Prof. Dr. Franziska Jahnke

Mathematical Institute and
Institute for Mathematical Logic and Foundational Research
Department of Mathematics and Computer Science
University of Münster
Einsteinstraße 62
48149 Münster (Germany)

Room: 801
Tel.: +49 251 83 32 764
e-mail: franziska.jahnke AT uni-muenster.de

Research Interests

Arithmetic and Model theory of fields, in particular perfectoid fields and finitely ramified henselian valued fields, arithmetic definability of valuations and connections to infinite combinatorics.

News

• Upcoming Workshop Model theoretic methods in non-archimedean geometry, Münster, 25.-31.01.2025. Co-Organization with Piotr Achinger and Michal Szachniewicz
• From September 2024 on, I am once again a professor in Münster, after a year at the Institute for Logic, Language and Computation, University of Amsterdam
• Lecture notes from my mini course at the Summer School on Motivic Integration, 12.-16.9.2022, HHU Düsseldorf
• Teaching prize 2022 (Department of Mathematics and Computer Science)
• Member of the Jungen Kollegs of the North Rhine Westfalian Academy of Sciences, Humainities and the Arts, press release of the WWU (in German), my 5-minute-talk (in German)
• Fellow of the Daimler und Benz Stiftung
• Investigator in the Cluster of Excellence Mathematics Münster: Dynamics - Geometry - Structure, my portrait on the MM web page
• Deputy Equal Opportunity Representative of the Department of Mathematics and Computer Science

Talks and Events (selection)

• Co-organizor of the conference Young Women in Model Theory (Bonn, 11.03.-14.03.2024)
• Co-organizor of the conference Model theory and groups (Münster, 25.09.-29.09.2023)
• Co-organizer of the conference Model theory of valued fields (CIRM, Luminy, 29.05.-02.06.2023)
• Invited speaker at the Joint Mathematics Meeting (ASL invited address), Boston, 2023.
• Talk Dividing lines in the model theory of fields Betty B. Seminar, November 2021, Paris
• Talk Decidability and definability in unramified henselian valued fields, Workshop on Trends in Pure and Applied Model Theory, Fields Institute, Toronto, 27.07.21
• Research Member at the MSRI Programm Decidability, Definability and Computability in Number Theory, August - December 2020 (my 5 minute talk)
  • Organizer of the MSRI Reading Seminar Valuations on dp-finite fields, my slides for the introductory talk, the Christmas review and the finale overview
  • Co-Organizer of the MSRI Seminar Valuation Theory jointly with Sylvy Anscombe and Philip Dittmann
• Co-organizer of the Conference Model theory of valued fields and applications (Münster, 10.06.-14.06.2019)

Teaching

• Lecture course Introduction to Algebra (SS 2025)
• Seminar Introduction to Stability Theory
• Condensed seminar on model theory and algebraic geometry Model Theory meets Algebraic Geometry, Landhaus Rothenberge
• Lecture course Introduction to Algebra (SS 2023)
• Research seminar Model Theory
• Seminar on algebra and model theory: Galois-characterization of the p-adic numbers (WS 22/23), Poster
• Lecture course Logical Foundations (WS 22/23)
• Condensed seminar on model theory Model Theory of Fields (SS 2022), Landhaus Rothenberge
• Teacher student seminar The p-adic numbers (SS 2022)
• Lecture course Logic for teacher students (SS 2021)
• MSRI Reading Seminar Valuations on dp-finite fields, here are my slides for the introduction, der Christmas review and the finale
• MSRI Seminar Valuation Theory coorganized with Sylvy Anscombe and Philip Dittmann
• Logical Foundations (WS 2019/20)
• Logic (SS 2019)
• Seminar Continuous Logic (SS 2019)
• Model Theory (WS 2018/19)
• Seminar Simple Theories (WS 2018/19)
• Logic (SS 2018)
• Valued Fields (WS 2017/18)
• Seminar Stable and NIP Fields (SS 2017)
• Model Theory Month in Münster (18.04.-20.05.16), see here for the (preliminary) notes of my course on Valued Fields
• Profinite and pseudofinite groups (SS 2016)
• Seminar Topics in pseudofinite Model Theory (SS 2016)
• Theory of Computation (WS 2015/16)
• Seminar Algebra and model theory: the p-adic numbers (WS 2015/16)
• Seminar Dynamics of Polish groups and Model Theory (WS 2015/16)
• Stable Groups (SS 2015)
• Seminar Introduction to the theory of buildings (SS 2015)
• Model Theory (WS 2014/15)
• Higher Algebra 1 (SS 2014)
• Computation Theory (WS 2013/14)
• Group Theory (SS 2013)
• Foundations of Logic (SS 2013)

