The Subalgebra Lattice of A Finite Diagonal–Free Two–Dimensional Cylindric Algebra

Abstract

Diagonal–free two–dimensional cylindric algebras (Df2−algebras for short) are Boolean algebras enriched with two existential quantifiers which commute. Df2−algebras were introduced by A. Tarski, L. Chin and F. Thompson with the purpose of providing an algebraic device for the study of the first–order predicate calculus with two variables. This work is devoted to problems related to finite Df2−algebras. More precisely, we study and describe the family of subalgebras of a given finite Df2−algebra. Then, identifying the algebras of this family which are isomorphic, we provide a full description of the lattice of all non–isomorphic subalgebras of a given finite Df2−algebra.