of baseline methods. Furthermore, we provide some qualitative examples of how and when our method should be used

Polar supermultiplets, Hermitian symmetric spaces and hyperkahler metrics

We address the construction of four-dimensional N=2 supersymmetric nonlinear sigma models on tangent bundles of arbitrary Hermitian symmetric spaces starting from projective superspace. Using a systematic way of solving the (infinite number of) auxiliary field equations along with the requirement of supersymmetry, we are able to derive a closed form for the Lagrangian on the tangent bundle and to dualize it to give the hyperkahler potential on the cotangent bundle. As an application, the case of the exceptional symmetric space E_6/SO(10) \times U(1) is explicitly worked out for the first time.Comment: 17 page

First-order supersymmetric sigma models and target space geometry

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 uncover a geometrical framework which contains generalized complex geometry as a special case.Comment: 1+19 pages, JHEP style, published versio

On massive tensor multiplets

Massive tensor multiplets have recently been scrutinized in hep-th/0410051 and hep-th/0410149, as they appear in orientifold compactifications of type IIB string theory. Here we formulate several dually equivalent models for massive N = 1, N=2 tensor multiplets in four space-time dimensions. In the N = 2 case, we employ harmonic and projective superspace techniques.Comment: 17 pages, LaTeX, no figures; V2: reference adde

Euclidean Supersymmetry, Twisting and Topological Sigma Models

We discuss two dimensional N-extended supersymmetry in Euclidean signature and its R-symmetry. For N=2, the R-symmetry is SO(2)\times SO(1,1), so that only an A-twist is possible. To formulate a B-twist, or to construct Euclidean N=2 models with H-flux so that the target geometry is generalised Kahler, it is necessary to work with a complexification of the sigma models. These issues are related to the obstructions to the existence of non-trivial twisted chiral superfields in Euclidean superspace.Comment: 8 page

Intersubjectivity at the counter : Artefacts and multimodal interaction in theatre box office encounters

The pesent study investigates the interplay between language, materia land embodied resources in one specific type of service encounters: interactions at theatre box offices. The data consist of video recorded interactions in Swedish at three box offices, two in Sweden and onei n Finland. Cases representative of the interactions are selected for a multimodal micro-analysis of the customer -- seller interactions involving artefacts from the institutional and personal domain. The study specifically aims at advancing our understanding of the role of artefacts for structuring and facilitating communicative events in (institutional) interaction. In this way, it contributes to the growing research interest in the interactional importance of the material world. Our results show that mutual interactional focus is reached through mutual gaze in strategic moments, such as formulation of the reason for the visit. Artefacts are central in enhancing intersubjectivity and mutual focus in that they effectively invite the participants for negotiation, for example, about a seatingplan which can be made visually accessible in different ways. Verbal language can be sparse and deictic in these moments while gaze and pointing to an artefact does more specific referential work. Artefacts are also a resource for signalling interactional inaccessibility, the seller orienting to the computer in order to progress a request and the customer orienting to a personal belonging (like a bag) to mirror and accept such a temporary non-accessibility. We also observe that speech can be paced to match the deployment of an artefact so that a focal verbal item is produced without competing, simultaneous physical activity.Peer reviewe