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Operators Cauchy Dual to 2-Hyperexpansive Operators: The Multivariable Case
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Operators Cauchy Dual to 2-Hyperexpansive Operators: The Multivariable Case

Sameer Chavan and Raúl Curto
Integral Equations and Operator Theory, Vol.73(4), pp.481-516
08/2012
DOI: 10.1007/s00020-012-1986-4

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Abstract

As a natural outgrowth of the work done in Chavan (Proc Edin Math Soc 50:637–652, 2007; Studia Math 203:129–162, 2011), we introduce an abstract framework to study generating m-tuples, and use it to analyze hypercontractivity and hyperexpansivity in several variables. These two notions encompass (joint) hyponormality and subnormality, as well as toral and spherical isometric-ness; for instance, the Drury–Arveson 2-shift is a spherical complete hyperexpansion. Our approach produces a unified theory that simultaneously covers toral and spherical hypercontractions (and hyperexpansions). As a byproduct, we arrive at a dilation theory for completely hypercontractive and completely hyperexpansive generating tuples. We can then analyze in detail the Cauchy duals of toral and spherical 2-hyperexpansive tuples. We also discuss various applications to the theory of hypercontractive and hyperexpansive tuples.
hypercontractive Cauchy dual multiplicative dilation hyperexpansive Subnormal generating tuple Mathematics 47A20 47B20 Secondary 47A65 47B47 47B37 Analysis Primary 47A13

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