English

Operators on Hilbert Space having $\Gamma_{E(3; 3; 1, 1, 1)}$ and $\Gamma_{E(3; 2; 1, 2)}$ as Spectral Sets

Functional Analysis 2025-10-30 v1

Abstract

A 77-tuple of commuting bounded operators T=(T1,,T7)\textbf{T} = (T_1, \dots, T_7) on a Hilbert space H\mathcal{H} is called a \textit{ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)} -contraction} if ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)} is a spectral set for T.\textbf{T}. Let (S1,S2,S3)(S_1, S_2, S_3) and (S~1,S~2)(\tilde{S}_1, \tilde{S}_2) be tuples of commuting bounded operators defined on a Hilbert space H\mathcal{H} with SiS~j=S~jSiS_i\tilde{S}_j = \tilde{S}_jS_i for 1i31 \leqslant i \leqslant 3 and 1j21 \leqslant j \leqslant 2. We say that S=(S1,S2,S3,S~1,S~2)\textbf{S} = (S_1, S_2, S_3, \tilde{S}_1, \tilde{S}_2) is a ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)} -contraction if ΓE(3;2;1,2) \Gamma_{E(3; 2; 1, 2)} is a spectral set for S\textbf{S}. We derive various properties of ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-contractions and ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-contractions and establish a relationship between them. We discuss the fundamental equations for ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1,1 )}-contractions and ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-contractions. We explore the structure of ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-unitaries and ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-unitaries and elaborate on the relationship between them. We also study various properties of ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-isometries and ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-isometries. We discuss the Wold Decomposition for a ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-isometry and a ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-isometry. We further outline the structure theorem for a pure ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-isometry and a pure ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-isometry.

Keywords

Cite

@article{arxiv.2510.25666,
  title  = {Operators on Hilbert Space having $\Gamma_{E(3; 3; 1, 1, 1)}$ and $\Gamma_{E(3; 2; 1, 2)}$ as Spectral Sets},
  author = {Dinesh Kumar Keshari and Avijit Pal and Bhaskar Paul},
  journal= {arXiv preprint arXiv:2510.25666},
  year   = {2025}
}