A singular characteristic boundary value problem for the Euler-Poisson-Darboux equation

Summary The paper considers a singular characteristic boundary value problem for the well known EPD equation. By using a modified Riemann method, a formula is obtained which is shown to provide a weak solution of the problem. The weak solution is then shown to be a solution in the classical sense by investigating its differentiability properties. The research of the second author has been supported by NSF research grant GP-11543. Entrata in Redazione il 10 novembre 1971.