Mean weak length

Fuente: arXiv
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Autores principales: Bai, Zihan, Liang, Bingbing
Formato: Preprint
Publicado: 2026
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author Bai, Zihan
Liang, Bingbing
author_facet Bai, Zihan
Liang, Bingbing
contents We introduce a weak version of the classical length function, termed the weak length function, defined on subsets of $R$-modules over a unital ring $R$, and further consider the concept of mean weak length for $RΓ$-modules associated with an amenable group $Γ$. Under an appropriate upgrading condition together with certain mild assumptions, we establish that the mean weak length function is additive with respect to short exact sequences. This result has two consequences. First, we provide a purely algebraic proof of the additivity of algebraic entropy, which is a property originally established via topological entropy methods. Second, within our unified framework, we give an alternative and conceptual proof of the additivity of mean length, previously obtained by Li-Liang and Virilli using different approaches.
format Preprint
id arxiv_https___arxiv_org_abs_2605_06715
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Mean weak length
Bai, Zihan
Liang, Bingbing
Rings and Algebras
Dynamical Systems
Group Theory
2020 37A35
We introduce a weak version of the classical length function, termed the weak length function, defined on subsets of $R$-modules over a unital ring $R$, and further consider the concept of mean weak length for $RΓ$-modules associated with an amenable group $Γ$. Under an appropriate upgrading condition together with certain mild assumptions, we establish that the mean weak length function is additive with respect to short exact sequences. This result has two consequences. First, we provide a purely algebraic proof of the additivity of algebraic entropy, which is a property originally established via topological entropy methods. Second, within our unified framework, we give an alternative and conceptual proof of the additivity of mean length, previously obtained by Li-Liang and Virilli using different approaches.
title Mean weak length
topic Rings and Algebras
Dynamical Systems
Group Theory
2020 37A35
url https://arxiv.org/abs/2605.06715