Matrix Ernst potentials for Einstein-Maxwell-dilaton-axion with multiple vector fields

We show that the Einstein-Maxwell-dilaton-axion system with multiple vector fields (bosonic sector of the D = 4, N = 4 supergravity) restricted to spacetimes possessing a non-null Killing vector field admits a concise representation in terms of the Ernst-type matrix valued potentials. A constructive derivation of the SWIP solutions is given and a colliding waves counterpart of the DARN-NUT solution is obtained. SU(m,m) chiral representation of the two-dimensionally reduced system is derived and the corresponding Kramer-Neugebauer-type map is presented. (C) 1997 Published by Elsevier Science B.V.