  Quasidiagonal operators on a Hilbert space are a large and important class
(containing all self-adjoint operators for instance). They are also perfectly
suited for study via the finite section method (a particular Galerkin method).
Indeed, the very definition of quasidiagonality yields finite sections with
good convergence properties. Moreover, simple operator theory techniques yield
estimates on certain rates of convergence. In the case of quasidiagonal band
operators both the finite sections and rates of convergence are explicitly
given.
