Abstract:
We generalize the method of regularized traces which calculates eigenvalues of a perturbed discrete operator for the case of an arbitrary multiplicity of eigenvalues of the unperturbed operator. We obtain a system of equations, enabling one to calculate eigenvalues of the perturbed operator with large ordinal numbers. As an example, we calculate eigenvalues of a perturbed Laplace operator in a rectangle.
Keywords:a discrete self-adjoint operator, a separable Hilbert space, eigenvalues and eigenfunctions of an operator, a regularized trace, errors in the perturbation theory.