Supergravity Solutions for Localized Intersections of Branes

We construct an explicit supergravity solution for a configuration of localized D4-brane ending on a D6-brane, restricted to the near horizon region of the latter. We generate this solution by dimensionally reducing the supergravity solution for a flat M5-brane in $R^{1,7} \times C^2/Z_N$ with the M5-brane partially embedded in $C^2/Z_N$. We describe the general class of localized intersections and overlaps whose supergravity solutions are constructible in this way.Comment: 15 pages, 1 figur

On the Hierarchy Between Non-Commutative and Ordinary Supersymmetric Yang-Mills

Non-commutative supersymmetric Yang-Mills with rational Theta is dual to an ordinary supersymmetric Yang-Mills with a 't Hooft flux. It is believed that the simplest description is via the ordinary supersymmetric Yang-Mills. We claim, however, that the two descriptions form a hierarchy. The SYM description is the proper description in the ultra violet while the non-commutative description takes over in the infra red.Comment: 16 pages, 3 figures, references adde

Perturbative Dynamics of Fractional Strings on Multiply Wound D-strings

Fractional strings in the spectrum of states of open strings attached to a multiply wound D-brane is explained. We first describe the fractional string states in the low-energy effective theory where the topology of multiple winding is encoded in the gauge holonomy. The holonomy induces twisted boundary conditions responsible for the fractional moding of these states. We also describe fractional strings in world sheet formulation and compute simple scattering amplitudes for Hawking emission/absorption. Generalization to fractional DN-strings in a 1-brane 5-brane bound state is described. When a 1-brane and a 5-brane wraps $Q_1$ and $Q_5$ times respectively around a circle, the momentum of DN-strings is quantized in units of $2 \pi/L Q_1 Q_5$. These fractional states appear naturally in the perturbative spectrum of the theory.Comment: 14 pages, LaTeX, 3 figure

Matrix Model Approach to d>2d>2 Non-critical Superstrings

We apply light-cone quantization to a $1+1$ dimensional supersymmetric field theory of large N matrices. We provide some preliminary numerical evidence that when the coupling constant is tuned to a critical value, this model describes a 2+1 dimensional non-critical superstring.Comment: 11 pages, 3 Encapsulated Postscript figures. uses psfig.sty (available from http://xxx.lanl.gov/ftp/hep-th/papers/macros

Large branes in AdS and their field theory dual

Recently it was suggested that a graviton in $AdS_5 \times S^5$ with a large momentum along the sphere can blow up into a spherical D-brane in $S^5$. In this paper we show that the same graviton can also blow up into a spherical D-brane in $AdS_5$ with exactly the same quantum numbers (angular momentum and energy). These branes are BPS, preserving 16 of the 32 supersymmetries. We show that there is a BPS {\it classical} solution for SYM on $S^3\times R$ with exactly the same quantum numbers. The solution has non-vanishing Higgs expectation values and hence is dual to the large brane in AdS.Comment: 20 pages, 6 figures, minor change

Dynamics of N=4{\cal N}=4 supersymmetric field theories in 2+1 dimensions and their gravity dual

In this note we consider ${\cal N}=4$ SYM theories in 2+1 dimensions with gauge group $U(N)\times U(M)$ and $k$ hypermultiplets charged under the $U(N)$. When $k > 2(N-M)$, the theory flows to a superconformal fixed point in the IR. Theories with $k <2(N-M)$, on the other hand, flows to strong coupling. We explore these theories from the perspective of gravity dual. We find that the gravity duals of theories with $k < (N-M)$ contain enhancons even in situations where repulson singularities are absent. We argue that supergravity description is unreliable in the region near these enhancon points. Instead, we show how to construct reliable sugra duals to particular points on the Coulomb branch where the enhancon is screened. We explore how these singularities reappear as one moves around in Coulomb branch and comment on possible field theory interpretation of this phenomenon. In analyzing gauge/gravity duality for these models, we encountered one unexpected surprise, that the condition for the supergravity solution to be reliable and supersymmetric is somewhat weaker than the expectation from field theory. We also discuss similar issues for theories with $k=0$.Comment: 31 pages, 12 figure