Harmonic morphisms between degenerate semi-Riemannian manifolds
arXiv:math/0303275
Abstract
In this paper we generalize harmonic maps and morphisms to the \emph{degenerate semi-Riemannian category}, in the case when the manifolds and are \emph{stationary} and the map is \emph{radical-preserving}. We characterize geometrically the notion of \emph{(generalized) horizontal (weak) conformality} and we obtain a characterization for (generalized) harmonic morphisms in terms of (generalized) harmonic maps.
21 pages, LaTeX