O(d, d)-Symmetry and Ernst Formulation for Einstein-Kalb-Ramond Theory   in Two Dimensions
  The (3+d)-dimensional Einstein-Kalb-Ramond theory reduced to two dimensions is considered. It is shown that the theory allows two different Ernst-like $d \times d$ matrix formulations: the real non-dualized target space and the Hermitian dualized non-target space ones. The O(d, d) symmetry is written in a SL(2,R) matrix-valued form in both cases. The Kramer-Neugebauer transformation, which algebraically maps the non-dualized Ernst potential into the dualized one, is presented. 
A. Herrera and O. Kechkin