M. Kraus, M. Langer and C. Tretter,
Variational principles and eigenvalue estimates for unbounded
block operator matrices and applications,
J. Comput. Appl. Math. 171 (2004), 311–334
Abstract:
In this paper we establish variational principles, eigenvalue estimates and
asymptotic formulae for eigenvalues of three different classes of
unbounded block operator matrices. The results allow to characterise eigenvalues
that are not necessarily located at the boundary of the spectrum.
Applications to an example from magnetohydrodynamics and to
Dirac operators on certain manifolds are given.