{ "id": "2008.10800", "version": "v1", "published": "2020-08-25T03:39:47.000Z", "updated": "2020-08-25T03:39:47.000Z", "title": "Virtually nilpotent groups with finitely many orbits under automorphisms", "authors": [ "Raimundo Bastos", "Alex C. Dantas", "Emerson de Melo" ], "categories": [ "math.GR" ], "abstract": "Let $G$ be a group. The orbits of the natural action of $\\Aut(G)$ on $G$ are called \"automorphism orbits\" of $G$, and the number of automorphism orbits of $G$ is denoted by $\\omega(G)$. Let $G$ be a virtually nilpotent group such that $\\omega(G)< \\infty$. We prove that $G = K \\rtimes H$ where $H$ is a torsion subgroup and $K$ is a torsion-free nilpotent radicable characteristic subgroup of $G$. Moreover, we prove that $G^{'}= D \\times \\Tor(G^{'})$ where $D$ is a torsion-free nilpotent radicable characteristic subgroup. In particular, if the maximum normal torsion subgroup $\\tau(G)$ of $G$ is trivial, then $G^{'}$ is nilpotent.", "revisions": [ { "version": "v1", "updated": "2020-08-25T03:39:47.000Z" } ], "analyses": { "subjects": [ "20E22", "20E36" ], "keywords": [ "virtually nilpotent group", "torsion-free nilpotent radicable characteristic subgroup", "automorphism orbits", "maximum normal torsion subgroup", "natural action" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable" } } }