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 |

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 algebraic topology, ℓ²-invariants, profinite and arithmetic groups. I am PI within the Priority Program 2026 "Geometry at Infinity" and member of the RTG 2240 "Algebro-Geometric Methods in Algebra, Arithmetic and Topology".

Title | Coauthors | Year |

On the profinite rigidity of lattices in higher rank Lie groups | S. Kionke | 2020 |

Title | Coauthors | Journal |

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 |

From Betti numbers to ℓ²-Betti numbers | R. Sauer | Snapshots of modern mathematics from Oberwolfach, (2020.01), 1-11 |

Introduction to ℓ²-invariants | Springer Lecture Notes in Mathematics, Vol. 2247 (2019), viii+181 pp | |

The shrinkage type of knots | Bull. Lond. Math. Soc., 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 |

Title | Type | University |

ℓ²-invariants of nonuniform lattices in semisimple Lie groups | doctoral thesis | University of Göttingen |

On exotic manifolds | diploma thesis | University of Göttingen |

- Topology Retreat II

Talk:*"On and around profinite rigidity"*

Ocotober 2021, Bedlewo, Poland - Invariants and Structures in Low-Dimensional Topology

Talk:*"On and around profinite rigidity"*

September 2021, Oberwolfach - Seminar Algebra-Geometry-Combinatorics

Talk:*"On the profinite rigidity of higher rank lattices"*

June 2021, Dresden - Ring lecture RTG 2240

Talk:*"On arithmetic groups with the same finite quotients"*

June 2021, Düsseldorf - PhD and guest seminar

Talk:*"ℓ²-invariants, profinite rigidity, and arithmetic groups"*

May 2021, Wuppertal - Oberseminar "Groups and Geometry"

Talk:*"On the profinite rigidity of higher rank lattices"*

May 2021, Bielefeld - International young seminar on bounded cohomology and simplicial volume

Talk:*"Introduction to ℓ²-Betti numbers"*

December 2020, Lyon/Regensburg - RTG-Colloquium

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 ℓ²-torsion

Talk:*"Profiniteness questions for ℓ²-Betti numbers of S-arithmetic groups"*

July 2018, Bonn - ℓ²-invariants and their analogues in positive characteristic

Talk:*"Profiniteness questions for ℓ²-Betti numbers of S-arithmetic groups"*

June 2018, Madrid, Spain - Joint annual convention GDMV 2018

Talk:*"Profinite commensurability of S-arithmetic groups"*

March 2018, Paderborn - Nacht der Wissenschaft (Night of Science)

Talk:*"Die Konstruktion des regelmäßigen 65.537-Ecks mit Zirkel und Lineal"*

November 2017, Karlsruhe, slides - 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 ℓ²-Betti numbers / ℓ²-torsion and torsion growth in homology"*

August 2017, Les Diablerets, Switzerland - Oberseminar Topologie

Talk:*"Secondary ℓ²-invariants of groups and knots"*

May 2017, Münster - Oberseminar Topologie

Talk:*"ℓ²-invariants of groups and knots"*

September 2016, Bonn - Oberseminar Global Anlaysis

Talk:*"Approximating Novikov-Shubin numbers along finite coverings"*

January 2016, Regensburg - Geometry day

Talk:*"The Farrell-Jones conjecture and lattices in Lie groups"*

October 2015, Heidelberg - Topology Retreat

Talk:*"Introduction to ℓ²-torsion"*

September 2015, Bedlewo, Poland - Oberseminar Topologie

Talk:*"ℓ²-invariants and approximation along finite coverings"*

June 2015, Münster - AG-Seminar Topologie

Talk:*"Local rigidity and the Farrell-Jones conjecture"*

February 2015, Karlsruhe - Workshop "Topologie"

Short talk:*"The Farrell-Jones conjecture for lattices in Lie groups"*

September 2014, Oberwolfach - Oberseminar Differentialgeometrie

Talk:*"Local rigidity and the Farrell-Jones conjecture"*

June 2014, Augsburg - Seminario de Topología Algebraica

Talk:*"Rigidez local y la conjetura de Farrell-Jones"*

May 2014, Morelia, Mexico - Arbeitsgemeinschaft "Superrigidity"

Talk:*"Factor theorems for lattices in products of groups (Bader-Shalom)"*

March/April 2014, Oberwolfach - GK-Kolloquium Regensburg

Talk:*"ℓ²-invariants and groups"*

October 2013, Regensburg - Oberseminar Regensburg

Talk:*"Novikov-Shubin numbers of arithmetic groups"*

October 2013, Regensburg - Oberseminar Topologie

Talk:*"ℓ²-invariants of nonuniform lattices in semisimple Lie groups"*

October 2013, Bonn - Operator Algebra Seminar

Talk:*"On ℓ²-invariants of lattices in semisimple Lie groups"*

January 2013, Copenhagen, Denmark

Title | Venue | Coorganized with |

Conference: Arithmetic Groups and 3-manifolds | University of Hagen | S. Kionke, H. Sengun |

Workshop: Current developments around the Atiyah conjecture | Karlsruhe Institute of Technology | B. Waßermann |

Workshop: New directions in ℓ²-invariants | HIM Bonn | A. Kar, S. Kionke, J. Raimbault |

- Proseminar "Miniatures of linear algebra"
- Seminar on algebraic topology
- Lecture "Algebraic Topology II" see YouTube channel
- Lecture "Algebraic Topology" see YouTube channel
- Seminar "Representation theory of finite groups"
- Exercise class for Linear Algebra II
- Exercise class for Linear Algebra and Analytic Geometry I
- Seminar "Projective Geometry"
- Lecture "Mathematics for Natural Sciences"
- Seminar: "Differential topology"
- Proseminar: "Proofs from THE BOOK"
- RG-Seminar "Arithmetic hyperbolic 3-manifolds"
- Lecture "Algebraic Topology"
- Lecture "ℓ²-invariants"
- Exercise class: "Algebraic Topology"
- Seminar: "Projektive Geometrie"

Title | Type | Student |

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 |

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 |

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 |