English

Pappus Theorem, Schwartz Representations and Anosov Representations

Dynamical Systems 2018-02-07 v2 Geometric Topology Representation Theory

Abstract

In the paper "Pappus's theorem and the modular group", R. Schwartz constructed a 2-dimensional family of faithful representations ρΘ\rho_\Theta of the modular group PSL(2,Z)\mathrm{PSL}(2,\mathbb{Z}) into the group G\mathscr{G} of projective symmetries of the projective plane via Pappus Theorem. The image of the unique index 2 subgroup PSL(2,Z)o\mathrm{PSL}(2,\mathbb{Z})_o of PSL(2,Z)\mathrm{PSL}(2,\mathbb{Z}) under each representation ρΘ\rho_\Theta is in the subgroup PGL(3,R)\mathrm{PGL}(3,\mathbb{R}) of G\mathscr{G} and preserves a topological circle in the flag variety, but ρΘ\rho_\Theta is not Anosov. In her PhD Thesis, V. P. Val\'erio elucidated the Anosov-like feature of Schwartz representations: For every ρΘ\rho_\Theta, there exists a 1-dimensional family of Anosov representations ρΘε\rho^\varepsilon_{\Theta} of PSL(2,Z)o\mathrm{PSL}(2,\mathbb{Z})_o into PGL(3,R)\mathrm{PGL}(3,\mathbb{R}) whose limit is the restriction of ρΘ\rho_\Theta to PSL(2,Z)o\mathrm{PSL}(2,\mathbb{Z})_o. In this paper, we improve her work: For each ρΘ\rho_\Theta, we build a 2-dimensional family of Anosov representations of PSL(2,Z)o\mathrm{PSL}(2,\mathbb{Z})_o into PGL(3,R)\mathrm{PGL}(3,\mathbb{R}) containing ρΘε\rho^\varepsilon_{\Theta} and a 1-dimensional subfamily of which can extend to representations of PSL(2,Z)\mathrm{PSL}(2,\mathbb{Z}) into G\mathscr{G}. Schwartz representations are therefore, in a sense, the limits of Anosov representations of PSL(2,Z)\mathrm{PSL}(2,\mathbb{Z}) into G\mathscr{G}.

Keywords

Cite

@article{arxiv.1610.04049,
  title  = {Pappus Theorem, Schwartz Representations and Anosov Representations},
  author = {Thierry Barbot and Gye-Seon Lee and Viviane Pardini Valério},
  journal= {arXiv preprint arXiv:1610.04049},
  year   = {2018}
}

Comments

32 pages, 16 figures, to appear at Annales de l'Institut Fourier

R2 v1 2026-06-22T16:19:43.223Z