Johannes Brasche, Mark M. Malamud, Hagen Neidhardt
Weyl function and spectral properties of self-adjoint extensions
(340K, postscript)

ABSTRACT.  We characterize the spectra of self-adjoint extensions of a symmetric 
operator with equal deficiency indices in terms of boundary values of 
their Weyl functions. A complete description is obtained for the point 
and absolutely continuous spectrum while for the singular continuous 
spectrum additional assumptions are needed. The results are illustrated 
by examples.