Dr. Holger Kammeyer
 Office Hours: nach Vereinbarung
 Room: 1.007
 Phone: +49 721 60843707
 Fax: +49 721 60842148
 holger kammeyer ∂kit edu
Karlsruher Institut für Technologie
MATH  IAG  AG Topologie
Englerstr. 2  Mathebau (20.30)
76131 Karlsruhe
I am a postdoc in the topology group of the Institute for Algebra and Geometry at KIT. My mathematical interests range around algebraic topology, ℓ²invariants and arithmetic groups. I am member of the Priority Program 2026 "Geometry at Infinity" and of the RTG 2229 "Asymptotic Invariants and Limits of Groups and Spaces". Here you can find slides of a talk on "The construction of the regular 65.537gon with compass and straightedge" at the Day of Mathematics 2019 (in German).
Publications
An uptodate and userfriendly introduction to the rapidly developing field of ℓ²invariants.
Title  Coauthors  Year 

Adelic superrigidity and profinitely solitary lattices  Steffen Kionke 
2020 
On the profinite rigidity of lattices in higher rank Lie groups  Steffen Kionke 
2020 
Products of free groups in Lie groups  Caterina Campagnolo 
2020 
Title  Coauthors  Journal 

Profinite commensurability of Sarithmetic groups   
to appear in Acta Arithmetica 
Profinite invariants of arithmetic groups  Steffen Kionke, Jean Raimbault, Roman Sauer 
Forum of Mathematics, Sigma, 
Sarithmetic spinor groups with the same finite quotients and distinct L²cohomology  Roman Sauer 
Groups, Geometry, and Dynamics, 
Introduction to ℓ²invariants   
Springer Lecture Notes in Mathematics, 
The shrinkage type of knots   
Bull. Lond. Math. Soc., 493 (2017), 428–442 
Approximating NovikovShubin numbers of virtually cyclic coverings   
Groups, Geometry, and Dynamics, 114 (2017), 1231–1251 
The FarrellJones conjecture for arbitrary lattices in virtually connected Lie groups  Wolfgang Lück, Henrik Rüping 
Geometry & Topology,
203 (2016), 12751287 
L²invariants of nonuniform lattices in semisimple Lie groups   
Algebraic & Geometric Topology, 14 (2014), 24752509 
An explicit rational structure for real semisimple Lie algebras   
Journal of Lie Theory, 24, No. 2 (2014), 307319 
Title  Coauthors  Journal 

From Betti numbers to L²Betti numbers  Roman Sauer 
to appear in Oberwolfach Snapshots of Modern Mathematics 
The HestonHullWhite Model I: Finance and Analytics  Jörg Kienitz 
Wilmott Magazine, Issues 57, 58, 59, (Jan 2012, March 2012, May 2012), 4653, 3445, 4449 
Title  Type, University 

L²invariants of nonuniform lattices in semisimple Lie groups  doctoral thesis, University of Göttingen 
On Exotic Manifolds  diploma thesis, University of Göttingen 
Talks
 International young seminar on bounded cohomology and simplicial volume
Talk: "L2Betti numbers and L2Torsion"
December 2020, Lyon/Regensburg  RTGColloquium
Talk: "Profinite properties of lattices in Lie groups"
February 2020, Göttingen  SFB Vorlesung
Talk: "Profinite invariants of arithmetic groups"
November 2018, Regensburg  Growth in Topology and Number Theory: Volume, Entropy, and L2torsion
Talk: "Profiniteness questions for L2Betti numbers of Sarithmetic groups"
July 2018, Bonn  L2invariants and their analogues in positive characteristic
Talk: "Profiniteness questions for L2Betti numbers of Sarithmetic groups"
June 2018, Madrid, Spain  Joint annual convention GDMV 2018
Talk: "Profinite commensurability of Sarithmetic groups"
March 2018, Paderborn  Nacht der Wissenschaft (Night of Science)
Talk: "Die Konstruktion des regelmäßigen 65.537Ecks mit Zirkel und Lineal"
November 2017, Karlsruhe  Manifolds and groups
Talk: "Cyclic knot coverings and transcendental numbers"
September 2017, Regensburg  Summer school on "Growth in geometry and topology"
Mini course: "Intro to L2Betti numbers / L2torsion and torsion growth in homology"
August 2017, Les Diablerets, Switzerland  Oberseminar Topologie
Talk: "Secondary L2invariants of groups and knots"
May 2017, Münster  Oberseminar Topologie
Talk:"L²invariants of groups and knots"
September 2016, Bonn  Oberseminar Global Anlaysis
Talk: "Approximating NovikovShubin numbers along finite coverings"
January 2016, Regensburg  Geometry day
Talk: "The FarrellJones conjecture and lattices in Lie groups"
October 2015, Heidelberg  Topology Retreat
Talk: "Introduction to L²torsion"
September 2015, Bedlewo, Poland  Oberseminar Topologie
 Talk: "L²invariants and approximation along finite coverings"
June 2015, Münster  AGSeminar Topologie
 Talk: "Local rigidity and the FarrellJones conjecture"
February 2015, Karlsruhe  Workshop "Topologie"
 Short talk: "The FarrellJones conjecture for lattices in Lie groups"
September 2014, Oberwolfach  Oberseminar Differentialgeometrie
Talk: "Local rigidity and the FarrellJones conjecture"
June 2014, Augsburg  Seminario de Topología Algebraica
Talk: "Rigidez local y la conjetura de FarrellJones"
May 2014, Morelia, Mexico  Arbeitsgemeinschaft "Superrigidity"
Talk: "Factor theorems for lattices in products of groups (BaderShalom)"
March/April 2014, Oberwolfach  GKKolloquium Regensburg
Talk: "L²invariants and groups"
October 2013, Regensburg  Oberseminar Regensburg
Talk: "NovikovShubin numbers of arithmetic groups"
October 2013, Regensburg  Oberseminar Topologie
Talk: "L²invariants of nonuniform lattices in semisimple Lie groups"
October 2013, Bonn  Operator Algebra Seminar
Talk: "On L²invariants of lattices in semisimple Lie groups"
January 2013, Copenhagen, Denmark
Conferences
Title  Venue  In  Coorganized with 

