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Von Neumann's inequality for commuting weighted shifts
We show that every multivariable contractive weighted shift dilates to a
tuple of commuting unitaries, and hence satisfies von Neumann's inequality.
This answers a question of Lubin and Shields. We also exhibit a closely related
-tuple of commuting contractions, similar to Parrott's example, which does
not dilate to a -tuple of commuting unitaries.Comment: 13 pages; minor change
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