A strong comparison theorem for selfadjoint elliptic equations
Kurt Kreith · Proceedings of the American Mathematical Society · 1968
The purpose of this note is to give a concise proof of a comparison theorem for selfadjoint, second order elliptic equations which yields stronger results than those previously derived in [1], [2] and [3]. All coefficients and domains are to be sufficiently smooth so that the variational techniques of Courant [4] can be applied. Specifically, it is assumed that the first eigenfunction of the selfadjoint boundary value problem