## Noncommutative Riemann integration and singular traces for C ∗ - algebras

Citations: | 4 - 4 self |

### BibTeX

@TECHREPORT{Guido_noncommutativeriemann,

author = {Daniele Guido and Tommaso Isola},

title = {Noncommutative Riemann integration and singular traces for C ∗ - algebras},

institution = {},

year = {}

}

### Years of Citing Articles

### OpenURL

### Abstract

Given a C ∗-algebra A with a semicontinuous semifinite trace τ acting on the Hilbert space H, we define the family A R of bounded Riemann measurable elements w.r.t. τ as a suitable closure, à la Dedekind, of A, in analogy with one of the classical characterizations of Riemann measurable functions [16], and show that A R is a C ∗-algebra, and τ extends to a semicontinuous semifinite trace on A R. Then, unbounded Riemann measurable operators are defined as the closed operators on H which are affiliated to A ′′ and can be approximated in measure by operators in A R, in analogy with improper Riemann integration. Unbounded Riemann measurable operators form a τ-a.e. bimodule on A R, denoted by AR, and such bimodule contains the functional calculi of selfadjoint elements of A R under unbounded Riemann measurable functions. Besides, τ extends to a bimodule trace on AR. As type II1 singular traces for a semifinite von Neumann algebra M with a normal semifinite faithful (non-atomic) trace τ have been defined as traces on M − M-bimodules of unbounded τ-measurable operators [5], type II1 singular traces for a C ∗-algebra A with a semicontinuous semifinite (non-atomic) trace τ are defined here as traces on A − A-bimodules of unbounded Riemann measurable operators (in AR) for any faithful representation of A. An application of singular traces for C ∗-algebras is contained in [6].