# ANR Project AGRUME – Group actions and model theory

coordinated by Itaï Ben Yaacov

## Description

The main goal of the project is to study interactions between dynamical systems and model theory. We are going to concentrate on four main themes:

- Relations between Ramsey properties of a Fraïssé class and topological dynamical properties of the automorphism group of the Fraïssé limit. One of our main goals is to find a useful sufficient condition for an automorphism group to have a metrisable universal minimal flow (which will have many Ramsey-theoretic applications).
- A model-theoretic approach to ergodic theory. We are intersted in applications of continuous logic to ergodic theory and orbit equivalence. One of our main goals is to develop a model-theoretic approach to the theory of entropy (for both amenable and non-amenable groups).
- Correspondences between model-theoretic properties (of structures, or formulas) and dynamical properties (of automorphism groups, or of functions defined on them). In particular, the extension of several existing such correspondences beyond the ω-categorical setting, or beyond the discrete setting.
- A study of the normal subgroup structure of automorphism groups. In particular, the study of the subgroup of “bounded automorphisms”, and its subgroups, both in several specific cases and under general hypotheses.

## Announcements and events

- Post-doctoral positions available, deadline January 1st. Click here for the announcement.

## Members

The project has two nodes, based in Lyon and in Paris.

### Lyon

- Tuna Altınel (Univ. Lyon 1)
- Itaï Ben Yaacov (Univ. Lyon 1), coordinator of the project
- Thomas Blossier (Univ. Lyon 1)
- Charlotte Hardouin (Toulouse)
- Julien Melleray (Univ. Lyon 1)
- Lionel Nguyen Van Thé (Aix-Marseille)
- Frank Wagner (Univ. Lyon 1)

### Paris

- Élisabeth Bouscaren (CNRS, Univ. Paris Sud)
- Zoé Chatzidakis (CNRS, ENS Paris)
- Tomás Ibarlucía (Univ. Paris Diderot)
- François Le Maître (Univ. Paris Diderot)
- Jordi López-Abad (Madrid)
- Todor Tsankov (Univ. Paris Diderot), coordinator of the node