Abstract
Let H2(ⅅ2) be the Hardy space over the bidisk ⅅ2, and let Mψ,ϕ = [(ψ(z) − ϕ(w))2] be the submodule generated by (ψ(z) − ϕ(w))2, where ψ(z) and ϕ(w) are nonconstant inner functions. The related quotient module is denoted by Nψ,ϕ = H2(ⅅ2) ⊖ Mψ,ϕ. In this paper, we give a complete characterization for the essential normality of Nψ,ϕ. In particular, if ψ(z)= z, we simply write Mψ,ϕ and Nψ,ϕ as Mϕ and Nϕ respectively. This paper also studies compactness of evaluation operators L(0)∣nϕ and R(0)ϕnϕ, essential spectrum of compression operator Sz on Nϕ, essential normality of compression operators Sz and Sw on Nϕ.
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Acknowledgements
The authors are very grateful to professor Rongwei Yang for suggesting this line of research, and for his ongoing encouragement and support.
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Supported by NNSF of China (Grant No. 11971087)
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Wu, C.H., Yu, T. Nψ,ϕ-type Quotient Modules over the Bidisk. Acta. Math. Sin.-English Ser. 36, 943–960 (2020). https://doi.org/10.1007/s10114-020-9347-8
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DOI: https://doi.org/10.1007/s10114-020-9347-8