594 research outputs found
T-duality and Generalized Kahler Geometry
We use newly discovered N = (2, 2) vector multiplets to clarify T-dualities
for generalized Kahler geometries. Following the usual procedure, we gauge
isometries of nonlinear sigma-models and introduce Lagrange multipliers that
constrain the field-strengths of the gauge fields to vanish. Integrating out
the Lagrange multipliers leads to the original action, whereas integrating out
the vector multiplets gives the dual action. The description is given both in N
= (2, 2) and N = (1, 1) superspace.Comment: 14 pages; published version: some conventions improved, minor
clarification
Detecting Precipitation Climate Changes: An Approach Based on a Stochastic Daily Precipitation Model
2002 Mathematics Subject Classification: 62M10.We consider development of daily precipitation models based
on [3] for some sites in Bulgaria. The precipitation process is modelled as
a two-state first-order nonstationary Markov model. Both the probability
of rainfall occurrance and the rainfall intensity are allowed depend on the
intensity on the preceeding day. To investigate the existence of long-term
trend and of changes in the pattern of seasonal variation we use a synthesis
of the methodology presented in [3] and the idea behind the classical running
windows technique for data smoothing. The resulting time series of model
parameters are used to quantify changes in the precipitation process over
the territory of Bulgaria
Supersymmetric Oscillator: Novel Symmetries
We discuss various continuous and discrete symmetries of the supersymmetric
simple harmonic oscillator (SHO) in one (0 + 1)-dimension of spacetime and show
their relevance in the context of mathematics of differential geometry. We show
the existence of a novel set of discrete symmetries in the theory which has,
hitherto, not been discussed in the literature on theoretical aspects of SHO.
We also point out the physical relevance of our present investigation.Comment: REVTeX file, 5 pages, minor changes in title, text and abstract,
references expanded, version to appear in EP
Toda Fields on Riemann Surfaces: remarks on the Miura transformation
We point out that the Miura transformation is related to a holomorphic
foliation in a relative flag manifold over a Riemann Surface. Certain
differential operators corresponding to a free field description of
--algebras are thus interpreted as partial connections associated to the
foliation.Comment: AmsLatex 1.1, 10 page
The Lie algebroid Poisson sigma model
The Poisson--Weil sigma model, worked out by us recently, stems from gauging
a Hamiltonian Lie group symmetry of the target space of the Poisson sigma
model. Upon gauge fixing of the BV master action, it yields interesting
topological field theories such as the 2--dimensional Donaldson-Witten
topological gauge theory and the gauged A topological sigma model. In this
paper, generalizing the above construction, we construct the Lie algebroid
Poisson sigma model. This is yielded by gauging a Hamiltonian Lie groupoid
symmetry of the Poisson sigma model target space. We use the BV quantization
approach in the AKSZ geometrical version to ensure consistent quantization and
target space covariance. The model has an extremely rich geometry and an
intricate BV cohomology, which are studied in detail.Comment: 52 pages, Late
Induced Polyakov supergravity on Riemann surfaces of higher genus
An effective action is obtained for the , induced supergravity on a
compact super Riemann surface (without boundary) of genus ,
as the general solution of the corresponding superconformal Ward identity. This
is accomplished by defining a new super integration theory on
which includes a new formulation of the super Stokes theorem and residue
calculus in the superfield formalism. Another crucial ingredient is the notion
of polydromic fields. The resulting action is shown to be well-defined and free
of singularities on \sig. As a by-product, we point out a morphism between
the diffeomorphism symmetry and holomorphic properties.Comment: LPTB 93-10, Latex file 20 page
Canonical differential geometry of string backgrounds
String backgrounds and D-branes do not possess the structure of Lorentzian
manifolds, but that of manifolds with area metric. Area metric geometry is a
true generalization of metric geometry, which in particular may accommodate a
B-field. While an area metric does not determine a connection, we identify the
appropriate differential geometric structure which is of relevance for the
minimal surface equation in such a generalized geometry. In particular the
notion of a derivative action of areas on areas emerges naturally. Area metric
geometry provides new tools in differential geometry, which promise to play a
role in the description of gravitational dynamics on D-branes.Comment: 20 pages, no figures, improved journal versio
W-algebras from symplectomorphisms
It is shown how -algebras emerge from very peculiar canonical
transformations with respect to the canonical symplectic structure on a compact
Riemann surface. The action of smooth diffeomorphisms of the cotangent bundle
on suitable generating functions is written in the BRS framework while a
-symmetry is exhibited. Subsequently, the complex structure of the symmetry
spaces is studied and the related BRS properties are discussed. The specific
example of the so-called -algebra is treated in relation to some other
different approaches.Comment: LaTex, 25 pages, no figures, to appear in Journ. Math. Phy
Generalized structures of N=1 vacua
We characterize N=1 vacua of type II theories in terms of generalized complex
structure on the internal manifold M. The structure group of T(M) + T*(M) being
SU(3) x SU(3) implies the existence of two pure spinors Phi_1 and Phi_2. The
conditions for preserving N=1 supersymmetry turn out to be simple
generalizations of equations that have appeared in the context of N=2 and
topological strings. They are (d + H wedge) Phi_1=0 and (d + H wedge) Phi_2 =
F_RR. The equation for the first pure spinor implies that the internal space is
a twisted generalized Calabi-Yau manifold of a hybrid complex-symplectic type,
while the RR-fields serve as an integrability defect for the second.Comment: 21 pages. v2, v3: minor changes and correction
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