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# Journal of Operator Theory

Volume 65, Issue 1, Winter 2011  pp. 145-155.

Convex polytopes and the index of Wiener-Hopf operators

Authors Alexander Alldridge
Author institution: Institut fuer Mathematik, Universitaet Paderborn, 33098 Paderborn, Germany and Mathematisches Institut, Universitaet zu Koeln, Weyertal 86--90, 50939 Koeln, Germany

Summary:  We study the $C^*$-algebra of Wiener--Hopf operators $A_\Omega$ on a cone $\Omega$ with polyhedral base $P$. As is known, a sequence of symbol maps may be defined, and their kernels give a filtration by ideals of $A_\Omega$, with liminary subquotients. One may define $K$-group valued `index maps'' between the subquotients. These form the $E^1$ term of the Atiyah--Hirzebruch type spectral sequence induced by the filtration. We show that this $E^1$ term may, as a complex, be identified with the cellular complex of $P$, considered as CW-complex by taking convex faces as cells. It follows that $A_\Omega$ is $KK$-contractible, and that $A_\Omega/\knums$ and $S$ are $KK$-equivalent. Moreover, the isomorphism class of $A_\Omega$ is a complete invariant for the combinatorial type of $P$.

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