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Shifts on Type II1 Factors

Published online by Cambridge University Press:  20 November 2018

Geoffrey L. Price*
Affiliation:
United States Naval Academy, Annapolis, Maryland
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A shift on a unital C*-algebras is a *-endomorphism α of which fixes the identity and has the property that the intersection of the ranges of αn for n = 1, 2, 3, … consists only of multiples of the identity. In [4] R. T. Powers introduced the notion of a shift on a C*-algebra and considered both discrete and continuous one-parameter semi-groups of shifts. In this paper we focus on discrete shifts. We use a construction of Powers to obtain shifts on certain unital AF C*-algebras. These are defined by constructing a set {ui:i = 1, 2, …} of self-adjoint unitary operators which pairwise either commute or anticommute. Setting α(ui) = ui + 1, determines an endomorphism on the group algebra generated by the ui's. This algebra is called a binary shift algebra. By passing to the (unique) C*-algebra completion we obtain an AF-algebra on which a defines a shift.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1987

References

1. Bratteli, O., Inductive limits of finite-dimensional C*-algebras, Trans. Amer. Math. Soc. 171 (1972), 195234.Google Scholar
2. Goldman, M., On subfactors of factors of type II1 , Mich. Math. Jour. 6 (1959), 167172.Google Scholar
3. Jones, V. F. R., Index for subfactors, Invent. Math. 72 (1983), 125.Google Scholar
4. Powers, R. T., An index theory for semigroups of *-endomorphisms of B(H) and type II1 factors, Can. J. Math., to appearCrossRefGoogle Scholar