Intersecting M-branes as Four-Dimensional Black Holes

We present two 1/8 supersymmetric intersecting p-brane solutions of 11-dimensional supergravity which upon compactification to four dimensions reduce to extremal dyonic black holes with finite area of horizon. The first solution is a configuration of three intersecting 5-branes with an extra momentum flow along the common string. The second describes a system of two 2-branes and two 5-branes. Related (by compactification and T-duality) solution of type IIB theory corresponds to a completely symmetric configuration of four intersecting 3-branes. We suggest methods for counting the BPS degeneracy of three intersecting 5-branes which, in the macroscopic limit, reproduce the Bekenstein-Hawking entropy.Comment: 15 pages, harvmac; a reference added (the version to appear in Nulcear Physics B

String Tensions and Three Dimensional Confining Gauge Theories

In the context of gauge/gravity duality, we try to understand better the proposed duality between the fractional D2-brane supergravity solutions of (Nucl. Phys. B 606 (2001) 18, hep-th/0101096) and a confining 2+1 dimensional gauge theory. Based on the similarities between this fractional D2-brane solution and D3-brane supergravity solutions with more firmly established gauge theory duals, we conjecture that a confining q-string in the 2+1 dimensional gauge theory is dual to a wrapped D4-brane. In particular, the D4-brane looks like a string in the gauge theory directions but wraps a S**3 in S**4 in the transverse geometry. For one of the supergravity solutions, we find a near quadratic scaling law for the tension: $T \sim q (N-q)$. Based on the tension, we conjecture that the gauge theory dual is SU(N) far in the infrared. We also conjecture that a quadratic or near quadratic scaling is a generic feature of confining 2+1 dimensional SU(N) gauge theories.Comment: 23 pages, 2 figure

Non-Singularity of the Exact Two-Dimensional String Black Hole

We study the global structure of the exact two-dimensional space-time which emerges from string theory. Previous work has shown that in the semi-classical limit, this is a black hole similar to the Schwarzschild solution. However, we find that in the exact case, a new Euclidean region appears "between" the singularity and black hole interior. However the boundary between the Lorentzian and Euclidean regions is a coordinate singularity, which turns out to be a surface of time reflection symmetry in an extended space-time. Thus strings having fallen through the black hole horizon would eventually emerge through another one into a new asymptotically flat region. The maximally extended space-time consists of an infinite number of universes connected by wormholes. There are no singularities present in this geometry. We also calculate the mass and temperature associated with the space-time.Comment: 9 pages, latex, DAMTP R93/

Black Hole Graybody Factor and Black Hole Entropy

We have proposed the entropy formula of the black hole which is constructed by the intersecting D1-brane and D5-brane with no momentum, whose compactification radii are constrained by the surface gravities in ten-dimensions. We interpret the entropy of the black hole as the statistical entropy of the effective string living on the D5-brane. We further study the behavior of the absorption cross-section of the black hole using our entropy formula.Comment: 15 pages, RevTex, version to appear in PR

Moduli Instability in Warped Compactifications of the Type IIB Supergravity

We show that the conifold and deformed-conifold warped compactifications of the ten-dimensional type IIB supergravity, including the Klebanov-Strassler solution, are dynamically unstable in the moduli sector representing the scale of a Calabi-Yau space, although it can be practically stable for a quite long time in a region with a large warp factor. This instability is associated with complete supersymmetry breaking except for a special case and produces significant time-dependence in the structure of the four-dimensional base spacetime as well as of the internal space.Comment: 24 pages, no figure. Typos corrected, and some arguments in section 5 are adde

Absorption of Fixed scalars and the D-brane Approach to Black Holes

We calculate the emission and absorption rates of fixed scalars by the near-extremal five-dimensional black holes that have recently been modeled using intersecting D-branes. We find agreement between the semi-classical and D-brane computations. At low energies the fixed scalar absorption cross-section is smaller than for ordinary scalars and depends on other properties of the black hole than just the horizon area. In the D-brane description, fixed scalar absorption is suppressed because these scalars must split into at least four, rather than two, open strings running along the D-brane. Consequently, this comparison provides a more sensitive test of the effective string picture of the D-brane bound state than does the cross-section for ordinary scalars. In particular, it allows us to read off the value of the effective string tension. That value is precisely what is needed to reproduce the near-extremal 5-brane entropy.Comment: 33 pages, harvmac, version to appear in Nucl. Phys.

