Translation Monoids and Recursive Evaluation in Finite Binary Algebras

TL;DR

This paper explores the structure of translation monoids in finite binary algebras, revealing how recursive evaluation arrays are governed by these monoids and analyzing their algebraic properties.

Contribution

It establishes a connection between recursive evaluation arrays and translation monoids, providing new insights into their algebraic structure and ideal chains.

Findings

Recursive arrays are governed by the translation monoid T(A).

Rank defines a chain of two-sided ideals in T(A).

Minimum-rank elements form a minimal nonempty two-sided ideal.

Abstract

Let \(A=(A,\star)\) be a finite binary algebra, not necessarily associative. For each \(n\geq 1\), every full binary bracketing on \(x_1,\dots,x_n\) determines an \(n\)-ary term operation on \(A\), and hence an evaluation word obtained by listing its values on \(A^n\) in lexicographic order. This produces an \(m^n\times C_{n-1}\) array, where \(m=|A|\) and \(C_{n-1}\) is the \((n-1)\)st Catalan number. We show that the recursive structure of these arrays is governed by the translation monoid \[ T(A)=\langle L_a,R_a:a\in A\rangle\leq A^A, \qquad L_a(x)=a\star x,\quad R_a(x)=x\star a. \] More precisely, context maps arising from subterms are exactly the elements of \(T(A)\), so every element of the translation monoid occurs as a recursive block map. We also prove that rank defines a natural chain of two-sided ideals in \(T(A)\), that the minimum-rank elements form a minimal nonempty two-sided ideal, and that Green's \(\mathcal J\)-classes are contained in rank layers. Finally, we show by example that equal rank does not determine the \(\mathcal J\)-class in general.