English

Wold-type decomposition for $\mathcal{U}_n$-twisted contractions

Functional Analysis 2023-02-21 v3

Abstract

Let n>1n>1, and {Uij}\{U_{ij}\} for 1i<jn1 \leq i < j \leq n be (n2)\binom{n}{2} commuting unitaries on a Hilbert space H\mathcal{H} such that Uji:=UijU_{ji}:=U^*_{ij}. An nn-tuple of contractions (T1,,Tn)(T_1, \dots, T_n) on H\mathcal{H} is called Un\mathcal{U}_n-twisted contraction with respect to a twist {Uij}i<j\{U_{ij}\}_{i<j} if T1,,TnT_1, \dots, T_n satisfy TiTj=UijTjTi;TiTj=UijTjTi\mboxandTkUij=UijTk T_iT_j=U_{ij}T_jT_i; \hspace{0.5cm} \hspace{1cm} T_i^*T_j= U^*_{ij}T_jT_i^* \hspace{0.5cm} \mbox{and} \hspace{0.5cm} T_kU_{ij} =U_{ij}T_k for all i,j,k=1,,ni,j,k=1, \dots, n and iji \neq j. We obtain a recipe to calculate the orthogonal spaces of the Wold-type decomposition for Un\mathcal{U}_n-twisted contractions on Hilbert spaces. As a by-product, a new proof as well as complete structure for U2\mathcal{U}_2-twisted (or pair of doubly twisted) and Un\mathcal{U}_n-twisted isometries have been established.

Keywords

Cite

@article{arxiv.2207.02115,
  title  = {Wold-type decomposition for $\mathcal{U}_n$-twisted contractions},
  author = {Satyabrata Majee and Amit Maji},
  journal= {arXiv preprint arXiv:2207.02115},
  year   = {2023}
}

Comments

20 pages, title changed and revised. To appear in Journal of Mathematical Analysis and Applications

R2 v1 2026-06-24T12:14:40.135Z