2006
DOI: 10.1016/j.crma.2006.09.024
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Spectral pictures of 2-variable weighted shifts

Abstract: We study the spectral pictures of (jointly) hyponormal 2-variable weighted shifts with commuting subnormal components. By contrast with all known results in the theory of subnormal single and 2-variable weighted shifts, we show that the Taylor essential spectrum can be disconnected. We do this by obtaining a simple sufficient condition that guarantees disconnectedness, based on the norms of the horizontal slices of the shift. We also show that for every k ≥ 1 there exists a k-hyponormal 2-variable weighted shi… Show more

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Cited by 9 publications
(4 citation statements)
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“…We conclude this section with a recipe to construct non-compact multishifts S λ on T having Taylor spectra with empty interior. One such family of classical multishifts has been exhibited in [49,Example 2]. We now capitalize on it to construct examples of multishifts S λ on T 2,0 × T 2,0 with Taylor spectra of empty interior.…”
Section: A Matrix Decomposition and Essential Spectrummentioning
confidence: 99%
“…We conclude this section with a recipe to construct non-compact multishifts S λ on T having Taylor spectra with empty interior. One such family of classical multishifts has been exhibited in [49,Example 2]. We now capitalize on it to construct examples of multishifts S λ on T 2,0 × T 2,0 with Taylor spectra of empty interior.…”
Section: A Matrix Decomposition and Essential Spectrummentioning
confidence: 99%
“…If in addition, T is a multi-shift, then this always happens as seen above. In view of this, it is interesting to note that there exists a jointly hyponormal 2-shift with disconnected essential spectrum [17,Theorem 2.5].…”
Section: Spectral Theory For Multi-shiftsmentioning
confidence: 99%
“…The class in Theorem 2. 8 contains the examples in [10,Section 5], [11,Corollary 4.7 and Proposition 4.10], [12,Remark 3.5], [13,Theorem 3.10] and [20,Example 2.12]. Finally, in Section 3, we give a complete characterization of hyponormality and subnormality in the class FC of flat, contractive 2-variable weighted shifts T ∈ H 0 with the condition W β = b, where b > 0 is given (see Fig.…”
Section: Introductionmentioning
confidence: 99%