We give the explicit expression for four-dimensional rotating charged black hole solutions of N = 4 (or N = 8) superstring vacua, parameterized by the ADM mass, four charges (two electric and two magnetic charges, each arising from a different U (1) gauge factors), and the angular momentum (as well as the asymptotic values of four toroidal moduli of two-torus and the dilatonaxion field). The explicit form of the thermodynamic entropy is parameterized in a suggestive way as a sum of the product of the 'left-moving' and the 'rightmoving' terms, which may have an interpretation in terms of the microscopic degrees of freedom of the corresponding D-brane configuration. We also give an analogous parameterization of the thermodynamic entropy for the recently obtained five-dimensional rotating charged black holes parameterized by the ADM mass, three U (1) charges and two rotational parameters (as well as the asymptotic values of one toroidal modulus and the dilaton).

We present the most general rotating black hole solution of five-dimensional N = 4 superstring vacua that conforms to the "no hair theorem". It is chosen to be parameterized in terms of massless fields of the toroidally compactified heterotic string. The solutions are obtained by performing a subset of O(8, 24) transformations, i.e., symmetry transformations of the effective three-dimensional action for stationary solutions, on the five-dimensional (neutral) rotating solution parameterized by the mass m and two rotational parameters l 1 and l 2 . The explicit form of the generating solution is determined by three SO(1, 1) ⊂ O(8, 24) boosts, which specify two electric charges Q(1) 1 , Q(2) 2 of the Kaluza-Klein and two-form U (1) gauge fields associated with the same compactified direction, and the charge Q (electric charge of the vector field, whose field strength is dual to the field strength of the five-dimensional two-form field). The general solution, parameterized by 27 charges, two rotational parameters and the ADM mass compatible with the Bogomol'nyi bound, is obtained by imposing [SO(5) × SO(21)]/[SO(4) × SO(20)] ⊂ O(5, 21) transformations, which do not affect the five-dimensional space-time. We also analyze the deviations from the BPS-saturated limit.

Within effective heterotic superstring theory compactified on a six-torus we derive minimum energy (supersymmetric), static, spherically symmetric solutions, which are manifestly invariant under the target space O(6, 22) and the strong-weak coupling SL(2) duality symmetries with 28 electric and 28 magnetic charges subject to one constraint. The class of solutions with a constant axion corresponds to dyonic configurations subject to two charge constraints, with purely electric [or purely magnetic] and dyonic configurations preserving 1 2 and 1 4 of N = 4 supersymmetry, respectively. General dyonic configurations in this class have a space-time of extreme Reissner-Nordström black holes while configurations with more constrained charges have a null or a naked singularity.

We study vacuum domain walls in a class of four-dimensional N = 1 supergravity theories where along with the matter field, forming the wall, there is more than one "dilaton," each respecting SU(1,l) symmetry in their subsector. We find supersymmetric (planar, static) walls, interpolating between a Minkowski vacuum and a new class of supersymmetric vacua which have a naked (planar) singularity. Although such walls correspond to idealized configurations, i.e., they correspond to planar configurations of infinite extent, they provide the first example of supersymmetric classical solitons with naked singularities.PACS number(s): 04.20.Dw, 04.65.+e, 11.27.+d Some of the solutions of gravity theory correspond to configurations with naked space-time singularities, i.e., singularities which are not hidden behind horizons. This uncomfortable feature is remedied by Penrose's conjecture, which states that generic initial conditions do not evolve to form naked singularities [I]. Such a conjecture is difficult to prove, and the dynamical formation of naked singularities has been addressed only for specific cases [2].On the other hand, it has been observed [3-51 that in supersymmetric theories the allowed black hole configurations are only those with mass M bounded from below by the Bogomol'nyi bound, e.g., M 2 d m , where

We present the most general static, spherically symmetric solutions of heterotic string compactified on a six-torus that conforms to the conjectured "no-hair theorem", by performing a subset of O(8, 24) transformations, i.e., symmetry transformations of the effective three-dimensional action for stationary solutions, on the Schwarzschild solution. The explicit form of the generating solution is determined by six SO(1, 1) ⊂ O(8, 24) boosts, with the zero Taub-NUT charge constraint imposing one constraint among two boost parameters. The non-nontrivial scalar fields are the axion-dilaton field and the moduli of the two-torus. The general solution, parameterized by unconstrained 28 magnetic and 28 electric charges and the ADM mass compatible with the Bogomol'nyi bound, is obtained by imposing on the generating solution [SO(6) × SO (22)]/[SO(4) × SO(20)] ⊂ O(6, 22) (T -duality) transformation and SO(2) ⊂ SL(2, R) (S-duality) transformation, which do not affect the four-dimensional space-time. Depending on the range of boost parameters, the non-extreme solutions have the space-time of either Schwarzschild or Reissner-Nordström black hole, while extreme ones have either null (or naked) singularity, or the space-time of extreme Reissner-Nordström black hole.