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We prove that any Borel Anosov representations of a surface group into $Sp(4,\mathbb{R})$ that has maximal Toledo invariant must be Hitchin. We also prove that a representation of a surface group into $Sp(2n,\mathbb{R})$ that is…

Geometric Topology · Mathematics 2026-01-08 Colin Davalo

We develop Fenchel-Nielsen coordinates for representations of surface groups into Sp(2n,R) with maximal Toledo invariant. Analogous to classical Fenchel-Nielsen coordinates on the Teichm\"uller space they consist of a parametrization of…

Differential Geometry · Mathematics 2012-04-04 Tobias Strubel

We prove that any nonabelian, non-Fuchsian representation of a surface group into PSL(2,R) is the holonomy of a folded hyperbolic structure on the surface. Using similar ideas, we establish that any non-Fuchsian representation rho of a…

Geometric Topology · Mathematics 2016-01-20 François Guéritaud , Fanny Kassel , Maxime Wolff

We show that uniform lattices in some semi-simple groups (notably complex ones) admit Anosov surface subgroups. This result has a quantitative version: we introduce a notion, called $K$-Sullivan maps, which generalizes the notion of…

Differential Geometry · Mathematics 2020-11-18 Jeremy Kahn , François Labourie , Shahar Mozes

The Ptolemy coordinates for boundary-unipotent SL(n,C)-representations of a 3-manifold group were introduced in Garoufalidis-Thurston-Zickert inspired by the A-coordinates on higher Teichm\"{u}ller space due to Fock and Goncharov. In this…

Geometric Topology · Mathematics 2015-07-17 Stavros Garoufalidis , Matthias Goerner , Christian K. Zickert

In this paper we complete the topological description of the space of representations of the fundamental group of a punctured surface in SL(2,R) with prescribed behavior at the punctures and nonzero Euler number, following the strategy…

Differential Geometry · Mathematics 2017-05-22 Gabriele Mondello

We prove that convex-cocompact representations of finitely generated groups in the group of isometries of the infinite-dimensional hyperbolic space form an open set in the space of representations, allowing us to deform these…

Geometric Topology · Mathematics 2026-03-10 David Xu

The first part of this paper surveys several characterizations of Teichm\"uller space as a subset of the space of representation of the fundamental group of a surface into PSL(2,R). Special emphasis is put on (bounded) cohomological…

Geometric Topology · Mathematics 2011-12-06 Marc Burger , Alessandra Iozzi , Anna Wienhard

Given an oriented surface of positive genus with finitely many punctures, we classify the finite orbits of the mapping class group action on the moduli space of semisimple complex special linear two dimensional representations of the…

Geometric Topology · Mathematics 2022-06-29 Indranil Biswas , Subhojoy Gupta , Mahan Mj , Junho Peter Whang

We relate the existence of some surfaces of general type and maximal Albanese dimension to the existence of some monodromy representations of the braid group $\mathsf{B}_2(C_2)$ in the symmetric group $\mathsf{S}_n$. Furthermore, we compute…

Algebraic Geometry · Mathematics 2018-04-09 Francesco Polizzi

We give a geometric interpretation of Fock--Goncharov positivity and show that bending deformations of Fuchsian representations stabilize a uniform Finsler quasi-convex disk in the symmetric space $\mathrm{PSL}_d(\mathbb…

Differential Geometry · Mathematics 2025-07-03 Pierre-Louis Blayac , Ursula Hamenstädt , Théo Marty

Braid groups are an important and flexible tool used in several areas of science, such as Knot Theory (Alexander's theorem), Mathematical Physics (Yang-Baxter's equation) and Algebraic Geometry (monodromy invariants). In this note we will…

Algebraic Geometry · Mathematics 2019-05-10 Francesco Polizzi

We produce a complete list of group presentations for singly-cusped Bianchi groups, $PSL_2 (\mathcal{O}_d)$ where $\mathcal{O}_d$ is the ring of integers for $\mathbb{Q}(\sqrt{d})$ and $d$ is -1, -2, -3, -7, -11, -19, -43, -67, or -163. To…

Group Theory · Mathematics 2025-08-15 Tanner Reese

We characterize helix surfaces (constant angle surfaces) in the special linear group $\mathrm{SL}(2,\r)$. In particular, we give an explicit local description of these surfaces in terms of a suitable curve and a 1-parameter family of…

Differential Geometry · Mathematics 2015-01-28 S. Montaldo , I. I. Onnis , A. Passos Passamani

We show that among antipodal $2d$-point configurations on the sphere $S^{d-1}$ in $\mathbb R^d$, the set of vertices of a regular cross-polytope inscribed in $S^{d-1}$ uniquely solves the best-covering problem (this is new for $d\geq 5$)…

Optimization and Control · Mathematics 2022-10-25 Sergiy Borodachov

We study the geometry of hyperconvex representations of hyperbolic groups in ${\rm PSL}(d,\mathbb{C})$ and establish two structural results: a group admitting a hyperconvex representation is virtually isomorphic to a Kleinian group, and its…

Geometric Topology · Mathematics 2025-07-30 James Farre , Beatrice Pozzetti , Gabriele Viaggi

Let $S$ be a closed surface of genus $g \geq 2$ and let $\rho$ be a maximal $\mathrm{PSL}(2, \mathbb{R}) \times \mathrm{PSL}(2, \mathbb{R})$ surface group representation. By a result of Schoen, there is a unique $\rho$-equivariant minimal…

Differential Geometry · Mathematics 2019-10-17 Charles Ouyang

We give a complete characterization of the holonomies of strictly convex cusps and of round cusps in convex projective geometry. We build families of generalized cusps of non-maximal rank associated to each strictly convex or round cusp. We…

Geometric Topology · Mathematics 2025-12-02 Balthazar Fléchelles

Given a $\vartheta$-Anosov representation into a real reductive group $G$, we construct a natural resonance spectrum associated with the representation. This spectrum is a complex analytic variety of codimension $1$ in…

Representation Theory · Mathematics 2026-03-26 Yannick Guedes Bonthonneau , Thibault Lefeuvre , Tobias Weich

We describe a connected component of the space of conjugacy classes of representations of the modular group $\mathrm{PSL}_2(\mathbb{Z})$ into the isometry group of the symmetric space $\mathrm{SL}_3(\mathbb{R})/\mathrm{SO}(3)$. This…

Geometric Topology · Mathematics 2026-01-27 Joan Porti