conference title: Arithmetic groups and 3-manifolds

Arithmetic groups and 3-manifolds

A conference at University of Hagen, Germany

March 23rd-27th, 2020

UPDATE (March 12th): The University of Hagen has decided to suspend all events until (at least) April 19th due to the COVID19 outbreak which is still on the rise in Germany and in particular so in the state of North Rhine-Westphalia. Therefore we have to call off our conference.

Arithmetic groups provide a fruitful link between various areas, such as geometry, topology, representation theory and number theory. Methods from geometry and topology hinge on the fact that arithmetic groups are lattices in Lie groups, whereas the theory of automorphic forms establishes a connection to representation theory and number theory. This interplay is especially intriguing in the setting of hyperbolic 3-manifolds. Indeed many conjectures in 3-manifold theory tend to be much more accessible for hyperbolic 3-manifolds whose fundamental groups are arithmetic, and conversely such manifolds provide the simplest set-up in which some of the most exciting new phenomena in the Langlands program can be studied. This conference will bring together researchers with various backgrounds around links between number theory and 3-manifolds. Central topics of the conference are the cohomology of arithmetic groups, the relation between torsion and L²-torsion, profinite invariants of 3-manifolds, and number theoretic ramifications.

Date and place


  • Mikhail Belolipetsky (Rio de Janeiro)
  • Martin Bridson (Oxford)
  • Nathan Dunfield (Urbana-Champaign)
  • Stefan Friedl (Regensburg)
  • Andrei Jaikin (Madrid)
  • Luis Garcia (London)
  • Aditi Kar (London)
  • Dawid Kielak (Bielefeld)
  • Jasmin Matz (Copenhagen)
  • Bram Petri (Paris)
  • Aurel Page (Bordeaux)
  • Anke Pohl (Bremen)
  • Jean Raimbault (Toulouse)
  • Roman Sauer (Karlsruhe)
  • Matthew Stover (Philadelphia)
  • Lola Thompson (Oberlin)
  • Tyakal Venkataramana (Mumbai)
  • Gareth Wilkes (Cambridge)

Scientific advisory board

  • Alan Reid (Houston)
  • Thomas Schick (Göttingen)
  • Joachim Schwermer (Bonn)


  • Holger Kammeyer (Karlsruhe)
  • Steffen Kionke (Hagen)
  • Haluk Şengün (Sheffield)


The conference will take place from March 23rd at 11:00 am to March 27th at 13:00 pm. A detailed schedule will follow soon.


The deadline for funding application has passed. We ask anyone still interested in participating to contact one of the organizers by e-mail.

Directions to Hagen

Where is Hagen? Hagen is situated roughly one hour from Cologne by train. There are many airports nearby. International flights are more likely to go to Düsseldorf and Frankfurt.

Dortmund Airport: 50 minutes (By bus to Dortmund, then by train to Hagen)

Düsseldorf Airport: 60 minutes (By train, change trains in Düsseldorf or Bochum)

Köln/Bonn Airport: 75 minutes (By train, change trains in Cologne)

Frankfurt Airport: 120 minutes (By train, change trains in Cologne)

Directions to the Campus Hotel

The hotel is very close to the bus stop "FernUniversität". You can get there using the bus 515, which takes about 15 minutes from Hagen "Hauptbahnhof" (main station) to "FernUniversität" (the direction is "Hohenlimburg" or "Loxbaum"). A second option: The walking distance from the hotel to the bus stop "Polizeipräsidium" is roughly 10 minutes; the bus 514 goes to "Polizeipräsidium" (direction "Kabel" or "Bathey"). A one-way bus ticket costs 2,80 Euro. The last departure of the bus 515 at "Hauptbahnhof" is at 21:22, the last departure of bus 514 is at 21:46. If you arrive later, then it is difficult to get to the hotel and the most convenient way is to take a taxi.

These instructions also apply if one wants to arrive at the conference venue from the railway station or from the other hotels (they are all in the immediate proximity of the railway station)


For any inquiry, please contact one of the organizers:
Holger Kammeyer
Steffen Kionke
Haluk Şengün
DFG Research Training Group 2229
Asymptotic Invariants and Limits of Groups and Spaces