Papers and Preprints

• Franziska Jahnke: Henselian Valuations and Absolute Galois Groups. DPhil Thesis, 2013, Oxford University.
  Supervised by Dr Jochen Koenigsmann.
• Franziska Jahnke and Jochen Koenigsmann: Definable henselian valuations. The Journal of Symbolic Logic / Volume 80 / Issue 01 / March 2015, pp 85-99.
• Arno Fehm and Franziska Jahnke: On almost small absolute Galois groups. Israel Journal of Mathematics, July 2016, Volume 214, Issue 1, pp. 193-207.
• Franziska Jahnke and Jochen Koenigsmann: Uniformly defining p-henselian valuations. Annals of Pure and Applied Logic 166 (2015), pp. 741-754.
• Franziska Jahnke: Uniformly defining p-henselian valuations (joint work with Jochen Koenigsmann). Extended abstract, Oberwolfach Report (4) 2014, pp. 2788-2789.
• Arno Fehm and Franziska Jahnke: On the quantifier complexity of definable canonical henselian valuations. Mathematical Logic Quarterly 61 (4-5/2015), pp. 347-361.
• Franziska Jahnke and Jochen Koenigsmann: Defining coarsenings of valuations. Proceedings of the Edinburgh Mathematical Society, August 2017, Volume 60, Issue 3, pp. 665-687.
• Immanuel Halupczok and Franziska Jahnke: A definable henselian valuation with high quantifier complexity. Mathematical Logic Quarterly 61 (4-5/2015), pp. 362-366.
• Franziska Jahnke, Pierre Simon and Erik Walsberg: Dp-minimal valued fields. The Journal of Symbolic Logic / Volume 82 / Issue 01 / March 2017, pp. 151-165.
• Sylvy Anscombe and Franziska Jahnke: Henselianity in the language of rings. Annals of Pure and Applied Logic 169 (2018), pp. 872-895.
• Franziska Jahnke: When does dependence transfer from fields to henselian expansions? Extended abstract, Oberwolfach Report (1) 2016, pp. 29-32.
• Franziska Jahnke and Pierre Simon: NIP henselian valued fields. Archive of Mathematical Logic, 59(1), 167-178 (2020).
• Franziska Jahnke: When does NIP transfer from fields to henselian expansions? To appear in Journal of Mathematical Logic.
• Arno Fehm and Franziska Jahnke: Recent Progress on Definability of Henselian Valuations. Survey article. F. Broglia, F. Delon, M. Dickmann, D. Gondard, and V. Powers (eds.), Ordered Algebraic Structures and Related Topics, Contemporary Mathematics 697, 2017, pp. 135-143.
• Yatir Halevi, Assaf Hasson and Franziska Jahnke: A conjectural classification of strongly dependent fields. Bulletin of Symbolic Logic 25 (2019), pp. 182-195.
• Yatir Halevi, Assaf Hasson and Franziska Jahnke: Definable V-topologies, Henselianity and NIP. Journal of Mathematical Logic (2020), no. 2, 2050008, 33 pp.
• Sylvy Anscombe and Franziska Jahnke: The Model Theory of Cohen rings. Confluentes Mathematici, 14.2 (2022), pp. 1–28.
• Sylvy Anscombe and Franziska Jahnke: Characterizing NIP henselian fields. Journal of the London Mathematical Society, Volume 109 , Issue 3, March 2024, e12868.
• Philip Dittmann, Franziska Jahnke, Sebastian Krapp and Salma Kuhlmann: Definable valuations on ordered fields. Model Theory, Vol. 2 (2023), No. 1, pp. 101-120.
• Franziska Jahnke and Konstantinos Kartas: Beyond the Fontaine-Wintenberger Theorem, to appear in Journal of the AMS.
• Sylvy Anscombe, Philip Dittmann and Franziska Jahnke: Ax-Kochen-Ershov principles for finitely ramified henselian fields. Transactions of the American Mathematical Society, 377-12:8963–8988, 2024.
• Blaise Boissonneau, Anna De Mase, Franziska Jahnke und Pierre Touchard: Growing Spines ad Infinitum. Preprint, 2025.

