| The first part of the present work is devoted to give upper estimates for the distance from an operator to the set of the essentially G;In the later part, the notion of the intermediate orbit of an operator is studied. In the case of a compact operator, the closure of the intermediate orbit coincides with the closure of the similarity orbit. It is also shown that the closure of the intermediate orbit, for some essentially normal operators with no index obstruction, always contains a normal operator. |
