Abstract
Slim semimodular lattices were introduced by G. Grätzer and E. Knapp in 2007, and they have intensively been studied since then. These lattices can be given by \(\mathcal{C}_1\)-diagrams, defined by the author in 2017. We prove that if x and y are incomparable elements in such a lattice L, then their meet has the property that the interval \([x \wedge y, x]\) is a chain, this chain is of a normal slope in every \(\mathcal{C}_1\)-diagram of L, and except possibly for x, the elements of this chain are meet-reducible.
In the direct square K1 of the three-element chain, let X1 and A1 be the set of atoms and the sublattice generated by 0 and the coatoms, respectively. Denote by K2 the unique eight-element lattice embeddable in K1. Let A2 be the sublattice of K2 consisting of 0, 1, the meet-reducible atom, and the join-reducible coatom. Let X2 stand for the singleton consisting of the doubly reducible element of K2. For i = 1, 2, we apply the above-mentioned property of meets to prove that whenever Ki is a sublattice and Si is a retract of a slim semimodular lattice, then \(A_i \subseteq S_i\) implies that \(X_i \subseteq S_i\).
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Dedicated to Professor László Stachó on the occasion that he received the Béla Szőkefalvi-Nagy Medal of Acta Scientiarum Mathematicarum for the year 2021
This research was supported by the National Research, Development and Innovation Fund of Hungary under funding scheme K 134851.
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Czédli, G. A property of meets in slim semimodular lattices and its application to retracts. Acta Sci. Math. (Szeged) 88, 595–610 (2022). https://doi.org/10.1007/s44146-022-00040-z
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DOI: https://doi.org/10.1007/s44146-022-00040-z
Key words and phrases
- slim semimodular lattice
- planar semimodular lattice
- rectangular lattice
- retract
- retraction
- absorption property