Abstract
We investigate the possible values of the numbers of congruences of finite lattices of an arbitrary but fixed cardinality. Motivated by a result of Freese and continuing Czédli’s recent work, we prove that the third, fourth and fifth largest numbers of congruences of an n–element lattice are: 5 ⋅ 2n− 5 if n ≥ 5, 2n− 3 and 7 ⋅ 2n− 6 if n ≥ 6, respectively. We also determine the structures of the n–element lattices having 5 ⋅ 2n− 5, 2n− 3, respectively 7 ⋅ 2n− 6 congruences, along with the structures of their congruence lattices.
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Acknowledgements
This work was supported by the research grant Proprietà d’Ordine Nella Semantica Algebrica delle Logiche Non–classiche of Università degli Studi di Cagliari, Regione Autonoma della Sardegna, L. R. 7/2007, n. 7, 2015, CUP: F72F16002920002, as well as the NFSR of Hungary (OTKA), grant number K 115518.
We thank the anonymous referee for devoting his or her time to carefully reading our paper, for correcting our terminology and providing useful suggestions on how to improve the form of this article, and for undergoing this refereing work with responsibility and professionalism.
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Mureşan, C., Kulin, J. On the Largest Numbers of Congruences of Finite Lattices. Order 37, 445–460 (2020). https://doi.org/10.1007/s11083-019-09514-2
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DOI: https://doi.org/10.1007/s11083-019-09514-2