Bram Petri


About me:
Currently, I am a post-doc in the Geometry group at the University of Bonn. My mentor is Ursula Hamenstädt.

Before this, I was a post-doctoral fellow at the Max Planck Institute for Mathematics in Bonn. Before coming to Bonn, I was a doctoral student under the supervision of Hugo Parlier at the Department of Mathematics at the University of Fribourg.

My CV and Publication list.

Mathematisches Institut der Universität Bonn
Endenicher Allee 60
D-53115 Bonn

Office: 2.003
E-mail: bpetri at


Research interests

Low dimensional geometry and topology, Hyperbolic geometry, Teichmüller and moduli spaces, Random surfaces, Random 3-manifolds, subgroup growth.


1.     Kissing numbers of closed hyperbolic manifolds
with Maxime Fortier Bourque
[arXiv version]

2. On distinct finite covers of 3-manifolds
with Stefan Friedl, JungHwan Park, Jean Raimbault and Arunima Ray
[arXiv version]

3. Counting non-commensurable hyperbolic manifolds and a bound on homological torsion
[arXiv version]

Accepted articles

12.   Universality for random surfaces in unconstrained genus
with Thomas Budzinski and Nicolas Curien
Electron. J. Combin., to appear
[arXiv version]

11. Subgroup growth of right-angled Artin and Coxeter groups
with Hyungryul Baik and Jean Raimbault
J. Lond. Math. Soc. (2), to appear.
[arXiv version]

10.   Subgroup growth of virtually cyclic right-angled Coxeter groups and their free products
with Hyungryul Baik and Jean Raimbault
Combinatorica, to appear.
[arXiv version] [Journal version]

9. Lengths of closed geodesics on random surfaces of large genus
with Maryam Mirzakhani
Comment. Math. Helv., to appear.
[arXiv version]

8. Hyperbolic surfaces with long systoles that form a pants decomposition
Proc. Amer. Math. Soc., 146 (3): 1069 - 1081, 2018.
[arXiv version] [Journal version]

7. Exponential Torsion Growth for Random 3-Manifolds
with Hyungryul Baik, David Bauer, Ilya Gekhtman, Ursula Hamenstädt, Sebastian Hensel, Thorben Kastenholz and Daniel Valenzuela
Int. Math. Res. Not. IMRN, 21: 6497 - 6534, 2018.
[arXiv version] [Journal version]

6. Poisson approximation of the length spectrum of random surfaces
with Christoph Thäle
Indiana Univ. Math. J., 67 (3): 1115 - 1141, 2018.
[arXiv version] [Journal version]

5. Mapping class group orbits of curves with self-intersections
with Patricia Cahn and Federica Fanoni
Israel J. Math., 223 (1): 53 - 74, 2018.
[arXiv version] [Journal version]

4. Graphs of Large Girth and Surfaces of Large Systole
with Alexander Walker
Math. Res. Lett., 25 (6): 1937 - 1956. 2018.
[arXiv version] [Journal version]

3. The genus of curve, pants and flip graphs
with Hugo Parlier
Discrete Comput. Geom., 59 (1): 1 - 30, 2018.
[arXiv version] [Journal version]

2. Finite length spectra of random surfaces and their dependence on genus
J. Topol. Anal., 09 (4): 649 - 688, 2017.
[arXiv version] [Journal version]

1. Random regular graphs and the systole of a random surface
J. Topol., 10 (1): 211 - 267, 2017.
[arXiv version] [Journal version]

PhD Thesis

On Random Surfaces
Written under the supervision of Hugo Parlier, University of Fribourg, 2015.

Conference organization

Geometric Group Theory in Bonn III, Jan. 31 - Feb. 1, 2019
Click here for more infomation

