English

Admissible Fundamental Operators and Models for $\Gamma_{E(3; 3; 1, 1, 1)}$-contraction and $\Gamma_{E(3; 2; 1, 2)}$-contraction

Functional Analysis 2025-11-05 v1

Abstract

We show that for a given pure contraction T7T_7 acting on a Hilbert space H\mathcal{H}, if (F~1,,F~6)B(DT7)(\tilde{F}_1, \dots, \tilde{F}_6) \in \mathcal{B}(\mathcal{D}_{T^*_7}) with [F~i,F~j]=0,[F~i,F~7j]=[F~j,F~7i][\tilde{F}_i, \tilde{F}_j] = 0, [\tilde{F}^*_i, \tilde{F}_{7-j}] = [\tilde{F}^*_j, \tilde{F}_{7-i}],w(F~i+F~7iz)1w(\tilde{F}^*_i + \tilde{F}_{7-i}z) \leqslant 1 and these operators satisfy (F~i+F~7iz)ΘT7(z)=ΘT7(z)(Fi+F7iz)for allzD(\tilde{F}^*_i + \tilde{F}_{7-i}z)\Theta_{T_7}(z) = \Theta_{T_7}(z)(F_i + F^*_{7-i}z) \,\, \text{for all} \,\, z \in \mathbb{D} for 1i,j61 \leqslant i, j \leqslant 6 for some (F1,,F6)B(DT7)(F_1, \dots, F_6) \in \mathcal{B}(\mathcal{D}_{T_7}) with w(Fi+F7iz)1w(F^*_i + F_{7-i}z) \leqslant 1 for 1i61 \leqslant i \leqslant 6, then there exists a ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-contraction (T1,,T7)(T_1, \dots, T_7) such that F1,,F6F_1, \dots, F_6 are the fundamental operators of (T1,,T7)(T_1, \dots, T_7) and F~1,,F~6\tilde{F}_1, \dots, \tilde{F}_6 are the fundamental operators of (T1,,T7)(T^*_1, \dots, T^*_7). We also prove similar type of result for pure ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-contraction. We explicitly construct a ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-unitary (respectively, a ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-unitary) starting from a ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-contraction (respectively, a ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-contraction). Further, we develop functional models for general ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-isometries (respectively, ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-isometries). In particular, we construct Douglas-type and Sz.-Nazy-Foias-type models for ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-contractions (respectively, ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-contractions). Finally, we present a Schaffer-type model for the ΓE(3;3;1,1,1)\Gamma_{E(3; 3; 1, 1, 1)}-isometric dilation (respectively, the ΓE(3;2;1,2)\Gamma_{E(3; 2; 1, 2)}-isometric dilation).

Keywords

Cite

@article{arxiv.2511.02635,
  title  = {Admissible Fundamental Operators and Models for $\Gamma_{E(3; 3; 1, 1, 1)}$-contraction and $\Gamma_{E(3; 2; 1, 2)}$-contraction},
  author = {Avijit Pal and Bhaskar Paul},
  journal= {arXiv preprint arXiv:2511.02635},
  year   = {2025}
}

Comments

This is the initial version of the paper. Final version will submit soon