Ursula Hamenstädt
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
Ursula Hamenstädt has a total of 25 co-authors. Here are the top co-authors by number of shared publications:
- Sebastian Hensel
Department Mathematisches Institut, LMU München, Munich, Germany
10 shared publications - Ben Weinkove
Northwestern University, Evanston, USA
3 shared publications Gérard Besson
Université de Grenoble, Saint-Martin-d’Hères, France
3 shared publications- Hyungryul Baik
Department of Mathematical Sciences, KAIST, Daejeon, South Korea
3 shared publications Michael Kapovich
University of California at Davis, USA
3 shared publicationsEndenicher Allee 60 Mathematisches Institut der Rheinischen Friedrich-Wilhelms-Universität Bonn
2 shared publications
Latest Publications
- 14 October 2026
- Published by European Mathematical Society - EMS - Publishing House GmbH
- p. 143-169
Submanifold projections and hyperbolicity in Out(𝘍ₙ)
The free splitting graph of a free group $F\_{n}$ with $n\geq 2$ generators is a hyperbolic $\mathrm{Out}(F\_{n})$-graph which has a geometric realization as a sphere graph in the connected sum of $n$ copies of $S^{1}\times S^{2}$. We use this realization to construct submanifold projections of the free splitting graph into the free splitting graphs of proper free factors. This is used to construct, for $n\geq 3$, a new hyperbolic $\mathrm{Out}(F\_{n})$-graph. If $n=3$, then every exponentially growing element acts on this graph with positive translation length.- 14 October 2026
- Published by European Mathematical Society - EMS - Publishing House GmbH
- p. 143-169
Submanifold projections and hyperbolicity in Out(𝘍ₙ)
The free splitting graph of a free group $F\_{n}$ with $n\geq 2$ generators is a hyperbolic $\mathrm{Out}(F\_{n})$-graph which has a geometric realization as a sphere graph in the connected sum of $n$ copies of $S^{1}\times S^{2}$. We use this realization to construct submanifold projections of the free splitting graph into the free splitting graphs of proper free factors. This is used to construct, for $n\geq 3$, a new hyperbolic $\mathrm{Out}(F\_{n})$-graph. If $n=3$, then every exponentially growing element acts on this graph with positive translation length.- Open Access
- 3 August 2026
- Published by Wiley in Proceedings of the London Mathematical Society
- Vol. 133 (2)
An EZ‐structure for the mapping class group
We construct a boundary for the mapping class group of a surface of finite type. The action of on this boundary is minimal, strongly proximal and topologically free. The boundary is the boundary of an ‐structure for .
- 3 August 2026
- Published by Wiley in Proceedings of the London Mathematical Society
- Vol. 133 (2)
Open AccessAn EZ‐structure for the mapping class group
We construct a boundary for the mapping class group of a surface of finite type. The action of on this boundary is minimal, strongly proximal and topologically free. The boundary is the boundary of an ‐structure for .
- 29 May 2026
- Published by Wiley in Bulletin of the London Mathematical Society
- Vol. 58 (6)
On random walks on the mapping class group
We define an electrification of the curve graph of a surface of finite type and use it to identify the Poisson boundary of a random walk on the mapping class group of with some logarithmic moment condition as a stationary measure on the space of minimal and maximal geodesic laminations on , equipped with the Hausdorff topology.
- 29 May 2026
- Published by Wiley in Bulletin of the London Mathematical Society
- Vol. 58 (6)
On random walks on the mapping class group
We define an electrification of the curve graph of a surface of finite type and use it to identify the Poisson boundary of a random walk on the mapping class group of with some logarithmic moment condition as a stationary measure on the space of minimal and maximal geodesic laminations on , equipped with the Hausdorff topology.
- Open Access
Hitchin grafting representations I: Geometry
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 $\mathrm{PSL}_d(\mathbb R)/\mathrm{PSO}(d)$.Open AccessHitchin grafting representations I: Geometry
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 $\mathrm{PSL}_d(\mathbb R)/\mathrm{PSO}(d)$. - 19 February 2025
- Published by European Mathematical Society - EMS - Publishing House GmbH in Groups, Geometry, and Dynamics
$L^{p}$-cohomology for groups of isometries of Hadamard spaces
We show that a discrete group \Gamma which admits a non-elementary isometric action on a Hadamard manifold of bounded negative curvature admits an isometric action on an L^{p} -space V for some p>1 with H^{1}(\Gamma,V)\not=0 .
