Spectral Theory, Microlocal Analysis, Singular Manifolds

The spectral theory of differential operators is a challenging subject with deep connections to many branches of mathematics and mathematical physics. It is a central issue in this volume. The first contribution addresses domain perturbations for generalized Schroedinger operators and the influence of the capacity on spectral data. There follows an article discussing the minimal smoothness assumptions on the domain under which the asymptotics of the counting function for the eigenvalues of elliptic boundary value problems can be determined. Systems of h-pseudo-differential operators on the half-line are studied in the next paper. The results concern existence and distribution of resonances for various semi-classical regimes. Three further articles are devoted to the regularity and symptotics of solutions to partial differential equations on singular manifolds. A very efficient tool is the combination of suitable operator algebras and pseudo-differential calculi with sufficiently rich symbolic structures. One paper considers the case of manifolds with non-compact ends, another the case of higher cuspidal singularities. A final contribution treats degenerate hyperbolic equations.