CONFORMALLY EXACT RESULTS FOR SL(2, R)CIRCLE-TIMES-SO(1, 1)D-2/SO(1, 1) COSET MODELS

Using the conformal invariance of the SL(2,R) x 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) x R(d-2) for the vector gauging and (3d black string) x R(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 Home and Horowitz. If the value of k is finite we find two curvature singularities which degenerate to one in the semi-classical k --> infinity 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.