results on the rates of convergence or metastability (in the sense of T. Tao). E.g. using this approach we get a simple proof … metastability. If A has a modulus of regularity w.r.t. zerA\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage … (without any compactness or regularity assumption) and give a rate of metastability. …