On Nontrivial Weak Dicomplementations and the Lattice Congruences that Preserve Them

Abstract

AbstractWe study the existence of nontrivial and of representable (dual) weak complementations, along with the lattice congruences that preserve them, in different constructions of bounded lattices, then use this study to determine the finite (dual) weakly complemented lattices with the largest numbers of congruences, along with the structures of their congruence lattices. It turns out that, if $$n\ge 7$$ n ≥ 7 is a natural number, then the four largest numbers of congruences of the n–element (dual) weakly complemented lattices are: $$2^{n-2}+1$$ 2 n - 2 + 1 , $$2^{n-3}+1$$ 2 n - 3 + 1 , $$5\cdot 2^{n-6}+1$$ 5 · 2 n - 6 + 1 and $$2^{n-4}+1$$ 2 n - 4 + 1 , which yields the fact that, for any $$n\ge 5$$ n ≥ 5 , the largest and second largest numbers of congruences of the n–element weakly dicomplemented lattices are $$2^{n-3}+1$$ 2 n - 3 + 1 and $$2^{n-4}+1$$ 2 n - 4 + 1 . For smaller numbers of elements, several intermediate numbers of congruences appear between the elements of these sequences.