287 research outputs found
Branes and Electric-Magnetic Duality in Supersymmetric QCD
We study the Type IIA limit of the M theory fivebrane configuration
corresponding to N=1 supersymmetric QCD with massless quarks. We identify the
effective gauge coupling constant that fits with
Novikov-Shifman-Veinshtein-Zakharov exact beta function. We find two different
Type IIA limits that correspond to the electric and magnetic descriptions of
SQCD, as observed in the massive case by Schmaltz and Sundrum. The analysis is
extended to the case of symplectic and orthogonal gauge groups. In any of the
cases considered in this paper, the electric and magnetic configurations are
smoothly interpolated via theory. This is in sharp contrast with the
proposed derivation of N=1 duality within the weakly coupled Type IIA string
theory where a singularity is inevitable unless one turns on a parameter that
takes the theory away from an interesting point.Comment: 51 pages, 15 figures, LaTeX, minor correction
On The Structure Of The Chan-Paton Factors For D-Branes In Type II Orientifolds
We determine the structure of the Chan-Paton factors of the open strings
ending on space filling D-branes in Type II orientifolds. Through the analysis,
we obtain a rule concerning possible distribution of O-plane types. The result
is applied to classify the topology of D-branes in terms of Fredholm operators
and K-theory, deriving a proposal made earlier and extending it to more general
cases. It is also applied to compactifications with N=1 supersymmetry in
four-dimensions. We adapt and develop the language of category in this context,
and use it to describe some decay channels.Comment: 137 page
Worldsheet Descriptions of Wrapped NS Five-Branes
We provide a world-sheet description of Neveu-Schwarz five-branes wrapped on
a complex projective space. It is an orbifold of the product of an N=2 minimal
model and the IR fixed point of a certain linear sigma model. We show how the
naked singularity in the supergravity description is resolved by the
world-sheet CFT. Applying mirror symmetry, we show that the low-energy theory
of NS5-branes wrapped on CP^1 in Eguchi-Hanson space is described by the
Seiberg-Witten prepotential for N=2 super-Yang-Mills, with the gauge group
given by the ADE-type of the five-brane. The world-sheet CFT is generically
regular, but singularities develop precisely at the Argyres-Douglas points and
massless monopole points of the space-time theory. We also study the low-energy
theory of NS5-branes wrapped on CP^2 in a Calabi-Yau 3-fold and its relation to
(2,2) super-Yang-Mills theory in two dimensions.Comment: 40 pages, late
Duality of the fermionic 2d black hole and N = 2 Liouville theory as mirror symmetry
We prove the equivalence of the SL(2, R)/U(1) Kazama-Suzuki model, which is a fermionic generalization of the 2d Black Hole, and N = 2 Liouville theory. We show that this duality is an example of mirror symmetry. The essential part of the derivation is to realize the fermionic 2d Black Hole as the low energy limit of a gauged linear sigma-model. Liouville theory is obtained by dualizing the charged scalar fields and taking into account the vortex-instanton effects, as proposed recently in non-dilatonic models. The gauged linear sigma-model we study has many useful generalizations which we briefly discuss. In particular, we show how to construct a variety of dilatonic superstring backgrounds which generalize the fermionic 2d Black Hole and admit a mirror description in terms of Toda-like theories
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