Geometric Group Theory in Bonn II, Dec. 3-4, 2015
Click here for more infomation


Jun. 2019     Dubrovnik IX - Topology & Dynamical Systems, Inter-University Centre Dubrovnik
Jun. 2019     Multiple Perspective on Geometric Inequalities, Centre de Recerca Matemàtica (CRM), Barcelona
15 Mar. 2019     Séminaire Teich, Université d'Aix-Marseille
05 Mar. 2019     Séminaire de Probabilités, Université de Toulouse
18 Feb. 2019     Geometry & Topology seminar, University of Glasgow
22 Jan. 2019     University of Göttingen
20 Dec. 2018     Analysis and Geometry Seminar, University of Bristol
29 Nov. 2018     Geometry Seminar, University of Barcelona
27 Nov. 2018     Séminaire Géométrie, analyse et dynamique, Université de Nice
19 Nov. 2018     Ergodic Theory Seminar, Université de Rennes
6 Nov. 2018     Séminaire Analyse, Université de Strasbourg
24-26 Sep. 2018      Representations of surface groups and beyond, Laboratoire Paul Painlevé, Université de Lille
16-20 Jul. 2018      GAGTA 2018, Korea Institute for Advanced Study
26 Mar. 2018      Geometry and Topology seminar, University of Toronto
06 Mar. 2018     Annual meeting of the DMV and the GDM, University of Paderborn
16 Nov. 2017     LKS-Seminar, University of Regensburg
15 Nov. 2017     Oberseminar Globale Analysis, University of Regensburg
11 May 2017     Geometric Topology Fair 2017, KAIST, Daejeon,
A video of this talk is available here.
24 Apr. 2017     Ergodic Theory Seminar, Université de Rennes
16 Mar. 2017     Workshop on Enumerative Geometry, IHP, Paris
23 Nov. 2016     EPF Lausanne
16 Jun. 2016     Hebrew University of Jerusalem
13 Jun. 2016 Statistics & Topology Seminar, Technion, Haifa
03 May 2016 Universität Heidelberg
20 Apr. 2016 Topology Seminar, UC Berkeley
19 Apr. 2016 Topology Seminar, Stanford University
31 Mar. 2016 MPI-Oberseminar, MPIM, Bonn
19 Mar. 2016 Special Session on Invariants of Closed Curves on Surfaces,
AMS Spring Eastern Sectional Meeting, Stony Brook University
15 Mar. 2016 Séminaire de Géométrie et Topologie, University of Toulouse
07 Dec. 2015 MPIM Toplogy Seminar , MPIM, Bonn
19 Nov. 2015 Geometry and Topology Seminar, University of Warwick
16 Nov. 2015 GT3, Université de Strasbourg
11 Nov. 2015 Universität Bielefeld
10 Nov. 2015 Geometric Analysis & Differential Geometry Short talks, MPIM, Bonn
02 Nov. 2015 Universität Bochum
04 Jun. 2015 Discrete Geometry Seminar, Freie Universität Berlin
01 Jun. 2015 Journée de géométrie, Université Paris-Est - Créteil
15 May 2015 Complex Analysis and Dynamics Seminar, Graduate Center, CUNY
12 May 2015 Stony Brook University
25 Mar. 2015 Special Year in Hyperbolic Geometry, Hunter College, CUNY
18 Feb. 2015 Graduate student seminar, Brown University
29 Jan. 2015 Boston College Geometry/Topology seminar, Boston College
20 Jan. 2015 Geometric Group Theory and Topology Seminar, Tufts University
25 Nov. 2014 Discrete math and geometry seminar , Brown University
09 Oct. 2014 Combinatorics seminar, University of Fribourg
31 May 2014 GEAR Junior Retreat, University of Michigan at Ann Arbor
21 Nov. 2013 Séminaire de Topologie et Géométrie, University of Geneva
10 Sep. 2013 Graduate Colloquium, University of Fribourg
08 Mar. 2012 Oberseminar Geometrie, University of Fribourg
14 Dec. 2011 Oberseminar Geometrie, University of Fribourg
01 Mar. 2011 Mathematical Physics Seminar, Radboud University Nijmegen
20 Dec. 2010 Mathematikon, University of Fribourg
20 Oct. 2010 Oberseminar Analysis und Spektraltheorie, TU Clausthal



2018 - 2019 / Summer:
Teichmüller Theory
Course code: V5D3 - Advanced Topics in Geometry


2018 - 2019 / Winter:
Random walks on linear groups
Course code: S4D3 - Graduate Seminar on Advanced Geometry

Simplicial volume
Course code: V5D6 - Selected Topics in Differential Geometry

2017 - 2018 / Summer:
Arithmetic groups
Course code: V5D3 - Advanced Topics in Geometry

2017 - 2018 / Winter:
Property (T)
Course code: S4D3 - Graduate Seminar on Advanced Geometry

Quantum ergodicity
Course code: S4D1 - Graduate Seminar on Differential geometry

Advanced Geometry I V4D2
Exercises week 8

2016 - 2017 / Summer:
Random methods in geometry
Course code: V5D4 - Selected Topics in Geometry

2013 - 2014 / Spring:
Assistant for Analysis IV

2013 - 2014 / Autumn:
Assistant for Analysis III

2012 - 2013 / Spring:
Assistant for Mathematical Methods in Computer Science

2012 - 2013 / Autumn:
Assistant for Mathematical Methods in Computer Science

2011 - 2012 / Spring:
Assistant for Mathematical Methods in Computer Science