(1 + 1 + 2)-generated lattices of quasiorders

A lattice is (1 + 1 + 2)-generated if it has a four-element generating set such that exactly two of the four generators are comparable. We prove that the lattice Quo(n) of all quasiorders (also known as preorders) of an n-element set is (1 + 1 + 2)-generated for n = 3 (trivially), n = 6 (when Quo(6)...

Teljes leírás

Elmentve itt :
Bibliográfiai részletek
Szerzők: Ahmed Delbrin
Czédli Gábor
Dokumentumtípus: Cikk
Megjelent: 2021
Sorozat:Acta scientiarum mathematicarum 87 No. 3-4
Kulcsszavak:Matematika, Algebra
Tárgyszavak:
doi:10.14232/actasm-021-303-1

Online Access:http://acta.bibl.u-szeged.hu/75848
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490 0 |a Acta scientiarum mathematicarum  |v 87 No. 3-4 
520 3 |a A lattice is (1 + 1 + 2)-generated if it has a four-element generating set such that exactly two of the four generators are comparable. We prove that the lattice Quo(n) of all quasiorders (also known as preorders) of an n-element set is (1 + 1 + 2)-generated for n = 3 (trivially), n = 6 (when Quo(6) consists of 209 527 elements), n = 11, and for every natural number n ≥ 13. In 2017, the second author and J. Kulin proved that Quo(n) is (1 + 1 + 2)-generated if either n is odd and at least 13 or n is even and at least 56. Compared to the 2017 result, this paper presents twenty-four new numbers n such that Quo(n) is (1 + 1 + 2)-generated. Except for Quo(6), an extension of Zádori’s method is used. 
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695 |a Matematika, Algebra 
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