In this note we give a short and self-contained proof for a criterion of Eidelheit on the solvability of linear equations in infinitely many variables. We use this criterion to study the surjectivity of magnetic Schrödinger operators on bundles over graphs.

We study expectation values of matrix elements for boundary values of the resolvent as well as the density of states for a random Schrödinger operator with potential distributed according to a Poisson process. Asymptotic expansions for these quantities in the limit of small disorder are derived. Explicit estimates for the expansion coefficients are given and we show that their infinite volume limits are in fact finite as the spectral parameter approaches the spectrum of the free Laplacian.

No abstract