Two-sided approximation of eigenvalues of some elliptic operators (Q2387978)

For various kinds of eigenvalue problems for elliptic second-order partial differential equations with zero normal boundary conditions on the rectangle error estimations are developed. It is shown how to construct the discrete analogy of the approximation process with increased accuracy. Using the asymptotic error estimates the author constructs discrete problems whose eigenvalues approach the corresponding eigenvalues of the original problem from different sides.