English

Term inequalities in finite algebras

Logic 2016-01-20 v1

Abstract

Given an algebra A\mathbf{A}, and terms s(x1,x2,xk)s(x_{1},x_{2},\dots x_{k}) and t(x1,x2,xk)t(x_{1},x_{2},\dots x_{k}) of the language of A{\mathbf A}, we say that ss and tt are {\em separated} in A{\mathbf A} iff for all a1,a2akAa_{1},a_{2}\dots a_{k}\in A, s(a1,a2,ak)s(a_{1},a_{2},\dots a_{k}) and t(a1,a2,ak)t(a_{1},a_{2},\dots a_{k}) are never equal. We prove that given two terms that are separated in any algebra, there exists a finite algebra in which they are separated. As a corollary, we obtain that whenever the sentence σ\sigma is a universally quantified conjunction of negated atomic formulas, σ\sigma is consistent iff it has a finite model.

Keywords

Cite

@article{arxiv.1601.04911,
  title  = {Term inequalities in finite algebras},
  author = {David Hobby},
  journal= {arXiv preprint arXiv:1601.04911},
  year   = {2016}
}