arXiv subjects

Alexander Betz

Publications and source records attributed to Alexander Betz.

5 recordsLinked to original sources

arXiv2025

Weak Hopf algebra actions as fusion category actions

This article develops the theory of fusion categories acting on algebras. We will demonstrate that weak Hopf algebra actions on algebras correspond to specific actions of fusion categories. As an application of this theory, we introduce a family of filtered actions of weak Hopf algebras on the path algebra, and for weak Hopf algebras whose representation categories are equivalent to $\text{PSU(2)}_{p-2}$, we describe all of the separable based fusion category actions in terms of weak Hopf algebra actions.

math.QA↗

arXiv2025

Actions of Fusion Categories on Path Algebras

In this article, we introduce the notion of a based action of a fusion category on an algebra. We will build some general theory to motivate our interest in based actions, and then apply this theory to understand based actions of fusion categories on path algebras. Our results demonstrate that a separable idempotent split based action of a fusion category $C$ on a path algebra can be characterized in terms of $C$ module categories and their associated module endofunctors. As a specific application, we fully classify separable idempotent split based actions of the family of fusion categories $\text{PSU}(2)_{p-2}$ on path algebras up to conjugacy.

math.QA↗

arXiv2021

Finite Permutation Groups with Few Orbits Under the Action on the Power Set

We study the orbits under the natural action of a permutation group $G \subseteq S_n$ on the powerset $\mathscr{P}(\{1, \dots , n\})$. The permutation groups having exactly $n+1$ orbits on the powerset can be characterized as set-transitive groups and were fully classified in \cite{BP55}. In this paper, we establish a general method that allows one to classify the permutation groups with $n+r$ set-orbits for a given $r$, and apply it to integers $2 \leq r \leq 15$ using the computer algebra system GAP.

math.GR↗

arXiv2020

Classifying groups with a small number of subgroups

We provide lower bounds on the number of subgroups of a group $G$ as a function of the primes and exponents appearing in the prime factorization of $|G|$. Using these bounds, we classify all abelian groups with 22 or fewer subgroups, and all non-abelian groups with 19 or fewer subgroups. This allows us to extend the integer sequence A274847 \cite{OEIS} introduced by Slattery in \cite{Slattery}.

math.GR↗

arXiv2020

On the odd order composition factors of finite linear groups

In this paper, we study the product of orders of composition factors of odd order in a composition series of a finite linear group. First we generalize a result by Manz and Wolf about the order of solvable linear groups of odd order. Then we use this result to find bounds for the product of orders of composition factors of odd order in a composition series of a finite linear group.

math.GR↗