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category_of_non-crossing_partitions_of_even_size

Category of non-crossing partitions of even size

The category of non-crossing partitions of even size is a Banica-Speicher category of partitions inducing the corepresentation category of the free modified symmetric quantum groups.

Definition

By the category of non-crossing partitions of even size one denotes the subcategory of the category of all partitions $\Pscr$ whose morphism class is the set of all non-crossing partitions of even size. It was introduced by Banica and Speicher in [BanSp09].

  • For all $k,l\in \{0\}\cup \N$, a partition $p\in \Pscr(k,l)$ is said to be of even size if $k+l$ is an even number, i.e., if $p$ has evenly many points.
  • It is said to be non-crossing if there exist no blocks $B$ and $B'$ of $p$ with $B\neq B'$ and no legs $i,j\in B$ and $i',j'\in B'$ such that $i\prec i'\prec j$ and $i'\prec j\prec j'$ with respect to the cyclic order of $p$. See also category of all non-crossing partitions.
  • The name set of all non-crossing partitions of even size is to be taken literally.

It is sometimes said that the category of non-crossing partitions of even size is the even part of the category $\mathrm{NC}$ of all non-crossing partitions.

Canonical generator

The category of all non-crossing partitions of even size is the subcategory of $\Pscr$ generated by the set of partitions $\{\fourpart,\singleton \otimes\singleton\}$.

Associated easy quantum group

Via Tannaka-Krein duality for compact quantum groups, the category of all non-crossing partitions of even size corresponds to the family $(S^{\prime +}_N)_{N\in \N}$ of free modified symmetric quantum groups.

References


[BanSp09] Banica, Teodor and Speicher, Roland, 2009. Liberation of orthogonal Lie groups. Advances in Mathematics, 222, pp.1461–150.
category_of_non-crossing_partitions_of_even_size.txt · Last modified: 2021/11/23 11:56 (external edit)