Abstract
We investigate definability in the set of isomorphism types of finite semilattices ordered by embeddability; we prove, among other things, that every finite semilattice is a definable element in this ordered set. Then we apply these results to investigate definability in the closely related lattice of universal classes of semilattices; we prove that the lattice has no non-identical automorphisms, the set of finitely generated and also the set of finitely axiomatizable universal classes are definable subsets and each element of the two subsets is a definable element in the lattice.
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Presented by M. Valeriote.
While working on this paper, the first author (Ježek) and the second author (McKenzie) were supported by US NSF grant DMS-0604065. The first author was also supported by the institutional grant MSM0021620839 financed by MSMT and partially supported by the grant GAČR 201/05/0002.
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Ježek, J., McKenzie, R. Definability in substructure orderings, I: finite semilattices. Algebra Univers. 61, 59 (2009). https://doi.org/10.1007/s00012-009-0002-6
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DOI: https://doi.org/10.1007/s00012-009-0002-6