Charlotte (Amann-)Bartnick

[Bild Charlotte Bartnick]

About me:

I am a PhD Student in the department of Mathematical Logic under the supervison of Prof. Dr. Amador Martin-Pizarro. I am interested in geometric stability theory, definable groups in stable and simple theories as well as theories of fields with operators.

Contact

The best way to contact me is via mail.

Mail: charlotte[dot]bartnick[at]math[dot]uni-freiburg[dot]de
Phone 0049 761 / 203 5611
Room: 305

Full adress:

Abteilung für Mathematische Logik
Albert-Ludwigs-Universität Freiburg
Ernst-Zermelo-Straße 1
79104 Freiburg i. Br.
Germany

Publications and preprints

  • Stationarity and elimination of imaginaries in stable and simple theories, Fund. Math. 270 (2025), no.3, 277-299, DOI: 10.4064/fm241209-15-4, see also ArXiv 2406.16586 (2025): We show that types over real algebraically closed sets are stationary, both for the theory of separably closed fields of infinite degree of imperfection and for the theory of beautiful pairs of algebraically closed field. The proof is given in a general setup without using specific features of theories of fields.
    Moreover, we generalize results of Delon as well as of Messmer and Wood that separably closed fields of infinite degree of imperfection and differentially closed fields of positive characteristic do not have elimination of imaginaries. Using work of Wagner on subgroups of stable groups, we obtain a general criterion yielding the failure of geometric elimination of imaginaries. This criterion applies in particular to beautiful pairs of algebraically closed fields, giving an alternative proof of the corresponding result of Pillay and Vassiliev.
  • Embedding stable groups into algebraic groups, preprint, ArXiv 2510.24504 (2025): Adapting a proof of Bouscaren and Delon, we show that every type-definable connected group in a given stable theory of fields embeds into an algebraic group, under a condition on the definable closure. We also present general hypotheses which yield a uniform description of the definable closure in such theories of fields.
    The setting includes in particular the theories of separably closed fields of arbitrary degree of imperfection and differentially closed fields of arbitrary characteristic.

Teaching assistance:

PhD Representation

I am one of the five PhD Representatives of the Faculty of Mathematics and Physics. We try to connect the PhD students by organizing social events and to improve their conditions as doctoral researchers. Further information on our work can be found here: https://www.phd.mathphys.uni-freiburg.de/.