The Two-Parameter Brane Sigma-Model: M*, M' solutions and M-theory   solutions dependent on exotic coordinates
  We investigate two-parameter solutions of sigma-models on two dimensional symmetric spaces contained in E11. Embedding such sigma-model solutions in space-time gives solutions of M* and M'-theory where the metric depends on general travelling wave functions, as opposed to harmonic functions typical in general relativity, supergravity and M-theory. Weyl reflection allows such solutions to be mapped to M-theory solutions where the wave functions depend explicitly on extra coordinates contained in the fundamental representation of E11. 
Paul P. Cook and Sarben Sarkar
hep-th