Quasi-unitary equivalence and generalised norm resolvent convergence

Abstract

The purpose of this article is to give a short introduction to the concept of quasi-unitary equivalence of quadratic forms and its consequences. In particular, we improve an estimate concerning the transitivity of quasi-unitary equivalence for forms. We illustrate the abstract setting by two classes of examples.

20 pages, this is a submission of an already published article, reference list is as at time of publication