|Date:||Wed, October 26, 2011|
|Place:||Research I Seminar room|
Abstract: The Bourgain-Tzafriri Restricted Invertibility Theorem states conditions under which a Riesz bases (with controlled lower Riesz bound) can be extracted from a possibly overcomplete system of vectors in finite dimensional spaces. A recent algorithm of Spielman and Srivastava allow optimal control of the lower Riesz bound. We shall show how to modify their algorithm in order to control the upper Riesz bound as well.