
Journal of Lie Theory 30 (2020), No. 1, 171178 Copyright Heldermann Verlag 2020 Subsemigroups of Nilpotent Lie Groups Herbert Abels Fakultät für Mathematik, Universität Bielefeld, 33501 Bielefeld, Germany abels@math.unibielefeld.de Ernest B. Vinberg Chair of Algebra, Dept. of Mechanics and Mathematics, Moscow State University, Moscow 119991, Russia evinberg@gmail.com For a closed subsemigroup S of a simply connected nilpotent Lie group G, we prove that either S is a subgroup, or there is an epimorphism f from G to the reals R such that f(s) ≥ 0 for all s of S. Keywords: Topological group, semigroup, nilpotent Lie group. MSC: 22E25, 20M20. [ Fulltextpdf (100 KB)] for subscribers only. 