# Journal of Operator Theory

Volume 52, Issue 1, Summer 2004 pp. 61-87.

Partial-isometric crossed products by semigroups of endomorphisms**Authors**: Janny Lindiarni (1) and Iain Raeburn (2)

**Author institution:**(1) School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, NS@ 2308, Australia

(2) School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, NS@ 2308, Australia

**Summary:**Let $\Gamma^+$ be the positive cone in a totally ordered abelian group $\Gamma$, and let $\alpha$ be an action of $\Gamma^+$ by endomorphisms of a $C^*$-algebra $A$. We consider a new kind of crossed-product $C^*$-algebra $A\times_\alpha\Gamma^+$, which is generated by a faithful copy of $A$ and a representation of $\Gamma^+$ as partial isometries. We claim that these crossed products provide a rich and tractable family of Toeplitz algebras for product systems of Hilbert bimodules, as recently studied by Fowler, and we illustrate this by proving detailed structure theorems for actions by forward and backward shifts.

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