G. Czédli

activity

20122022

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Showing 2018Show all

4 papers · 1 filter

math.RA2018

Lattices with many congruences are planar

Gábor Czédli

Let $L$ be an $n$ -element finite lattice. We prove that if $L$ has strictly more than $2^{n - 5}$ congruences, then $L$ is planar. This result is sharp, since for each natural number…

math.RA2018

Symmetric embeddings of free lattices into each other

Gábor Czédli, Gergő Gyenizse, Ádám Kunos

By a 1941 result of Ph. M. Whitman, the free lattice FL(3) on three generators includes a sublattice $S$ that is isomorphic to the lattice FL( $ω$ )=FL( $ℵ_{0}$ ) generated freely b…

math.MG2018

Circles and crossing planar compact convex sets

Gábor Czédli

Let $K_{0}$ be a compact convex subset of the plane $R^{2}$ , and assume that whenever $K_{1} \subseteq R^{2}$ is congruent to $K_{0}$ , then $K_{0}$ and $K_{1}$ are not crossing in…

math.RA2018

Finite semilattices with many congruences

Gábor Czédli

For an integer $n \geq 2$ , let NCSL $(n)$ denote the set of sizes of congruence lattices of $n$ -element semilattices. We find the four largest numbers belonging to NCSL $(n)$ , provide…