Generalized Kahler Geometry from supersymmetric sigma models

We give a physical derivation of generalized Kahler geometry. Starting from a supersymmetric nonlinear sigma model, we rederive and explain the results of Gualtieri regarding the equivalence between generalized Kahler geometry and the bi-hermitean geometry of Gates-Hull-Rocek. When cast in the language of supersymmetric sigma models, this relation maps precisely to that between the Lagrangian and the Hamiltonian formalisms. We also discuss topological twist in this context.Comment: 18 page

Response distributions when TDE is introduced

Statistics Sweden benutzt Touch-tone Data Entry (TDE) zur Datenerhebung im Rahmen von drei Untersuchungen: Index der Herstellerpreise (PPI), Kurzfristige Umsatzstatistik für den inländischen Handels- und Dienstleistungssektor (STS), Statistik der kommunalen Aufwendungen für Sozialhilfe (MCSA). PPI wird monatlich erstellt, MCSA vierteljährlich, STS liegt sowohl monatlich wie vierteljährlich vor. Alle drei Erhebungen haben verpflichtenden Charakter. Der Einführung von TDE bei PPI ging ein groß angelegtes Experiment voran. Auch für STS und MCSA wurden methodische Untersuchungen durchgeführt. Der Verfasser zeigt, wie sich TDE und Antwortverhalten im Zeitverlauf entwickelt haben und inwieweit sich die Untersuchungen verschiedener Methoden bedienen. Darüber hinaus diskutiert er Gründe für das unterschiedliche Antwortverhalten bei TDE. Bei diesem Bericht handelt es sich um die Kurzfassung eines Berichts für Statistics Sweden, der genaue Daten für MCSA und die monatlichen Antwortverteilungen für 1997 präsentieren wird. (ICEÜbers)"Three surveys at Statistics Sweden use Touch-tone Data Entry (TDE) for their data collection: Producers Price Index (PPI), Short-term Turnover Statistics for Domestic Trade and Services (STS), and Statistics an Municipalities' Costs for Social Assistance (MCSA). PPI is a monthly survey, MCSA is a quarterly and STS has both monthly and quarterly parts. MCSA is a census and the two other surveys use the same sample each month during the year. All three are mandatory surveys. The TDE implementation in PPI was preceded by a large experiment. Methodological studies were also made in STS and MCSA. Details are given to show the development of TDE and overall response rates over time and to what extent the surveys have turned into multimode surveys. The TDE response rates differ in these surveys. This report presents the differences and offers some explanations to them. It is a condensed version of a report written for Statistics Sweden. The complete report will-include the details of MCSA and response distributions for all months of 1997." (author's abstract

Analysis of high quality superconducting resonators: consequences for TLS properties in amorphous oxides

$1/f$ noise caused by microscopic Two-Level Systems (TLS) is known to be very detrimental to the performance of superconducting quantum devices but the nature of these TLS is still poorly understood. Recent experiments with superconducting resonators indicates that interaction between TLS in the oxide at the film-substrate interface is not negligible. Here we present data on the loss and $1/f$ frequency noise from two different Nb resonators with and without Pt capping and discuss what conclusions can be drawn regarding the properties of TLS in amorphous oxides. We also estimate the concentration and dipole moment of the TLS.Comment: 8 pages, 5 figure

Properties of hyperkahler manifolds and their twistor spaces

We describe the relation between supersymmetric sigma-models on hyperkahler manifolds, projective superspace, and twistor space. We review the essential aspects and present a coherent picture with a number of new results.Comment: 26 pages. v2: Sign mistakes corrected; Kahler potential explicitly calculated in example; references added. v3: Published version--several small clarifications per referee's reques

The Semi-Chiral Quotient, Hyperkahler Manifolds and T-duality

We study the construction of generalized Kahler manifolds, described purely in terms of N=(2,2) semichiral superfields, by a quotient using the semichiral vector multiplet. Despite the presence of a b-field in these models, we show that the quotient of a hyperkahler manifold is hyperkahler, as in the usual hyperkahler quotient. Thus, quotient manifolds with torsion cannot be constructed by this method. Nonetheless, this method does give a new description of hyperkahler manifolds in terms of two-dimensional N=(2,2) gauged non-linear sigma models involving semichiral superfields and the semichiral vector multiplet. We give two examples: Eguchi-Hanson and Taub-NUT. By T-duality, this gives new gauged linear sigma models describing the T-dual of Eguchi-Hanson and NS5-branes. We also clarify some aspects of T-duality relating these models to N=(4,4) models for chiral/twisted-chiral fields and comment briefly on more general quotients that can give rise to torsion and give an example.Comment: 31 page

Generalized Kahler geometry and gerbes

We introduce and study the notion of a biholomorphic gerbe with connection. The biholomorphic gerbe provides a natural geometrical framework for generalized Kahler geometry in a manner analogous to the way a holomorphic line bundle is related to Kahler geometry. The relation between the gerbe and the generalized Kahler potential is discussed.Comment: 28 page

Relating harmonic and projective descriptions of N=2 nonlinear sigma models

Recent papers have established the relationship between projective superspace and a complexified version of harmonic superspace. We extend this construction to the case of general nonlinear sigma models in both frameworks. Using an analogy with Hamiltonian mechanics, we demonstrate how the Hamiltonian structure of the harmonic action and the symplectic structure of the projective action naturally arise from a single unifying action on a complexified version of harmonic superspace. This links the harmonic and projective descriptions of hyperkahler target spaces. For the two examples of Taub-NUT and Eguchi-Hanson, we show how to derive the projective superspace solutions from the harmonic superspace solutions.Comment: 25 pages; v3: typo fixed in eq (1.36

An Alternative Topological Field Theory of Generalized Complex Geometry

We propose a new topological field theory on generalized complex geometry in two dimension using AKSZ formulation. Zucchini's model is $A$ model in the case that the generalized complex structuredepends on only a symplectic structure. Our new model is $B$ model in the case that the generalized complex structure depends on only a complex structure.Comment: 29 pages, typos and references correcte