Von Neumann’s Inequality for Commuting Weighted Shifts
نویسنده
چکیده
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 3-tuple of commuting contractions, similar to Parrott’s example, which does not dilate to a 3-tuple of commuting unitaries.
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