A Charged Rotating Black Ring

We construct a supergravity solution describing a charged rotating black ring with S^2xS^1 horizon in a five dimensional asymptotically flat spacetime. In the neutral limit the solution is the rotating black ring recently found by Emparan and Reall. We determine the exact value of the lower bound on J^2/M^3, where J is the angular momentum and M the mass; the black ring saturating this bound has maximum entropy for the given mass. The charged black ring is characterized by mass M, angular momentum J, and electric charge Q, and it also carries local fundamental string charge. The electric charge distributed uniformly along the ring helps support the ring against its gravitational self-attraction, so that J^2/M^3 can be made arbitrarily small while Q/M remains finite. The charged black ring has an extremal limit in which the horizon coincides with the singularity.Comment: 25 pages, 1 figur

Thermodynamics of charged and rotating black strings

We study thermodynamics of cylindrically symmetric black holes. Uncharged as well as charged and rotating objects have been discussed. We derive surface gravity and hence the Hawking temperature and entropy for all these cases. We correct some results in the literature and present new ones. It is seen that thermodynamically these black configurations behave differently from spherically symmetric objects

Marginal Deformations of WZNW and Coset Models from O(d,d) Transformation

We show that O(2,2) transformation of SU(2) WZNW model gives rise to marginal deformation of this model by the operator $\int d^2 z J(z)\bar J(\bar z)$ where $J$, $\bar J$ are U(1) currents in the Cartan subalgebra. Generalization of this result to other WZNW theories is discussed. We also consider O(3,3) transformation of the product of an SU(2) WZNW model and a gauged SU(2) WZNW model. The three parameter set of models obtained after the transformation is shown to be the result of first deforming the product of two SU(2) WZNW theories by marginal operators of the form $\sum_{i,j=1}^2 C_{ij} J_i \bar J_j$, and then gauging an appropriate U(1) subgroup of the theory. Our analysis leads to a general conjecture that O(d,d) transformation of any WZNW model corresponds to marginal deformation of the WZNW theory by combination of appropriate left and right moving currents belonging to the Cartan subalgebra; and O(d,d) transformation of a gauged WZNW model can be identified to the gauged version of such marginally deformed WZNW models.Comment: 26 pages, phyzzx.tex, TIFR-TH-92-6

Rotating Black Holes which Saturate a Bogomol'nyi Bound

We construct and study the electrically charged, rotating black hole solution in heterotic string theory compactified on a $(10-D)$ dimensional torus. This black hole is characterized by its mass, angular momentum, and a $(36-2D)$ dimensional electric charge vector. One of the novel features of this solution is that for $D >5$, its extremal limit saturates the Bogomol'nyi bound. This is in contrast with the $D=4$ case where the rotating black hole solution develops a naked singularity before the Bogomol'nyi bound is reached. The extremal black holes can be superposed, and by taking a periodic array in $D>5$, one obtains effectively four dimensional solutions without naked singularities.Comment: 13 pages, no figure

Black Rings, Supertubes, and a Stringy Resolution of Black Hole Non-Uniqueness

In order to address the issues raised by the recent discovery of non-uniqueness of black holes in five dimensions, we construct a solution of string theory at low energies describing a five-dimensional spinning black ring with three charges that can be interpreted as D1-brane, D5-brane, and momentum charges. The solution possesses closed timelike curves (CTCs) and other pathologies, whose origin we clarify. These pathologies can be avoided by setting any one of the charges, e.g. the momentum, to zero. We argue that the D1-D5-charged black ring, lifted to six dimensions, describes the thermal excitation of a supersymmetric D1-D5 supertube, which is in the same U-duality class as the D0-F1 supertube. We explain how the stringy microscopic description of the D1-D5 system distinguishes between a spherical black hole and a black ring with the same asymptotic charges, and therefore provides a (partial) resolution of the non-uniqueness of black holes in five dimensions.Comment: 33 pages, 1 figur

On Some New Black String Solutions in Three Dimensions

We derive several new solutions in three-dimensional stringy gravity. The solutions are obtained with the help of string duality transformations. They represent stationary configurations with horizons, and are surrounded by (quasi) topologically massive Abelian gauge hair, in addition to the dilaton and the Kalb-Ramond axion. Our analysis suggests that there exists a more general family, where our solutions are special limits. Finally, we use the generating technique recently proposed by Garfinkle to construct a traveling wave on the extremal variant of one of our solutions.Comment: revtex, 38 pages including 3 figure