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modified_symmetric_group

Modified symmetric group

A modified symmetric group is any member of a certain sequence $(S_N')_{N\in \N}$ of classical orthogonal matrix groups.

Definition

As a matrix group

For every $N\in \N$ the modified symmetric group for dimension $N$ is the subgroup of the general linear group $\mathrm{GL}(N,\C)$ given by all permutation $N\times N$-matrices multiplied by a factor of $1$ or $-1$, i.e., the set

$$S_N\colon\hspace{-0.6em}=\{ u\in \C^{N\times N}\,\vert\, \exists r\in \{-1,1\},\,\forall_{i,j=1}^N: u_{i,j}\in\{0,1\},\,{\textstyle\sum_{\ell=1}^N} u_{i,\ell}={\textstyle\sum_{k=1}^N} u_{k,j}=r\},$$

where $u=(u_{i,j})_{i,j=1}^N$.

As a direct product

The modified symmetric group for dimension $N$, where $N\in \N$, can also be defined as the direct product of groups $S_N'\colon\hspace{-0.66em}=\Z_2\times S_N$ of the cyclic group $\Z_2\equiv \Z/2\Z$ of order $2$ and the symmetric group for dimension $N$.

Basic properties

The modified symmetric groups $(S_N')_{N\in \N}$ are an easy family of compact matrix quantum groups, i.e., the intertwiner spaces of their corepresentation categories are induced by a category of partitions. More precisely, it is the category of partitions of even size that induces the corepresentation categories of $(S_N')_{N\in \N}$. Its canonical generating set of partitions is $\{\crosspart,\fourpart,\singleton\otimes\singleton\}$.

Representation theory

Cohomology

References

modified_symmetric_group.txt · Last modified: 2021/11/23 11:56 (external edit)