Jun.Prof. Dr. Holger Kammeyer Mathematical Institute Heinrich Heine University Düsseldorf Universitätsstraße 1 40225 Düsseldorf, Germany building: 25.22, office: 03.48 phone: +49 211 81 14490 email: holger.kammeyer@hhu.de administration: Sabine May 
I am assistant professor for "algebra and geometry" at the Mathematical Institute of Heinrich Heine University Düsseldorf in the algebra and number theory group. My research interests range around profinite and arithmetic groups, ℓ²invariants, and algebraic topology. I am PI within the Priority Program 2026 "Geometry at Infinity" and the RTG 2240 "AlgebroGeometric Methods in Algebra, Arithmetic and Topology". For inquiries from the nearby schools, please refer to Angebote für Schüler*innen (in German) and feel free to contact me for any questions.

Title  Coauthors  Year 
On the Euler characteristic of Sarithmetic groups  G. Serafini  2024 
Gassmann triples with special cycle types and applications  S. Kionke  (to appear in Proc. Edinb. Math. Soc.) 
Title  Coauthors  Journal/Series 
Galois cohomology and profinitely solitary Chevalley groups  R. Spitler  Mathematische Annalen, 390 (2024), no. 2, 24972511 
Bounded cohomology is not a profinite invariant  D. Echtler  Canadian Mathematical Bulletin, 672 (2024), 379390 
On absolutely profinitely solitary lattices in higher rank Lie groups  Proceedings of the American Mathematical Society, 151 (2023), 18011809  
On the profinite rigidity of lattices in higher rank Lie groups  S. Kionke  Mathematical Proceedings of the Cambridge Philosophical Society, 1742 (2023), 369384 
ℓ²Betti numbers  In "Bounded Cohomology and Simplicial Volume", LMS Lecture Notes Series 479 (2023), 5762  
Introduction to Algebraic Topology  Birkhäuser Compact Textbooks in Mathematics (2022), xi, 172 pp  
Adelic superrigidity and profinitely solitary lattices  S. Kionke  Pacific Journal of Mathematics, 3131 (2021), 137158 
Products of free groups in Lie groups  C. Campagnolo  Journal of Algebra, Volume 579, (2021), 237255 
Profinite commensurability of Sarithmetic groups  Acta Arithmetica, 197.3 (2021), 311330  
Profinite invariants of arithmetic groups  S. Kionke, J. Raimbault, R. Sauer  Forum of Mathematics, Sigma, Vol. 8, (2020), 122 
Sarithmetic spinor groups with the same finite quotients and distinct ℓ²cohomology  R. Sauer  Groups, Geometry, and Dynamics, 14 (2020), no. 3, 857869 
Introduction to ℓ²invariants  Springer Lecture Notes in Mathematics, Vol. 2247 (2019), viii+181 pp  
The shrinkage type of knots  Bulletin of the London Mathematical Society, 493 (2017), 428442  
Approximating NovikovShubin numbers of virtually cyclic coverings  Groups, Geometry, and Dynamics, 114 (2017), 12311251  
The FarrellJones conjecture for arbitrary lattices in virtually connected Lie groups  W. Lück, H. 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  
The HestonHullWhite Model III: Design and Implementation  J. Kienitz  Wilmott Magazine, Issues 59, (May 2012), 4449 
The HestonHullWhite Model II: Numerics and Examples  J. Kienitz  Wilmott Magazine, Issues 58, (March 2012), 3445 
The HestonHullWhite Model I: Finance and Analytics  J. Kienitz  Wilmott Magazine, Issues 57, (Jan 2012), 4653 
Title  Type  University 
ℓ²invariants of nonuniform lattices in semisimple Lie groups  doctoral thesis  University of Göttingen 
On exotic manifolds  diploma thesis  University of Göttingen 
Title  Year 
Halbeinfache LieAlgebren (Semisimple Lie algebras), 66 MB  2024 
ℓ²Invarianten (ℓ²invariants), 49 MB  2024 
Einführung in die Topologie (Introduction to topology), 94 MB  2022 
Topologie 1 (Topology 1), 90 MB  2023 
Topologie 2 (Topology 2), 83 MB  2023 
From Betti numbers to ℓ²Betti numbers (with R. Sauer) Snapshots of modern mathematics from Oberwolfach, (2020.01), 111  2020 
Slides: Faire und unfaire Preise für Finanzderivate  2024 
Slides: Die Konstruktion des regelmäßigen 65.537Ecks mit Zirkel und Lineal  2019 
Title  Year  Venue  Coorganized with 
RTG summer school: "Analytic and arithmetic groups"  2024  HHU Düsseldorf  B. Klopsch 
Felix Klein Colloquium  2024  HHU Düsseldorf  I. Halupczok, B. Klopsch 
Conference: Arithmetic Groups and 3manifolds  2022  MPIM Bonn  S. Kionke, A. Reid, H. Sengun 
Conference: Arithmetic Groups and 3manifolds  2020  University of Hagen  S. Kionke, H. Sengun 
Workshop: Current developments around the Atiyah conjecture  2018  KIT Karlsruhe  B. Waßermann 
Workshop: New directions in ℓ²invariants  2016  HIM Bonn  A. Kar, S. Kionke, J. Raimbault 
Title  Type  Student 
Satake and Vogan diagrams of real simple Lie algebras  Bachelor thesis  Marek Kasper 
Model structures on different categories  Bachelor thesis  Daniel Dratschuk 
Implementation of an Algorithm to Compute the Integral Homology of ΔComplexes  Bachelor thesis  Mohamed Winkelmann 
The Lefschetz fixed point theorem: from simplicial to CW complexes  Master thesis  Gotami Heller 
Homologies and elations in the projective and Euclidean plane  Bachelor thesis  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 
Since August 2021  "Juniorprofessor" (assistant professor) for "algebra and geometry" at Mathematical Institute  Heinrich Heine University Düsseldorf 
November 2017  July 2021  "Akademischer Rat auf Zeit" (lecturer) at Institute for Algebra and Geometry 
Karlsruhe Institute of Technology 
April 2015  October 2017  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 
October 2004  July 2009  Diploma studies in mathematics with minor theoretical physics  University of Göttingen 