  In a recent article, Arendt and ter Elst have shown that every sectorial form
is in a natural way associated with the generator of an analytic strongly
continuous semigroup, even if the form fails to be closable. As an intermediate
step they have introduced so-called j-elliptic forms, which generalises the
concept of elliptic forms in the sense of Lions. We push their analysis forward
in that we discuss some perturbation and convergence results for semigroups
associated with j-elliptic forms. In particular, we study convergence with
respect to the trace norm or other Schatten norms. We apply our results to
Laplace operators and Dirichlet-to-Neumann-type operators.
