Roman Sauer

Upcoming events

• Topology and Groups, Berlin, June 25-29
• Blockseminar Geometrische Gruppentheorie, Münster, September 24-27
• Minerva summer school on flows on homogeneous spaces, Haifa, September 2-7
• "Action now"-Seminar, Berlin, October 11-12

Lehre

SS 2012:

• Vorlesung: Topologie II (Mi 8:30-10:00 in M104 und Fr 10:15-12:00 in M 104)
  
• Bachelorseminar (Fr 12:30-14:00 in M 102)
• Seminar: Gebäude (Do 12-14 in M 104)
• Oberseminar: Globale Analysis und Geometrie (Mi 10-12 in M103)

WS 2011:

• Vorlesung: Topologie I (Mi 8-10 in M104 und Fr 10-12 in M 104)
  
• Seminar: Liegruppen und ihre Darstellungen (Do 14-16 in M 102)
• Seminar: Differentialtopologie (Di 12-14 in M 101)
• Oberseminar: Stable cohomology of arithmetic groups after Borel (Fr 8-10 in M006) (Programm)
• Oberseminar: Globale Analysis und Geometrie (Mi 10-12 in M103)

Publications

Research papers:

• On the growth of Betti numbers in p-adic analytic towers
  joint with Nicolas Bergeron and Peter Linnell and Wolfgang Lück
  [arXiv:1204.3298]
  
• Integrable measure equivalence and rigidity of hyperbolic lattices
  joint with Uri Bader and Alex Furman
  [arXiv:1006.5193]
  
• Efficient subdivision in hyperbolic groups and applications
  joint with Uri Bader and Alex Furman
  to appear in Groups, Geometry, and Dynamics
  [arXiv:1003.1562]
  
• Euler characteristics of categories and homotopy colimits
  joint with Tom Fiore and Wolfgang Lück
  Documenta Math. 16 (2011), 301--354
  [arXiv:1007.3868]  [Journal]  [MR2804514]
  
• Spectral distribution and L²-isoperimetric profile of Laplace operators on groups
  joint with Alexander Bendikov and Christophe Pittet
  Mathematische Annalen (in press)
  [arXiv:0901.0271]  [Journal]
  
• Finiteness obstructions and Euler characteristics of categories
  joint with Tom Fiore and Wolfgang Lück
  Advances in Mathematics, Volume 226, Issue 3, 2011, 2371–2469
  [arXiv:0908.3417]  [Journal]   [MR2739781]
  
• The limit of F_p-Betti numbers of a tower of finite covers with amenable fundamental groups
  joint with Peter Linnell and Wolfgang Lück
  Proc. Amer. Math. Soc. 139 (2011), 421-434
  [arXiv:1003.0434]  [Journal]  [MR2736326]
  
• L²-torsion, the measure-theoretic determinant conjecture, and uniform measure equivalence
  joint with and Wolfgang Lück and Christian Wegner
  Journal of Topology and Analysis, Volume 2, Issue 2, 2010, 145-171
  [arXiv:0903.2925]  [Journal]  [MR2652905]
  
• A spectral sequence to compute L²-Betti numbers of groups and groupoids
  joint with Andreas Thom
  Journal of the London Mathematical Society, Volume 81, Number 3, 2010, 747-773
  [arXiv:0707.0906]  [Journal]  [MR2650795 ]
  
• Degree theorems and Lipschitz simplicial volume for non-positively curved manifolds of finite volume
  joint with Clara Löh
  Journal of Topology, Volume 2, Number 1, 2009, 193-225
  [arXiv:0710.1635]  [Journal]  [MR2499443]
  
• Simplicial Volume of Hilbert modular varieties
  joint with Clara Löh
  Commentarii Mathematici Helvetici, Volume 84, Issue 3, 2009, 457-470
  [arXiv:0706.3904] [Journal]  [MR2507250]
  
• Amenable covers, volume and L²-Betti numbers of aspherical manifolds
  J. Reine Angew. Math (Crelle's Journal), Issue 636, November 2009, 47-92
  [math.AT/0605627] [Journal]  [MR2572246 ]
  
• Homological invariants and quasi-isometry
  Geom. Funct. Anal. (GAFA), Volume 16, Number 2, 2006, 476–515
  [math.AT/0312129]  [Journal]  [MR2231471]
  
• L²-Betti numbers of discrete measured groupoids
  Internat. J. Algebra Comput. 15 (2005), no. 5-6, 1169–1188
  [math.AT/0312411]  [Journal]  [MR2197826]
  
• Power series over the group ring of a free group and applications to Novikov-Shubin invariants
  Proceedings of the School High-Dimensional Manifold Topology, Trieste, 2003.
  [pdf]  [MR2048733]
  

Expository papers:

• Homotopy invariance of almost flat Betti numbers
  joint with Thomas Schick
  Enseign. Math. (2) 54 (2008), no. 1-2 (Guido's book of conjectures)
  [pdf] [MR2454697]
  
