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In this paper we describe the space of maximal components of the character variety of surface group representations into PSp(4,R) and Sp(4,R). For every rank 2 real Lie group of Hermitian type, we construct a mapping class group invariant…

Geometric Topology · Mathematics 2019-06-05 Daniele Alessandrini , Brian Collier

We show the set of faithful representations of a closed orientable hyperbolic surface group is dense in both irreducible components of the PSL(2,K) representation variety, where K is the field of real or complex numbers, answering a…

Geometric Topology · Mathematics 2007-05-23 Jason DeBlois , Richard P. Kent

We describe a construction of Schottky type subgroups of automorphism groups of partially cyclically ordered sets. We apply this construction to the Shilov boundary of a Hermitian symmetric space and show that in this setting Schottky…

Differential Geometry · Mathematics 2018-07-17 Jean-Philippe Burelle , Nicolaus Treib

We prove that Anosov representations from a surface group to SL(3,R) are uniquely determined by their boundary maps if and only if they do not factor over a completely reducible representation. Furthermore we discuss representations not…

Geometric Topology · Mathematics 2016-12-01 Sungwoon Kim , Thilo Kuessner

A hyperbolic conjugacy class in the modular group PSL(2,Z) corresponds to a closed geodesic in the modular orbifold. Some of these geodesics virtually bound immersed surfaces, and some do not; the distinction is related to the polyhedral…

Geometric Topology · Mathematics 2020-06-04 Danny Calegari , Joel Louwsma

Let $p:\Sigma'\to\Sigma$ be a finite Galois cover, possibly branched, with Galois group $G$. We are interested in the structure of the cohomology of $\Sigma'$ as a module over $G$. We treat the cases of branched and unbranched covers…

Geometric Topology · Mathematics 2009-10-12 Thomas Koberda , Aaron Michael Silberstein

We provide the first examples of strongly dense representations of a hyperbolic 3-manifold group into $SL(4,\mathbb{R})$ and $SU(3,1)$ i.e. representations where every pair of non-commuting elements has Zariski dense image. Our examples are…

Geometric Topology · Mathematics 2024-01-17 Ricky Lee

We show for g > 6 that the second homology group of the Torelli group of a surface of genus g and 1 boundary component is generated as an Sp(2g,Z)-module by the image under the stabilization map of the second homology group of the Torelli…

Algebraic Topology · Mathematics 2011-02-03 Søren K. Boldsen , Mia Hauge Dollerup

We show that every integer in the interval $[2p\chi(\Sigma), -2p\chi(\Sigma)]$ is achieved by the signature of a rank $2p$ flat symplectic bundle over a surface with boundary $\Sigma$. When $p=1$, one can prescribe the type (elliptic,…

Group Theory · Mathematics 2024-07-16 Inkang Kim , Pierre Pansu , Xueyuan Wan

In this article we give a geometric interpretation of the Hitchin component for PSL(4,R) in the representation variety of a closed oriented surface of higher genus. We show that representations in the Hitchin component are precisely the…

Differential Geometry · Mathematics 2007-06-13 Olivier Guichard , Anna Wienhard

In the Labourie-Loftin parametrization of the Hitchin component of surface group representations into SL(3,R), we prove an asymptotic formula for holonomy along rays in terms of local invariants of the holomorphic differential defining that…

Differential Geometry · Mathematics 2026-05-21 John Loftin , Andrea Tamburelli , Michael Wolf

We study the isometry group of a globally hyperbolic spatially compact Lorentz surface. Such a group acts on the circle, and we show that when the isometry group acts non properly, the subgroups of $\mathrm{Diff}(\mathbb{S}^1)$ obtained are…

Differential Geometry · Mathematics 2014-05-28 Daniel Monclair

There is a well-known correspondence between the symplectic variety of representations of the fundamental group of a punctured Riemann surface into a compact Lie group G, with fixed conjugacy classes at the punctures, and a complex variety…

Symplectic Geometry · Mathematics 2007-05-23 Jacques Hurtubise , Lisa C. Jeffrey

We study the topology of the SU(2)-representation variety of the compact oriented surface of genus 2 with one boundary component about which the holonomy is a generator of the center of SU(2).

Symplectic Geometry · Mathematics 2021-02-08 Nan-Kuo Ho , Lisa C. Jeffrey , Paul Selick , Eugene Z. Xia

We give a new technique for constructing presentations by generators and relations for representations of groups like $SL_n(\mathbb{Z})$ and $Sp_{2g}(\mathbb{Z})$. Our results play an important role in recent work of the authors calculating…

Representation Theory · Mathematics 2025-04-02 Daniel Minahan , Andrew Putman

We characterize the representations of the fundamental group of a closed surface to $\mathrm{PSL}_2(\mathbb C)$ that arise as the holonomy of a branched complex projective structure with fixed branch divisor. In particular, we compute the…

Geometric Topology · Mathematics 2021-03-23 Thomas Le Fils

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

We study a wide range of homologically-defined representations of surface braid groups and of mapping class groups of surfaces, including the Lawrence-Bigelow representations of the classical braid groups. These representations naturally…

Geometric Topology · Mathematics 2025-09-16 Martin Palmer , Arthur Soulié

Let G be a connected, compact, semisimple Lie group. It is known that for a compact closed orientable surface $\Sigma$ of genus $l >1$, the order of the group $H^2(\Sigma,\pi_1(G))$ is equal to the number of connected components of the…

Symplectic Geometry · Mathematics 2007-05-23 Nan-Kuo Ho , Chiu-Chu Melissa Liu

For closed and oriented hyperbolic surfaces, a formula of Witten establishes an equality between two volume forms on the space of representations of the surface in a semisimple Lie group. One of the forms is a Reidemeister torsion, the…

Geometric Topology · Mathematics 2020-10-28 Michael Heusener , Joan Porti