- 19 February 2025
- Published by European Mathematical Society - EMS - Publishing House GmbH in Groups, Geometry, and Dynamics
$L^{p}$-cohomology for groups of isometries of Hadamard spaces
We show that a discrete group \Gamma which admits a non-elementary isometric action on a Hadamard manifold of bounded negative curvature admits an isometric action on an L^{p} -space V for some p>1 with H^{1}(\Gamma,V)\not=0 .
- 5 June 2024
- Published by American Mathematical Society (AMS) in Proceedings of the American Mathematical Society
- Vol. 152 (8) , 3599-3603
Actions of finitely generated groups on compact metric spaces
Let Γ \Gamma be a finitely generated group which admits an action by homeomorphisms on a metrizable space X X . We show that there is a metric on X X defining the original topology such that for this metric, the action is by bi-Lipschitz transformations.
- 5 June 2024
- Published by American Mathematical Society (AMS) in Proceedings of the American Mathematical Society
- Vol. 152 (8) , 3599-3603
Actions of finitely generated groups on compact metric spaces
Let Γ \Gamma be a finitely generated group which admits an action by homeomorphisms on a metrizable space X X . We show that there is a metric on X X defining the original topology such that for this metric, the action is by bi-Lipschitz transformations.
- Open AccessSubmanifold projections and hyperbolicity in ${\rm Out}(F_n)$The free splitting graph of a free group $F_n$ with $n\geq 2$ generators is a hyperbolic ${\rm Out}(F_n)$-graph which has a geometric realization as a sphere graph in the connected sum of $n$ copies of $S^1\times S^2$. We use this realization to construct submanifold projections of the free splitting graph into the free splitting graphs of proper free factors. This is used to construct for $n\geq 3$ a new hyperbolic ${\rm Out}(F_n)$-graph. If $n=3$, then every exponentially growing element acts on this graph with positive translation length.Open AccessSubmanifold projections and hyperbolicity in ${\rm Out}(F_n)$The free splitting graph of a free group $F_n$ with $n\geq 2$ generators is a hyperbolic ${\rm Out}(F_n)$-graph which has a geometric realization as a sphere graph in the connected sum of $n$ copies of $S^1\times S^2$. We use this realization to construct submanifold projections of the free splitting graph into the free splitting graphs of proper free factors. This is used to construct for $n\geq 3$ a new hyperbolic ${\rm Out}(F_n)$-graph. If $n=3$, then every exponentially growing element acts on this graph with positive translation length.
- 20 February 2024
- Published by Walter de Gruyter GmbH in Journal für die reine und angewandte Mathematik (Crelles Journal)
- Vol. 2024 (809) , 41-89
Periodic orbits in the thin part of strata
Let S be a closed oriented surface of genus g ≥ 0 {g\geq 0} with n ≥ 0 {n\geq 0} punctures and 3 g - 3 + n ≥ 5 {3g-3+n\geq 5} . Let 𝒬 {{\mathcal{Q}}} be a connected component of a stratum in the moduli space 𝒬 ( S ) {{\mathcal{Q}}(S)} of area one meromorphic quadratic differentials on S with n simple poles at the punctures or in the moduli space ℋ ( S ) {{\mathcal{H}}(S)} of abelian differentials on S if n = 0 {n=0} . For a compact subset K of 𝒬 ( S ) {{\mathcal{Q}}(S)} or of ℋ ( S ) {{\mathcal{H}}(S)} , we show that the asymptotic growth rate of the number of periodic orbits for the Teichmüller flow Φ t {\Phi^{t}} on 𝒬 {{\mathcal{Q}}} which are entirely contained in 𝒬 - K {{\mathcal{Q}}-K} is at least h ( 𝒬 ) - 1 {h({\mathcal{Q}})-1} , where h ( 𝒬 ) > 0 {h({\mathcal{Q}})>0} is the complex dimension of ℝ + 𝒬 {\mathbb{R}^{+}{\mathcal{Q}}} .- 20 February 2024