Conference: Arithmetic Groups and 3manifolds  Hagen 
Steffen Kionke, Haluk Sengun 

Workshop: New directions in L2Invariants  Bonn 
Aditi Kar, Steffen Kionke, Jean Raimbault 
Teaching
 Lecture "Algebraic Topology II" online, recorded, YouTube channel
 RG Seminar "Topology" Thu 04:0005:30 pm, SR 2.058
 Lecture "Algebraic Topology" Thu 02:0003:30 pm, 1.012 UG, Fr 09:4511:15 am, 1.025 UG
 Seminar "Representation theory of finite groups" block seminar
 RG Seminar "Topology" Thu 03:4505:15 pm, SR 2.059 (20.30)
 Exercise class for Linear Algebra II Fr 02:00  03:30 pm, FritzHallerHörsaal
 RGSeminar "Topology" Fr 09:4511:15 am, Raum 2.059 (20.30)
 Exercise class for Linear Algebra and Analytic Geometry I Mon 03:45  05:15 pm, CarlBenzHörsaal
 RGSeminar "Topology" Thu 03:4505:15 pm, 2.058 (20.30)
 Workshop on current developments around the Atiyah conjecture 19.11.18  21.11.18
 Seminar "Projective Geometry" block course 07/23  07/25/2018, SR 0.016 (20.30) seminar announcement
 RGSeminar "Topology" Thu 03:4505:15 pm, 2.059 (20.30)
 Lecture "Mathematics for Natural Sciences" Tue 08:0009:30 am, Fr 08:4509:30 am, 30.46 Chemie Neuer Hörsaal
 RGSeminar "Topology" Thu 03:4505:15 pm, 2.058 (20.30)
 Seminar: "Differential topology" Thu 09:4511:15 am, 1.009(UG) (20.30) seminar announcement
 Proseminar: "Proofs from THE BOOK" Thu 02:0003:30 pm, 2.059 (20.30) proseminar announcement
 RGSeminar "Arithmetic hyperbolic 3manifolds" Thu 03:4505:15 pm 2.059 (20.30) seminar announcement
 Lecture "Algebraic Topology" Tue 11:30 am01:00 pm, 2.058 (20.30), Thu 11:30 am01:00 pm, 0.014 (20.30)
 Tutorial "Algebraic Topology" Wed 05:3007:00 pm, 2.059 (20.30)
tutor: Jakob Albers  RGSeminar "Topology" Thu 02:0003:30pm, 2.058 (20.30)
 Lecture "L²invariants" Thu 03:4505:15 pm, room 2.058 (20.30)
 Problem class "L²invariants" Mon 02:0003:30 pm, room 2.059 (20.30)
Teaching assistant: Sabine Braun; Starts 10/26/2015  RG Seminar "Topology" Thu 05:3007:00 pm, room 2.058 (20.30)
More information on the lecture "L²invariants" is given in the course announcement.
 Exercise class: "Algebraic Topology" Fri 11:3001:00 pm, room 2.059 (20.30)
 Seminar: "Projektive Geometrie" Thu 05:3007:00 pm, room 3.060 (20.30)
 RG Seminar: "Topology" Thu 02:0003:30 pm, room 2.058 (20.30)
Supervision
Title  Type  Student 

The Lefschetz fixed point theorem: from simplicial to CW complexes  Masterarbeit  Gotami Heller 
Homologies and elations in the projective and Euclidean plane  Bachelorarbeit  Cédric Dujardin 
L2Betti numbers and profinite completions of groups  Master thesis  Nico Stucki 
Construction of Thom spectra for bordism with Gstructure  Bachelor thesis  Amelie Flatt 
Short CV
Since April 2015  Postdoc at Institute for Algebra and Geometry (working with Roman Sauer) 
Karlsruhe Institute of Technology 
July 2013  March 2015  Postdoc at Mathematical Institute (working with Wolfgang Lück) 
University of Bonn 
July 2010  May 2013  Doctoral studies at Mathematical Institute (working with Thomas Schick) 
University of Göttingen 
August 2009  June 2010  Fulbright scholar at Department of Mathematics  University of California Berkeley 
July 2008  October 2008  Internship in team "Quantitative Analysis"  Deutsche Postbank, Bonn 
October 2004  July 2009  Diploma studies in mathematics with minor theoretical physics  University of Göttingen 