Rigidity of graphs in homogeneous and locally homogeneous spaces
2026 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Stelhet hos grafer i homogena och lokalt homogena rum (Swedish)
Abstract [en]
This thesis studies rigidity of graphs and hypergraphs realised in homogeneous and locally homogeneous spaces. We develop an algebraic model for describing the motions of such realisations using group-theoretic methods. The resulting structures, which we call graph-of-groups realisations, provide a unified model capable of capturing a wide range of rigidity problems. Within this model, we recover foundational results, including a necessary condition for rigidity. Using homological methods, we show that, generically, this condition is also sufficient for rigidity problems in homogeneous spaces G/H, where H is a one-dimensional and selfnormalising subgroup of a Lie group G. The resulting combinatorial conditions can be verified using the pebble game algorithm, which we analyse in novel settings. Beyond homogeneous spaces, we also study realisations of graphs in locally homogeneous spaces by interpreting these graphs as symmetric graphs in a homogeneous space. In particular, we study the minimal rigidity of symmetric graphs in the hyperbolic plane and obtain a combinatorial characterisation of minimal rigidity of graphs realised on compact orientable surfaces of genus g≥2.
Place, publisher, year, edition, pages
Umeå: Umeå University, 2026. , p. 39
Series
Doctoral thesis / Umeå University, Department of Mathematics, ISSN 1102-8300
Keywords [en]
Rigidity, hypergraph, greedoid, Lie group, homogeneous space, symmetry, graph-of-groups
National Category
Geometry Discrete Mathematics Algebra and Logic
Research subject
Mathematics
Identifiers
URN: urn:nbn:se:umu:diva-253120ISBN: 978-91-6850-059-1 (electronic)ISBN: 978-91-6850-058-4 (print)OAI: oai:DiVA.org:umu-253120DiVA, id: diva2:2059777
Public defence
2026-06-09, Lindellhallen 3, Universitetstorget 16, Umeå 907 36, 09:00 (English)
Opponent
Supervisors
2026-05-192026-05-122026-05-13Bibliographically approved
List of papers