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Partition algebras as monoid algebras

Combinatorics 2025-07-22 v1

Abstract

Wilcox has considered a twisted semigroup algebra structure on the partition algebra CAk(n)\mathbb{C}A_k(n), but it appears that there has not previously been any known basis that gives CAk(n)\mathbb{C}A_k(n) the structure of a "non-twisted" semigroup algebra or a monoid algebra. This motivates the following problem, for the non-degenerate case whereby nC{0,1,,2k2}n \in \mathbb{C} \setminus \{ 0, 1, \ldots, 2 k - 2 \} so that CAk(n) \mathbb{C}A_k(n) is semisimple. How could a basis Mk=MM_{k} = M of CAk(n) \mathbb{C}A_k(n) be constructed so that MM is closed under the multiplicative operation on CAk(n)\mathbb{C}A_k(n), in such a way so that MM is a monoid under this operation, and how could a product rule for elements in MM be defined in an explicit and combinatorial way in terms of partition diagrams? We construct a basis MM of the desired form using Halverson and Ram's matrix unit construction for partition algebras, Benkart and Halverson's bijection between vacillating tableaux and set-partition tableaux, an analogue given by Colmenarejo et al. for partition diagrams of the RSK correspondence, and a variant of a result due to Hewitt and Zuckerman characterizing finite-dimensional semisimple algebras that are isomorphic to semigroup algebras.

Keywords

Cite

@article{arxiv.2507.14313,
  title  = {Partition algebras as monoid algebras},
  author = {John M. Campbell},
  journal= {arXiv preprint arXiv:2507.14313},
  year   = {2025}
}

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