English

On doubly commuting operators in $C_{1, r}$ class and quantum annulus

Functional Analysis 2026-03-05 v2

Abstract

For 0<r<1 0 < r < 1 , let Ar={zC:r<z<1} \mathbb{A}_r = \{ z \in \mathbb{C} : r < |z| < 1 \} be the annulus with boundary Ar=TrT \partial \overline{\mathbb{A}}_r = \mathbb{T} \cup r\mathbb{T} , where T \mathbb{T} is the unit circle in the complex plane C\mathbb C. We study the class of operators C1,r={T:T is invertible and T,rT11}, C_{1,r} = \{ T : T \text{ is invertible and } \|T\|, \|rT^{-1}\| \leq 1 \}, introduced by Bello and Yakubovich. Any operator TT for which the closed annulus Ar\overline{\mathbb{A}}_r is a spectral set is in C1,rC_{1,r}. The class C1,rC_{1, r} is closely related to the \textit{quantum annulus} which is given by QAr={T:T is invertible and rT,rT11}. QA_r = \{ T : T \text{ is invertible and } \|rT\|, \|rT^{-1}\| \leq 1 \}. McCullough and Pascoe proved that an operator in QAr QA_r admits a dilation to an operator S S satisfying (r2+r2)ISSS1S=0(r^{-2} + r^2)I - S^*S - S^{-1}S^{-*} = 0. An analogous dilation result holds for operators in C1,r C_{1,r} class. We extend these dilation results to doubly commuting tuples of operators in quantum annulus as well as in C1,rC_{1,r} class. We also provide characterizations and decomposition results for such tuples.

Keywords

Cite

@article{arxiv.2503.23754,
  title  = {On doubly commuting operators in $C_{1, r}$ class and quantum annulus},
  author = {Nitin Tomar},
  journal= {arXiv preprint arXiv:2503.23754},
  year   = {2026}
}

Comments

Journal of Operator Theory, To appear

R2 v1 2026-06-28T22:40:03.512Z