,
Harald Woracek
Creative Commons Attribution 4.0 International license
Convex semilattices are algebras that are at the same time a convex algebra and a semilattice, together with a distributivity axiom. These algebras have attracted some attention in the last years as suitable algebras for probability and nondeterminism, in particular by being the Eilenberg-Moore algebras of the nonempty finitely-generated convex subsets of the distributions monad. A convex semilattice is cancellative if the underlying convex algebra is cancellative. Cancellative convex algebras have been characterized by M. H. Stone and by H. Kneser: A convex algebra is cancellative if and only if it is isomorphic to a convex subset of a vector space (with canonical convex algebra operations). We prove an analogous theorem for convex semilattices: A convex semilattice is cancellative if and only if it is isomorphic to a convex subset of a Riesz space, i.e., a lattice-ordered vector space (with canonical convex semilattice operations).
@InProceedings{sokolova_et_al:LIPIcs.CALCO.2025.12,
author = {Sokolova, Ana and Woracek, Harald},
title = {{Cancellative Convex Semilattices}},
booktitle = {11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)},
pages = {12:1--12:15},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-383-6},
ISSN = {1868-8969},
year = {2025},
volume = {342},
editor = {C\^{i}rstea, Corina and Knapp, Alexander},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2025.12},
URN = {urn:nbn:de:0030-drops-235714},
doi = {10.4230/LIPIcs.CALCO.2025.12},
annote = {Keywords: convex semilattice, cancellativity, Riesz space}
}