Delta-like singularity in the Radial Laplace Operator and the Status of   the Radial Schrodinger Equation
  By careful exploration of separation of variables into the Laplacian in spherical coordinates, we obtain the extra delta-like singularity, elimination of which restricts the radial wave function at the origin. This constraint has the form of boundary condition for the radial Schrodinger equation. 
Anzor A.Khelashvili and Teimuraz P. Nadareishvili
math-ph math.MP quant-ph