• Volume and L²-Betti numbers of aspherical manifolds
  Proceedings of the Courant Colloquium Göttingen 2007 (ISBN 3-978-3-940344-56-4)
  [Online edition] [pdf] 
  

Organized conferences and schools

• Minerva summer school on flows on homogeneous spaces at the Technion in Haifa, September 2012
  Other organizers: Uri Bader and Francoise Dal'Bo

• AIM Square program on “New Horizons for Simplicial Volume and the Barycenter Method”
  Other organizers: Michelle Bucher and Chris Connell and Jean Lafont and Ben Schmidt

• Summer school Geometry and Rigidity of Groups at the University of Münster, August 2009.
  Other organizers: Arthur Bartels and Wolfgang Lück
• Research seminar on Analysis on metric spaces organized with Shmuel Weinberger at the University of Chicago, Winter 2008.
• Workshop L²-Invariants, Measure Theory and Geometric Group Theory at the University of Münster, March 2004
  Other organizers: Damien Gaboriau, Wolfgang Lück, Andrzej Zuk.
  (Downlad the conference booklet)

Invited presentations

• Mittag-Leffler institute, Stockholm, Geometric and Analytic Aspects of Group Theory, April 2012
• Beit Hatfutsot, Tel Aviv, Transcending Tradition -- Jewish Mathematicians in German-Speaking Academic Culture, November 2011
• Technion, Haifa, Conference on geometric group theory, June 2011
• University of Bonn, 14th NRW Topology meeting, November 2011
• Technion, Haifa, Colloquium, June 2010
  [Slides]
• Technion, Haifa, Geometry Seminar, June 2010
• ETH Zürich, Algebra and Topology Seminar, March 2010
• ETH Zürich, Geometry Seminar, March 2010
• University of Copenhagen, Workshop: Von Neumann algebras and group actions, February 2010
• University of Regensburg, Kolloquium, December 2009
  [Slides]
• Hausdorff Institute Bonn, Workshop: Rigidity in cohomology, K-theory, geometry and ergodic theory, November 2009
• University of Osnabrück, Kolloquium, October 2009
• University of Göttingen, Lecture series on "measurable group theory as a tool in geometry", August 2009
  [Notes by Anke Pohl]
• WWU Münster, Habilitationskolloquium, July 2009
• University of Illinois at Chicago, Geometry, Topology, and Dynamics Seminar, March 2009
• University of Regensburg, Kolloquium, March 2009
• University of Regensburg, Kolloquium des Kepler-Forschungszentrums, November 2008
• LMU München, Differentialtopologie-Seminar, November 2008
• MFO Oberwolfach, Workshop on von Neumann algebras and ergodic theory of group actions, November 2008
• University of Stuttgart, Kolloquium, October 2008
  [Slides]
• MFO Oberwolfach, Topology workshop, September 2008
• Banff International Research Station, Topics in von Neumann algebras, March 2008
  [Slides] [Handout]
• University of Michigan, Geometry seminar, February 12, 2008
• Courant Research Center Göttingen, Courant-Colloquium "Göttingen trends in Mathematics", October 2007
  [Slides] [Extended notes]
• WWU Münster, Oberseminar Topologie, October 2007
• Banff International Research Station, Topological and geometric rigidity, July 2007
  [Slides]
• Binghamton University,Topology seminar, April 2007
• University of Urbana-Champaign, Seminar, April 2007
• Banff International Research Station, Topology, February 2007
• Ohio State University, Seminar, February 2007
• University of Illinois at Chicago, Geometry, Topology, and Dynamics Seminar, November 2006
• University of Karlsruhe, Conference on "Geometry and algebra of solvable groups", October 2006
• MPI Bonn, Activity on Geometry and Group Theory, July 2006
• MPI Bonn, Oberseminar Topologie, July 2006
• CRM Montreal Conference on geometric group theory, July 2006
• MFO Oberwolfach, Topological and Geometric Methods in Group Theory, April 2006
• University of South Alabama, G3-conference, March 2006
• University of Chicago, Topology/Geometry Seminar, March 2006
• LMU München, Differentialtopologie-Seminar, January 2006
• Nashville, Third Annual Spring Institute on Noncommutative Geometry and Operator Algebras, May 2005
• University of Tel-Aviv, Seminar, May 2005
• Hebrew University Jerusalem, Seminar, May 2005
• University of Göttingen, GK-Kolloquium, January 2005
• Luminy, Seminar, November 2004
• University of Marseille, Seminar, November 2004
• ENS Lyon, ENS-Seminar, November 2004
• University of Grenoble, Tripod Seminaire, November 2004
• MFO Oberwolfach, Topology workshop, September 2004
• Bonn, NRW Topology meeting, April 2004
• Diablerets, Invariants sous Quasi-Isometrie, April 2004
• University of Augsburg, Differentialgeometrie-Seminar, November 2003
• ETH Zürich, Seminar, June 2003
• University of Basel, Seminar, November 2001