Sami Douba's Webpage

I am an assistant (Akademischer Rat auf Zeit) in the group of Ursula Hamenstädt at the University of Bonn. Broadly speaking, I am interested in representations of finitely generated infinite groups from the perspectives of geometry, topology, dynamics, and commutative algebra.

For the Winter 2025 semester, I will be leading a graduate seminar on the fundamentals of homogeneous dynamics. For more details, see here.

For the first five months of 2026, I will be a postdoc within the SLMath program Geometry and Dynamics for Discrete Subgroups of Higher Rank Lie Groups. Teddy Weisman, Brandis Whitfield, and I are organizing a satellite event: the log cabin workshop A Kleinian eye on mapping class groups and higher-rank Lie groups.

Previously, I was a postdoc at the Institut des Hautes Études Scientifiques, under the mentorship of Fanny Kassel. I completed my Ph.D. in 2022 at McGill University, where I was supervised by Piotr Przytycki and Dmitry Jakobson.

Here are some handwritten notes from a mini-course on reflection groups that I gave at the Institut Henri Poincaré within the program T2-2025 Higher rank geometric structures.

Here is my CV.

Email: douba at math dot uni-bonn dot de

Publications and preprints

• On reflections of congruence hyperbolic manifolds, with F. Vargas Pallete, preprint.
• Ping-pong in the projective plane over a nonarchimedean field, with D. Kubrak and K. Tsouvalas, submitted.
• Zariski-closures of linear reflection groups, with J. Audibert, G.-S. Lee, and L. Marquis, submitted.
• Convex cocompact groups in real hyperbolic spaces with limit set a Pontryagin sphere, with G.-S. Lee, L. Marquis, and L. Ruffoni, submitted.
• Density of systoles of hyperbolic manifolds, with J. Huang, C. R. Math. (2024).
• Systoles of hyperbolic hybrids, Tunis. J. Math. (2025).
• Infinitely many commensurability classes of compact Coxeter polyhedra in H⁴ and H⁵, with N. Bogachev, and J. Raimbault, Adv. Math. (2024).
• Cubulated hyperbolic groups admit Anosov representations, with B. Fléchelles, T. Weisman, and F. Zhu, to appear in Geom. Topol.
• On regular subgroups of SL₃(R), with K. Tsouvalas, submitted.
• Geometric and arithmetic properties of Löbell polyhedra, with N. Bogachev, to appear in Alg. Geom. Top.
• A novel witness to incoherence of SL₅(Z), Proc. Am. Math. Soc (2024).
• Anosov groups that are indiscrete in rank one, with K. Tsouvalas, Int. Math. Res. Not. (2024).
• A hyperbolic lattice in each dimension with Zariski-dense surface subgroups, Proc. Am. Math. Soc (2023).
• Thin right-angled Coxeter groups in some uniform arithmetic lattices, Bull. London Math. Soc (2022).
• Proper CAT(0) actions of unipotent-free linear groups, J. Inst. Math. Jussieu (2025).
• Virtually unipotent curves in some non-NPC graph manifolds, Internat. J. Algebra Comput. (2023).
• 2-Systems of arcs on spheres with prescribed endpoints, Mich. Math. J (2021).

• Unipotents and graph manifold groups, Ph.D. thesis (defended July 2022).