Fast Fourier Transforms for the Rook Monoid

We define the notion of the Fourier transform for the rook monoid (also called the symmetric inverse semigroup) and provide two efficient divide-and-conquer algorithms (fast Fourier transforms, or FFTs) for computing it. This paper marks the first extension of group FFTs to non-group semigroups

Jucys-Murphy elements and Grothendieck groups for generalized rook monoids

We consider a tower of generalized rook monoid algebras over the field $\mathbb{C}$ of complex numbers and observe that the Bratteli diagram associated to this tower is a simple graph. We construct simple modules and describe Jucys-Murphy elements for generalized rook monoid algebras. Over an algebraically closed field $\Bbbk$ of positive characteristic $p$, utilizing Jucys-Murphy elements of rook monoid algebras, for $0\leq i\leq p-1$ we define the corresponding $i$-restriction and $i$-induction functors along with two extra functors. On the direct sum $\mathcal{G}_{\mathbb{C}}$ of the Grothendieck groups of module categories over rook monoid algebras over $\Bbbk$, these functors induce an action of the tensor product of the universal enveloping algebra $U(\hat{\mathfrak{sl}}_p(\mathbb{C}))$ and the monoid algebra $\mathbb{C}[\mathcal{B}]$ of the bicyclic monoid $\mathcal{B}$. Furthermore, we prove that $\mathcal{G}_{\mathbb{C}}$ is isomorphic to the tensor product of the basic representation of $U(\hat{\mathfrak{sl}}_{p}(\mathbb{C}))$ and the unique infinite-dimensional simple module over $\mathbb{C}[\mathcal{B}]$, and also exhibit that $\mathcal{G}_{\mathbb{C}}$ is a bialgebra. Under some natural restrictions on the characteristic of $\Bbbk$, we outline the corresponding result for generalized rook monoids.Comment: Minor changes and added a few more references. Comments welcome

Generalized rook-Brauer algebras and their homology

Rook-Brauer algebras are a family of diagram algebras. They contain many interesting subalgebras: rook algebras, Brauer algebras, Motzkin algebras, Temperley-Lieb algebras and symmetric group algebras. In this paper, we generalize the rook-Brauer algebras and their subalgebras by allowing more structured diagrams. We introduce equivariance by labelling edges of a diagram with elements of a group $G$. We introduce braiding by insisting that when two strands cross, they do so as either an under-crossing or an over-crossing. We also introduce equivariant, braided diagrams by combining these structures. We then study the homology of our diagram algebras, as pioneered by Boyd and Hepworth, using methods introduced by Boyde. We show that, given certain invertible parameters, we can identify the homology of our generalized diagram algebras with the group homology of the braid groups $B_n$ and the semi-direct products $G^n\rtimes \Sigma_n$ and $G^n\rtimes B_n$. This allows us to deduce homological stability results for our generalized diagram algebras. We also prove that for diagrams with an odd number of edges, the homology of equivariant Brauer algebras and equivariant Temperley-Lieb algebras can be identified with the group homology of $G^n\rtimes \Sigma_n$ and $G^n$ respectively, without any conditions on parameters.Comment: 28 pages. Comments welcom