Computable bounds for eigenvalues and eigenfunctions of elliptic differential operators
Given an approximate eigenfunction for a self-adjoint operator not necessarily lying in its domain, bounds for an eigenvalue and eigenfunction are given. The method is applied to the L-shaped membrane. Some of the results were published twenty years ago and a search of the scientific citation index (or of the Zentralblatt (MATH database)) would have yielded some of these omitted references.
scientific article; zbMATH DE number 4082898
scientific article