Textbook

• Franziska Jahnke: An introduction to valued fields, book chapter in Lectures in Model Theory (see next item), pp. 119 - 149.
• Franziska Jahnke, Daniel Palacin, Katrin Tent (editors): Lectures in Model Theory. Published in the series Münster Lectures in Mathematics of the European Mathematical Society, 222 pages, ISBN 978-3-03719-184-2, April 2018.

Notes (not intended for publication)

• Franziska Jahnke and Jochen Koenigsmann: A p-adic example for the characterization of the canonical p-henselian valuation. Manuscript, 2014.

Supervision

Postdocs

• Since January 2025: Dr. Mariana Vicaria, scholarship in the postdoc programme of the Humboldt Foundation
• Since September 2024: Dr. Floris Vermeulen, scholarship in the postdoc programme of the Humboldt Foundation

PhD theses

• Since November 2022: Margarete Ketelsen (PhD student), Ada-Lovelace-Fellow
• Since November 2021: Simone Ramello (PhD student), co-supervision with Prof. Dr. Martin Hils, financed by the DFG project Model theory of valued fields with endomorphism. Submitted 2024.
• Blaise Boissonneau: Combinatorial Complexity in Henselian Valued Fields. PhD thesis, defended in June 2022. Now assistent in Düsseldorf.

Bachelor and Master theses

• Lukas Pieper: Compressibility in Model Theory. MSc thesis, University of Amsterdam, 2024. Now PhD student at the Charles-University Prague.
• Niclas Oberhoff: SAT and Variants Bachelor thesis, 2023.
• Arman Ahmadi: Der Satz von Arrow im endlichen und unendlichen Fall. Bachelor thesis, 2023.
• Paul Edelbrock: Infinite superstable fields are algebraically closed Bachelor thesis, 2023.
• Antonia Bruns: Ringtheorie und Primfaktorzerlegung. Bachelor thesis (in German), 2023.
• Ines Brauer: On axioms for propositional logic. Bachelor thesis (in German), 2023.
• Luca Bast: Definability of the p-adic valuation in extensions of Qp. Bachelor thesis (in German), 2023.
• Anna Sielenkämper: (Un)Decicability in the natural numbers. Master thesis (Master of Education), 2022.
• Karen Toben (TU Dortmund): Classification with p-adic neural networks: Applications to time series segmentations in traffic. Master thesis (in German, computer science), 2021, co-supervision with JProf. Dr. Thomas Liebig.
• Mirco Frerichs: Fraisse-Limiten und die logische Betrachten des 0-1-Gesetzes auf Zufallsgraphen. Bachelor thesis (in German).
• Simone Ramello (University of Turin): Etale methods in the model theory of fields. Master thesis, 2021, co-supervision with Prof. Dr. Martin Hils
• Florian Felix: A new approach to Ershov's wonderful fields. Master thesis, 2021. Afterwards PhD student at the HHU Düsseldorf.
• Fan Feng: Tree properties in model theory. Master thesis, 2020. Afterwards PhD student at Leipzig University.
• Thomas Koch: NIP Körper und Henselität in positiver Charakteristik. Bachelor thesis (in German), 2020.
• Leon Pernak: Computable and elementary functions. Bachelor thesis (in computer science), 2018.
• Florian Severin: Varianten von Hensels Lemma. Master thesis (in German), 2016. Now PhD student at the HHU Düsseldorf.
• Maurice Krause: Komplexitätsklassen und Hierarchiesätze. Bachelor thesis (in German), 2016. Now PhD student at the WWU Münster
• Justin Dreyer: Hilbert's 10. Problem: Diophantine sets are not decidable. Bachelor thesis (in German), 2016.

Outreach

• Talk "p-adic Numbers" Open Day 07.11.19 (in German)
• Article in DMV Mitteilungen 4/2018 (Publication of the German Mathematical Society), see also the cover page here
• Interview in the newspaper "Rheinische Post" (in German, appeared 15.11.19)
• Interview with wissensschule.de (in German)
• Article on the university homepage about my research

Academic CV

• 2004 - 2009: Undergraduate student (Diplom) at the Albert-Ludwigs-Universität Freiburg
• 2009 - 2013: DPhil student at Oxford University
• 2013 - 2017: Research assistant at the WWU Münster
• 2017 - 2024: Junior professor at the WWU Münster
• 2023 - 2024: Universitair hoofddocent (Associate Professor) at the Institute for Logic, Language and Computation of the University of Amsterdam
• From 09/2024: Associate Professor at the University of Münster