Analysis Seminar: "Remarks on Essential Codimension"
Abstract: In 1973, Brown, Douglas and Fillmore introduced the notion of essential codimension of projections, which associates an integer to a pair of projections whose difference is compact. They remarked that the essential codimension is zero if and only if the projections are conjugated by a unitary which is a compact perturbation of the identity. Recently, essential codimension has turned up in an unexpected place: the study of diagonals of operators. In this talk we explore the connection between essential codimension and diagonals as well as recent results extending the Brown--Douglas--Fillmore result to C*-algebras. This talk is based on joint work with Victor Kaftal and Ping W. Ng.
Host: John McCarthy