Homotopy Types of Small Semigroups

Fuente: arXiv
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Autor principal: Sweeney, Dennis
Formato: Preprint
Publicado: 2025
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author Sweeney, Dennis
author_facet Sweeney, Dennis
contents We algorithmically compute integral Eilenberg-MacLane homology of all semigroups of order at most $8$ and present some particular semigroups with notable classifying spaces, refuting conjectures of Nico. Along the way, we give an alternative topological proof of the fact that if a finite semigroup $S$ has a left-simple or right-simple minimal ideal $K(S)$, then the classifying space $BS$ is homotopy equivalent to the classifying space $B(GS)$ of the group completion. We also describe an algorithm for computing the group completion $GS$ of a finite semigroup $S$ using asymptotically fewer than $|S|^2$ semigroup operations. Finally, we show that the set of homotopy types of classifying spaces of finite monoids is closed under suspension.
format Preprint
id arxiv_https___arxiv_org_abs_2502_05276
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Homotopy Types of Small Semigroups
Sweeney, Dennis
Algebraic Topology
20M50 (Primary) 55U10, 55-08, 55-11 (Secondary)
We algorithmically compute integral Eilenberg-MacLane homology of all semigroups of order at most $8$ and present some particular semigroups with notable classifying spaces, refuting conjectures of Nico. Along the way, we give an alternative topological proof of the fact that if a finite semigroup $S$ has a left-simple or right-simple minimal ideal $K(S)$, then the classifying space $BS$ is homotopy equivalent to the classifying space $B(GS)$ of the group completion. We also describe an algorithm for computing the group completion $GS$ of a finite semigroup $S$ using asymptotically fewer than $|S|^2$ semigroup operations. Finally, we show that the set of homotopy types of classifying spaces of finite monoids is closed under suspension.
title Homotopy Types of Small Semigroups
topic Algebraic Topology
20M50 (Primary) 55U10, 55-08, 55-11 (Secondary)
url https://arxiv.org/abs/2502.05276