English

The space of properly-convex structures

Geometric Topology 2020-09-15 v1

Abstract

Suppose GG is finitely generated group and C(G)\mathcal{C}(G) consists of all ρ:GPGL(n+1,R)\rho:G\to\operatorname{PGL}(n+1,\mathbb{R}) for which there exists a properly convex set in RPn\mathbb{R}\mathbb{P}^n that is preserved by ρ(G)\rho(G). Then the image of C(G)\mathcal{C}(G) is closed in the character variety. Suppose GG does not contain an infinite, normal, abelian subgroup and D(G)C(G)\mathcal{D}(G)\subset\mathcal{C}(G) is the subset of holonomies of properly-convex nn-manifolds with fundamental group GG. Then the image D(G)\mathcal{D}(G) is closed in the character variety. If MM is the interior of a compact nn-manifold and G=π1MG=\pi_1M is as above, and either MM is closed, or π1M\pi_1M contains a subgroup of infinite index isomorphic to Zn1\mathbb{Z}^{n-1}, then D(G)\mathcal{D}(G) is closed. If, in addition, MM is the interior of a compact manifold NN such that every component of N\partial N is π1\pi_1-injective, and finitely covered by a torus, then every element of D(G)\mathcal{D}(G) is the holonomy of a properly-convex structure on MM, and D(G)\mathcal{D}(G) is a union of connected components of a semi-algebraic set.

Keywords

Cite

@article{arxiv.2009.06568,
  title  = {The space of properly-convex structures},
  author = {Daryl Cooper and Stephan Tillmann},
  journal= {arXiv preprint arXiv:2009.06568},
  year   = {2020}
}
R2 v1 2026-06-23T18:31:53.663Z