- Published by Walter de Gruyter GmbH in Journal für die reine und angewandte Mathematik (Crelles Journal)
- Vol. 2024 (809) , 41-89
Periodic orbits in the thin part of strata
Let S be a closed oriented surface of genus g ≥ 0 {g\geq 0} with n ≥ 0 {n\geq 0} punctures and 3 g - 3 + n ≥ 5 {3g-3+n\geq 5} . Let 𝒬 {{\mathcal{Q}}} be a connected component of a stratum in the moduli space 𝒬 ( S ) {{\mathcal{Q}}(S)} of area one meromorphic quadratic differentials on S with n simple poles at the punctures or in the moduli space ℋ ( S ) {{\mathcal{H}}(S)} of abelian differentials on S if n = 0 {n=0} . For a compact subset K of 𝒬 ( S ) {{\mathcal{Q}}(S)} or of ℋ ( S ) {{\mathcal{H}}(S)} , we show that the asymptotic growth rate of the number of periodic orbits for the Teichmüller flow Φ t {\Phi^{t}} on 𝒬 {{\mathcal{Q}}} which are entirely contained in 𝒬 - K {{\mathcal{Q}}-K} is at least h ( 𝒬 ) - 1 {h({\mathcal{Q}})-1} , where h ( 𝒬 ) > 0 {h({\mathcal{Q}})>0} is the complex dimension of ℝ + 𝒬 {\mathbb{R}^{+}{\mathcal{Q}}} .- Open Access
Symbolic dynamics for the Teichmueller flow
Let Q be a component of a stratum of abelian or quadratic differentials on an oriented surface of genus $g\geq 0$ with $m\geq 0$ punctures and $3g-3+m\geq 2$. We construct a subshift of finite type $(\Omega,\sigma)$ and a Borel suspension of $(\Omega,\sigma)$ which admits a finite-to-one semi-conjugacy into the Teichmueller flow $\Phi^t$ on Q. This is used to show that the $\Phi^t$-invariant Lebesgue measure on Q is the unique measure of maximal entropy.Open AccessSymbolic dynamics for the Teichmueller flow
Let Q be a component of a stratum of abelian or quadratic differentials on an oriented surface of genus $g\geq 0$ with $m\geq 0$ punctures and $3g-3+m\geq 2$. We construct a subshift of finite type $(\Omega,\sigma)$ and a Borel suspension of $(\Omega,\sigma)$ which admits a finite-to-one semi-conjugacy into the Teichmueller flow $\Phi^t$ on Q. This is used to show that the $\Phi^t$-invariant Lebesgue measure on Q is the unique measure of maximal entropy. - Open Access
Periodic orbits in the thin part of strata
Let S be a closed oriented surface of genus $g\geq 0$ with $n\geq 0$ punctures and $3g-3+n\geq 5$. Let $Q$ be a connected component of a stratum in the moduli space Q(S) of area one meromorphic quadratic differentials on S with n simple poles at the punctures or in the moduli space H(S) of abelian differentials on S if n=0. For a compact subset K of Q(S) or of H(S), we show that the asymptotic growth rate of the number of periodic orbits for the Teichmueller flow on Q which are entirely contained in Q-K is at least h(Q)-1 where h(Q)>0 is the complex dimension of Q.Open AccessPeriodic orbits in the thin part of strata
Let S be a closed oriented surface of genus $g\geq 0$ with $n\geq 0$ punctures and $3g-3+n\geq 5$. Let $Q$ be a connected component of a stratum in the moduli space Q(S) of area one meromorphic quadratic differentials on S with n simple poles at the punctures or in the moduli space H(S) of abelian differentials on S if n=0. For a compact subset K of Q(S) or of H(S), we show that the asymptotic growth rate of the number of periodic orbits for the Teichmueller flow on Q which are entirely contained in Q-K is at least h(Q)-1 where h(Q)>0 is the complex dimension of Q.