Extremal Black Holes as Bound States

We consider a simple static extremal multi-black hole solution with constituents charged under different $U(1)$ fields. Each of the constituents by itself is an extremal dilatonic black hole of coupling a=\srt. For a special case with two electrically and two magnetically charged black holes the multi-black hole solution interpolates between the familiar $a=\sqrt{3},1,\frac{1}{\sqrt{3}}$ and $0$ solutions, depending on how many black holes are placed at infinity. This proves the hypothesis that black holes with the above dilaton couplings arise in string theory as bound states of fundamental $a=\sqrt{3}$ states with zero binding energy. We also generalize the result to states where the action does not admit a single scalar truncation and show that a wide class of dyonic black holes in toroidally compactified string theory can be viewed as bound states of fundamental a=\srt black holes.Comment: 9 pages, LaTex, to appear in PLB, references adde

Near Horizon Superspace

The adS_{p+2} x S^{d-p-2} geometry of the near horizon branes is promoted to a supergeometry: the solution of the supergravity constraints for the vielbein, connection and form superfields are found. This supergeometry can be used for the construction of new superconformal theories. We also discuss the Green-Schwarz action for a type IIB string on adS_5 x S_5.Comment: 11 pages, LaTe

The GS String Action on AdS_5 x S^5

We present a simple form of the Type IIB string action on $AdS_5\times S^5$. The result is achieved by fixing $\kappa$-symmetry in the Killing spinor gauge defined by the projector of the Killing spinor of the D3 brane. We show explicitly that in this gauge the superspace is greatly simplified which is the crucial ingredient for the simple string action.Comment: LaTex, 8 page

Holography in Superspace

The AdS/CFT correspondence identifies the coordinates of the conformal boundary of anti-de Sitter space with the coordinates of the conformal field theory. We generalize this identification to theories formulated in superspace. As an application of our results, we study a class of Wilson loops in N=4 SYM theory. A gauge theory computation shows that the expectation values of these loops are invariant under a local kappa-symmetry, except at intersections. We identify this with the kappa-invariance of the associated string worldsheets in the corresponding bulk superspace.Comment: 36 pages, LaTeX, references adde

A Construction of Killing Spinors on S^n

We derive simple general expressions for the explicit Killing spinors on the n-sphere, for arbitrary n. Using these results we also construct the Killing spinors on various AdS x Sphere supergravity backgrounds, including AdS_5 x S^5$, AdS_4 x S^7 and AdS_7 x S^4. In addition, we extend previous results to obtain the Killing spinors on the hyperbolic spaces H^n.Comment: 11 pages, LaTe

Supersymmetry and Dual String Solitons

We present new classes of string-like soliton solutions in ($N=1$; $D=10$), ($N=2$; $D=6$) and ($N=4$; $D=4$) heterotic string theory. Connections are made between the solution-generating subgroup of the $T$-duality group of the compactification and the number of spacetime supersymmetries broken. Analogous solutions are also noted in ($N=1,2$; $D=4$) compactifications, where a different form of supersymmetry breaking arises.Comment: 13 pages, harvmac, (missing references added

A Simple Particle Action from a Twistor Parametrization of AdS_5

The SO(4,2) isometries of AdS_5 are realized non-linearly on its horospherical coordinates (x^m,\rho). On the other hand, Penrose twistors have long been known to linearly realize these symmetries on 4-dimensional Minkowski space, the boundary of AdS_5, parametrized by x^m. Here we extend the twistor construction and define a pair of twistors, allowing us to include a radial coordinate in the construction. The linear action of SO(4,2) on the twistors induces the correct isometries of AdS_5. We apply this new construction to the study of the dynamics of a massive particle in AdS_5. We show that in terms of the twistor variables the action takes a simple form of a 1-dimensional gauge theory. Our result might open up the possibility to find a simple worldvolume action also for the string propagating on AdS_5.Comment: 11 pages, LaTe

D1 and D5-Brane Actions in AdS_m x S^n

The kappa-invariant and supersymmetric actions of D1 and D5-branes in AdS_3 x S^3 are investigated, as well as the action of a D5-brane in an AdS_5 x S^5 background. The action of a D5-brane lying totally in an AdS_3 x S^3 background is found. Some progress was made towards finding the action for the D5-brane free to move in the whole AdS_3 x S^3 x T^4 space, however the supersymmetric action found here is not kappa-invariant and the reasons the method used did not find a kappa-invariant solution are discussed.Comment: 17pp, Latex, improved explanations, a definition adde