186,776 research outputs found
N=1 Matter from Fractional Branes
We study a bound state of fractional D3-branes localized inside the
world-volume of fractional D7-branes on the orbifold C^3/Z_2 x Z_2. We
determine the open string spectrum that leads to N=1 U(N1)xU(N2)xU(N3)xU(N4)
gauge theory with matter having the number of D7-branes as a flavor index. We
derive the linearized boundary action of the D7-brane on this orbifold using
the boundary state formalism and we discuss the tadpole cancellation. After
computing the asymptotic expression of the supergravity solution the anomalies
of the gauge theory are reproduced.Comment: LaTeX 20 pages, 1 figure, small changes and references adde
Yangians in Deformed Super Yang-Mills Theories
We discuss the integrability structure of deformed, four-dimensional N=4
super Yang-Mills theories using Yangians. We employ a recent procedure by
Beisert and Roiban that generalizes the beta deformation of Lunin and Maldacena
to produce N=1 superconformal gauge theories, which have the superalgebra
SU(2,2|1)xU(1)xU(1). The deformed theories, including those with the more
general twist, were shown to have retained their integrable structure. Here we
examine the Yangian algebra of these deformed theories. In a five field
subsector, we compute the two cases of SU(2)xU(1)xU(1)xU(1) and
SU(2|1)xU(1)xU(1) as residual symmetries of SU(2,2|1)xU(1)xU(1). We compute a
twisted coproduct for these theories, and show that only for the residual
symmetry do we retain the standard coproduct. The twisted coproduct thus
provides a method for symmetry breaking. However, the full Yangian structure of
SU(2|3) is manifest in our subsector, albeit with twisted coproducts, and
provides for the integrability of the theory.Comment: 17 page
Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of Euclidean Gravity: Diffeomorphism Covariance
The G-->0 limit of Euclidean gravity introduced by Smolin is described by a
generally covariant U(1)xU(1)xU(1) gauge theory. In an earlier paper, Tomlin
and Varadarajan constructed the quantum Hamiltonian constraint of density
weight 4/3 for this U(1)xU(1)xU(1) theory so as to produce a non-trivial
anomaly free LQG-type representation of the Poisson bracket between a pair of
Hamiltonian constraints. These constructions involved a choice of regulating
coordinate patches. The use of these coordinate patches is in apparent conflict
with spatial diffeomorphism covariance. In this work we show how an appropriate
choice of coordinate patches together with suitable modifications of these
constructions results in the diffeomorphism covariance of the continuum limit
action of the Hamiltonian constraint operator, while preserving the anomaly
free property of the continuum limit action of its commutator.Comment: 56 pages, No figure
D-brane Black Holes: Large-N Limit and the Effective String Description
We address the derivation of the effective conformal field theory description
of the 5-dimensional black hole, modelled by a collection of D1- and D5-
branes, from the corresponding low energy U(Q_1)xU(Q_5) gauge theory. Finite
horizon size at weak coupling requires both Q_1 and Q_5 to be large. We derive
the result in the moduli space approximation (say for Q_1>Q_5) and appeal to
supersymmetry to argue its validity beyond weak coupling. As a result of a
combination of quenched Z_{Q_1} Wilson lines and a residual Weyl symmetry, the
low-lying excitations of the U(Q_1)xU(Q_5) gauge theory are described by an
effective N=4 superconformal field theory with c=6 in 1+1 dimensions, where the
space is a circle of radius RQ_1Q_5. We also discuss the appearance of a
marginal perturbation of the effective conformal field theory for large but
finite values of Q_5.Comment: 15 pages, LaTeX, some comments added to make the arguments in
sections 4 and 5 more precise, to appear in Phys. Lett.
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