Huygens' Principle in Minkowski Spaces and Soliton Solutions of the Korteweg-de Vries Equation

A new class of linear second order hyperbolic partial differential operators satisfying Huygens' principle in Minkowski spaces is presented. The construction reveals a direct connection between Huygens' principle and the theory of solitary wave solutions of the Korteweg-de Vries equation.Comment: 23 pages, LaTeX, to be published in Comm.Math.Phys (1997