Description du sujet de thèse

Theory of Active Matter with Non-Reciprocal Interactions

Active matter—systems composed of self-driven units—has become a major interdisciplinary field, spanning physics, biology, and chemistry. While collective behavior in such systems has been widely studied, a crucial aspect remains poorly understood: non-reciprocal interactions, where the action of one particle on another is not equally returned (e.g., predator-prey dynamics, or vision-based interactions). These are common in real-world active systems but largely absent from standard models.

This project aims to explore, at a theoretical level, how non-reciprocal forces impact the macroscopic behavior of dense active systems. Do they generate new phases of matter, or explain large-scale flows seen in experiments? Can they reshape our understanding of non-equilibrium collective phenomena?

We will study simplified but physically grounded models—such as repulsive particles and tissue-inspired Voronoi/Vertex models—combining analytical approaches and numerical simulations. The work will proceed in two stages: first, investigating the emergence of collective motion from non-reciprocal interactions alone; then, incorporating self-propulsion to better match systems like bacterial colonies or epithelial layers. This project offers an exciting opportunity to contribute to cutting-edge research at the frontier of statistical physics and biological physics.

Contexte de travail

The PhD project will take place at the Gulliver Laboratory at ESPCI, located at 10 rue Vauquelin, in the 5th arrondissement of Paris. Ludovic Berthier is an expert in statistical physics, active matter, numerical simulations, and out-of-equilibrium systems. This project will be carried out in close collaboration with members of the Gulliver Lab, as well as with the group of V. Vitelli at the University of Chicago (USA).

Contraintes et risques

This is a theoretical project. No specific security concerns.