Conformally Exact Results For

Using the conformal invariance of the SL(2, IR) ⊗ SO(1, 1) d−2 /SO(1, 1) coset models we calculate the conformally exact metric and dilaton, to all orders in the 1/k expansion. We consider both vector and axial gauging. We find that these cosets represent two different space–time geometries: (2d black hole)⊗IR d−2 for the vector gauging and (3d black string)⊗IR d−3 for the axial one. In particular for d = 3 and for the axial gauging one obtains the exact metric and dilaton of the charged black string model introduced by Horne and Horowitz. If the value of k is finite we find two curvature singularities which degenerate to one in the semi–classical k → ∞ limit. We also calculate the reflection and transmission coefficients for the scattering of a tachyon wave and using the Bogoliubov transformation we find the Hawking temperature.