HHU Mathematics Algebra and number theory Holger Kammeyer
Holger Kammeyer (photo by Tanja Meissner) 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, ℓ²-invariants, and algebraic topology. I am PI within the Priority Program 2026 "Geometry at Infinity" and the RTG 2240 "Algebro-Geometric Methods in Algebra, Arithmetic and Topology".




On the Euler characteristic of S-arithmetic groups G. Serafini 2024
Gassmann triples with special cycle types and applications S. Kionke 2023


Galois cohomology and profinitely solitary Chevalley groups R. Spitler Mathematische Annalen, (2024)
Bounded cohomology is not a profinite invariant D. Echtler Canadian Mathematical Bulletin, 67-2 (2024), 379-390
On absolutely profinitely solitary lattices in higher rank Lie groups Proceedings of the American Mathematical Society, 151 (2023), 1801-1809
On the profinite rigidity of lattices in higher rank Lie groups S. Kionke Mathematical Proceedings of the Cambridge Philosophical Society, 174-2 (2023), 369-384
ℓ²-Betti numbers In "Bounded Cohomology and Simplicial Volume", LMS Lecture Notes Series 479 (2023), 57-62
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, 313-1 (2021), 137-158
Products of free groups in Lie groups C. Campagnolo Journal of Algebra, Volume 579, (2021), 237-255
Profinite commensurability of S-arithmetic groups Acta Arithmetica, 197.3 (2021), 311-330
Profinite invariants of arithmetic groups S. Kionke, J. Raimbault, R. Sauer Forum of Mathematics, Sigma, Vol. 8, (2020), 1-22
S-arithmetic spinor groups with the same finite quotients and distinct ℓ²-cohomology R. Sauer Groups, Geometry, and Dynamics, 14 (2020), no. 3, 857-869
Introduction to ℓ²-invariants Springer Lecture Notes in Mathematics, Vol. 2247 (2019), viii+181 pp
The shrinkage type of knots Bulletin of the London Mathematical Society, 49-3 (2017), 428-442
Approximating Novikov-Shubin numbers of virtually cyclic coverings Groups, Geometry, and Dynamics, 11-4 (2017), 1231-1251
The Farrell-Jones conjecture for arbitrary lattices in virtually connected Lie groups W. Lück, H. Rüping Geometry & Topology, 20-3 (2016), 1275-1287
ℓ²-invariants of nonuniform lattices in semisimple Lie groups Algebraic & Geometric Topology, 14 (2014), 2475-2509
An explicit rational structure for real semisimple Lie algebras Journal of Lie Theory, 24, No. 2 (2014), 307-319
The Heston-Hull-White Model III: Design and Implementation J. Kienitz Wilmott Magazine, Issues 59, (May 2012), 44-49
The Heston-Hull-White Model II: Numerics and Examples J. Kienitz Wilmott Magazine, Issues 58, (March 2012), 34-45
The Heston-Hull-White Model I: Finance and Analytics J. Kienitz Wilmott Magazine, Issues 57, (Jan 2012), 46-53


ℓ²-invariants of nonuniform lattices in semisimple Lie groups doctoral thesis University of Göttingen
On exotic manifolds diploma thesis University of Göttingen

Talks and Travel




TitleYearVenueCoorganized 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 3-manifolds 2022 MPIM Bonn S. Kionke, A. Reid, H. Sengun
Conference: Arithmetic Groups and 3-manifolds 2020 University of Hagen S. Kionke, H. Sengun
Workshop: Current developments around the Atiyah conjecture 2018 KIT Karlsruhe B. Waßermann
Workshop: New directions in ℓ²-invariants 2016 HIM Bonn A. Kar, S. Kionke, J. Raimbault


Winter term 2024/25

Summer term 2024

Winter term 2023/24

Summer term 2023

Winter term 2022/23

Summer term 2022

Winter term 2021/22

Lecture notes/articles for students

Einführung in die Topologie (Introduction to topology), 94 MB2022
Topologie 1 (Topology 1), 90 MB2023
Topologie 2 (Topology 2), 83 MB2023
ℓ²-Invarianten (ℓ²-invariants), 49 MB2024
From Betti numbers to ℓ²-Betti numbers (with R. Sauer)
Snapshots of modern mathematics from Oberwolfach, (2020.01), 1-11

Previous courses taught at Karlsruhe Intitute of Technology:


PhD students:

Picture with PhD students

MSc and BSc students:

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 Δ-Complexes 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
ℓ²-Betti numbers and profinite completions of groups Master thesis Nico Stucki
Construction of Thom spectra for bordism with G-structure Bachelor thesis Amelie Flatt

Short CV

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