© Hindawi Publishing Corp. HARMONICITY OF HORIZONTALLY CONFORMAL MAPS AND SPECTRUM OF THE LAPLACIAN

We discuss the harmonicity of horizontally conformal maps and their relations with the spectrum of the Laplacian. We prove that if φ: M → N is a horizontally conformal map such that the tension field is divergence free, then φ is harmonic. Furthermore, if N is noncompact, then φ must be constant. Also we show that the projection of a warped product manifold onto the first component is harmonic if and only if the warping function is constant. Finally, we describe a characterization for a horizontally conformal map with a constant dilation preserving an eigenfunction. 2000 Mathematics Subject Classification: 53C43, 58E20, 58C40. 1. Introduction. Th