English

Clonoids between modules

Rings and Algebras 2024-04-17 v3

Abstract

Clonoids are sets of finitary functions from an algebra A\mathbb{A} to an algebra B\mathbb{B} that are closed under composition with term functions of A\mathbb{A} on the domain side and with term functions of B\mathbb{B} on the codomain side. For A,B\mathbb{A},\mathbb{B} (polynomially equivalent to) finite modules we show: If A,B\mathbb{A},\mathbb{B} have coprime order and the congruence lattice of A\mathbb{A} is distributive, then there are only finitely many clonoids from A\mathbb{A} to B\mathbb{B}. This is proved by establishing for every natural number kk a particular linear equation that all kk-ary functions from A\mathbb{A} to B\mathbb{B} satisfy. Else if A,B\mathbb{A},\mathbb{B} do not have coprime order, then there exist infinite ascending chains of clonoids from A\mathbb{A} to B\mathbb{B} ordered by inclusion. Consequently any extension of A\mathbb{A} by B\mathbb{B} has countably infinitely many 22-nilpotent expansions up to term equivalence.

Keywords

Cite

@article{arxiv.2307.00076,
  title  = {Clonoids between modules},
  author = {Peter Mayr and Patrick Wynne},
  journal= {arXiv preprint arXiv:2307.00076},
  year   = {2024}
}
R2 v1 2026-06-28T11:19:21.178Z