Fredholm operators on $C^{\ast }$-algebras

Abstract

The aim of this note is to generalize the notion of Fredholm operator to an arbitrary $C^{\ast }$-algebra. Namely, we define "finite type" elements in an axiomatic way, and also we define Fredholm type element $a$ as such element of a given $C^{\ast }$-algebra for which there are finite type elements $p$ and $q$ such that $(1-q)a(1-p)$ is "invertible". We derive index theorem for such operators. In applications we show that classical Fredholm operators on a Hilbert space, Fredholm operators in the sense of Breuer, Atiyah and Singer on a properly infinite von Neumann algebra, and Fredholm operators on Hilbert $C^{\ast }$-modules over an unital $C^{\ast }$-algebra in the sense of Mishchenko and Fomenko are special cases of our theory.

Cited by in corpus (2)

• Semi-Fredholm theory in C*-algebras
• On New Approach to semi-Fredholm theory in unital C*-algebras