78 research outputs found
Strings, gravity and particle physics
This contribution, aimed mostly at experimental particle physicists, reviews
some of the main ideas and results of String Theory in a non-technical
language. It originates from the talks presented by the authors at the
Electro-Weak session of the 2002 Moriond Meeting, here merged in an attempt to
provide a more complete and concise view of the subject.Comment: LaTeX, 28 pages, 13 figures. Contribution to the proceedings of the
2002 Rencontres de Moriond "Electroweak interactions and unified theories
An N=2 worldsheet approach to D-branes in bihermitian geometries: I. Chiral and twisted chiral fields
We investigate N=(2,2) supersymmetric nonlinear sigma-models in the presence
of a boundary. We restrict our attention to the case where the bulk geometry is
described by chiral and twisted chiral superfields corresponding to a
bihermitian bulk geometry with two commuting complex structures. The D-brane
configurations preserving an N=2 worldsheet supersymmetry are identified.
Duality transformations interchanging chiral for twisted chiral fields and vice
versa while preserving all supersymmetries are explicitly constructed. We
illustrate our results with various explicit examples such as the WZW-model on
the Hopf surface S3xS1. The duality transformations provide e.g new examples of
coisotropic A-branes on Kahler manifolds (which are not necessarily
hyper-Kahler). Finally, by dualizing a chiral and a twisted chiral field to a
semi-chiral multiplet, we initiate the study of D-branes in bihermitian
geometries where the cokernel of the commutator of the complex structures is
non-empty.Comment: LaTeX, 50 page
Deformations of Chiral Two-Forms in Six Dimensions
Motivated by a system consisting of a number of parallel M5-branes, we study
possible local deformations of a chiral two-form in six dimensions. Working to
first order in the coupling constant, this reduces to the study of the local
BRST cohomological group at ghost number zero. We obtain an exhaustive list of
all possible deformations. None of them allows for a satisfactory formulation
of the M5-branes system leading to the conclusion that no local field theory
can describe such a system.Comment: 7 pages, LaTeX, minor corrections, assumptions more clearly stated,
final version which will appear in Phys. Lett.
The Geometry of Supersymmetric Sigma-Models
We review non-linear sigma-models with (2,1) and (2,2) supersymmetry. We
focus on off-shell closure of the supersymmetry algebra and give a complete
list of (2,2) superfields. We provide evidence to support the conjecture that
all N=(2,2) non-linear sigma-models can be described by these fields. This in
its turn leads to interesting consequences about the geometry of the target
manifolds. One immediate corollary of this conjecture is the existence of a
potential for hyper-Kahler manifolds, different from the Kahler potential,
which does not only allow for the computation of the metric, but of the three
fundamental two-forms as well. Several examples are provided: WZW models on
SU(2) x U(1) and SU(2) x SU(2) and four-dimensional special hyper-Kahler
manifolds.Comment: 8 pages, LaTeX, contribution to the proceedings of the workshop Gauge
Theories, Applied Supersymmetry and Quantum Gravity, Imperial College,
London, 199
Geometry and beta-functions for N=2 matter models in two dimensions
We study renormalizable nonlinear sigma-models in two dimensions with N=2
supersymmetry described in superspace in terms of chiral and complex linear
superfields. The geometrical structure of the underlying manifold is
investigated and the one-loop divergent contribution to the effective action is
computed. The condition of vanishing beta-function allows to identify a class
of models which satisfy this requirement and possess N=4 supersymmetry.Comment: latex file, 20 pages, no figure
Non-Abelian Born-Infeld Versus String Theory
non-abelian Born-Infeld theory, defined by the symmetrized trace prescription, on tori with constant magnetic fields turned on. Subsequently, we compare this for several cases to the mass spectrum of intersecting D-branes. Exact agreement is found in only two cases: BPS configurations on the four-torus and coinciding tilted branes. Finally we investigate the fluctuation dynamics of an arbitrarily wrapped Dp-brane with flux.Physic
Chiral forms and their deformations
We systematically study deformations of chiral forms with applications to
string theory in mind. To first order in the coupling constant, this problem
can be translated into the calculation of the local BRST cohomological group at
ghost number zero. We completely solve this cohomology and present detailed
proofs of results announced in a previous letter. In particular, we show that
there is no room for non-abelian, local, deformations of a pure system of
chiral p-forms.Comment: 25 pages, LaTe
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