Entropy of Near-Extremal Black p-branes

We carry out a thorough survey of entropy for a large class of $p$-branes in various dimensions. We find that the Bekenstein-Hawking entropy may be given a simple world volume interpretation only for the non-dilatonic $p$-branes, those with the dilaton constant throughout spacetime. The entropy of extremal non-dilatonic $p$-branes is non-vanishing only for the solutions preserving 1/8 of the original supersymmetries. Upon toroidal compactification these reduce to dyonic black holes in 4 and 5 dimensions. For the self-dual string in 6 dimensions, which preserves 1/4 of the original supersymmetries, the near-extremal entropy is found to agree with a world sheet calculation, in support of the existing literature. The remaining 3 interesting cases preserve 1/2 of the original supersymmetries. These are the self-dual 3-brane in 10 dimensions, and the 2- and 5-branes in 11 dimensions. For all of them the scaling of the near-extremal Bekenstein-Hawking entropy with the Hawking temperature is in agreement with a statistical description in terms of free massless fields on the world volume.Comment: 16 pages, harvmac; improved discussion of M-theory charge quantization (version to appear in Nucl. Phys. B

Curvature Dependence of Running Gauge Coupling and Confinement in AdS/CFT Correspondence

We construct IIB supergravity (viewed as dilatonic gravity) background with non-trivial dilaton and with curved four-dimensional space. Such a background may describe another vacuum of maximally supersymmetric Yang-Mills theory or strong coupling regime of (non)-supersymmetric gauge theory with (power-like) running gauge coupling which depends on curvature. Curvature dependent quark-antiquark potential is calculated where the geometry type of hyperbolic (or de Sitter universe) shows (or not) the tendency of the confinement. Generalization of IIB supergravity background with non-constant axion is presented. Quark-antiquark potential being again curvature-dependent has a possibility to produce the standard area law for large separations.Comment: LaTeX file, 24 pages, presentation is improve

Multi-Trace Operators and the Generalized AdS/CFT Prescription

We show that multi-trace interactions can be consistently incorporated into an extended AdS/CFT prescription involving the inclusion of generalized boundary conditions and a modified Legendre transform prescription. We find new and consistent results by considering a self-contained formulation which relates the quantization of the bulk theory to the AdS/CFT correspondence and the perturbation at the boundary by double-trace interactions. We show that there exist particular double-trace perturbations for which irregular modes are allowed to propagate as well as the regular ones. We perform a detailed analysis of many different possible situations, for both minimally and non-minimally coupled cases. In all situations, we make use of a new constraint which is found by requiring consistence. In the particular non-minimally coupled case, the natural extension of the Gibbons-Hawking surface term is generated.Comment: 27 pages, LaTeX, v.2:minor changes, v.3:comments added, v.4:several new results, discussions, references and a section of Conclusions added. Previous results unchanged, v.5: minor changes. Final version to be published in Phys.Rev.

Winding Strings and Decay of D-Branes with Flux

We study the boundary state associated with the decay of an unstable D-brane with uniform electric field, 1>e>0 in the string units. Compactifying the D-brane along the direction of the electric field, we find that the decay process is dominated by production of closed strings with some winding numbers; closed strings produced are such that the winding mode carries precisely the fraction $e$ of the individual string energy. This supports the conjecture that the final state at tree level is composed of winding strings with heavy oscillations turned on. As a corollary, we argue that the closed strings disperse into spacetime at a much slower rate than the case without electric field.Comment: 14 pages, harvmac, minor changes, clarified gauge choice, version to appear in JHE