Strongly sofic monoids, sofic topological entropy, and surjunctivity

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Main Authors: Ceccherini-Silberstein, Tullio, Coornaert, Michel, Phung, Xuan Kien
Format: Preprint
Published: 2024
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author Ceccherini-Silberstein, Tullio
Coornaert, Michel
Phung, Xuan Kien
author_facet Ceccherini-Silberstein, Tullio
Coornaert, Michel
Phung, Xuan Kien
contents We introduce the class of strongly sofic monoids. This class of monoids strictly contains the class of sofic groups and is a proper subclass of the class of sofic monoids. We define and investigate sofic topological entropy for actions of strongly sofic monoids on compact spaces. We show that sofic topological entropy is a topological conjugacy invariant for such actions and use this fact to prove that every strongly sofic monoid is surjunctive. This means that if $M$ is a strongly sofic monoid and $A$ is a finite alphabet set, then every injective cellular automaton $τ\colon A^M \to A^M$ is surjective. As an application, we prove that the monoid algebra of a strongly sofic monoid with coefficients in an arbitrary field is always stably finite. Our results are extensions to strongly sofic monoids of two previously known properties of sofic groups. The first one is the celebrated Gromov-Weiss theorem asserting that every sofic group is surjunctive. The second is the Elek-Szabó theorem which says that group algebras of sofic groups satisfy Kaplansky's stable finiteness conjecture.
format Preprint
id arxiv_https___arxiv_org_abs_2410_17688
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Strongly sofic monoids, sofic topological entropy, and surjunctivity
Ceccherini-Silberstein, Tullio
Coornaert, Michel
Phung, Xuan Kien
Group Theory
Dynamical Systems
Rings and Algebras
We introduce the class of strongly sofic monoids. This class of monoids strictly contains the class of sofic groups and is a proper subclass of the class of sofic monoids. We define and investigate sofic topological entropy for actions of strongly sofic monoids on compact spaces. We show that sofic topological entropy is a topological conjugacy invariant for such actions and use this fact to prove that every strongly sofic monoid is surjunctive. This means that if $M$ is a strongly sofic monoid and $A$ is a finite alphabet set, then every injective cellular automaton $τ\colon A^M \to A^M$ is surjective. As an application, we prove that the monoid algebra of a strongly sofic monoid with coefficients in an arbitrary field is always stably finite. Our results are extensions to strongly sofic monoids of two previously known properties of sofic groups. The first one is the celebrated Gromov-Weiss theorem asserting that every sofic group is surjunctive. The second is the Elek-Szabó theorem which says that group algebras of sofic groups satisfy Kaplansky's stable finiteness conjecture.
title Strongly sofic monoids, sofic topological entropy, and surjunctivity
topic Group Theory
Dynamical Systems
Rings and Algebras
url https://arxiv.org/abs/2410.17688