2,888 research outputs found
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
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 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
Charges and topology in linearised gravity
Covariant conserved 2-form currents for linearised gravity are constructed by
contracting the linearised curvature with conformal Killing-Yano tensors. The
corresponding conserved charges were originally introduced by Penrose and have
recently been interpreted as the generators of generalised symmetries of the
graviton. We introduce an off-shell refinement of these charges and find the
relation between these improved Penrose charges and the linearised version of
the ADM momentum and angular momentum. If the graviton field is globally
well-defined on a background Minkowski space then some of the Penrose charges
give the momentum and angular momentum while the remainder vanish. We consider
the generalisation in which the graviton has Dirac string singularities or is
defined locally in patches, in which case the conventional ADM expressions are
not invariant under the graviton gauge symmetry in general. We modify them to
render them gauge-invariant and show that the Penrose charges give these
modified charges plus certain magnetic gravitational charges. We discuss
properties of the Penrose charges, generalise to toroidal Kaluza-Klein
compactifications and check our results in a number of examples.Comment: 37 pages + appendice
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
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