Friday, May 17th, 14h00, Room 454 A, Condorcet Building.

PhD defense of Gianmarco Spera
From Active Particles to Cells: A Journey Beyond Simple Active Matter.

supervised by Marc Durand, François Graner and Julien Tailleur

Abstract:
Active matter describes systems comprising elementary units able to exert non-conservative forces on their environment. This momentum injection at the single unit level drives the system out of equilibrium, resulting in various patterns across all scales, from molecular motors to humans, passing through cells, fish, and birds. Cellular systems have naturally received much attention due to their biological relevance and the theoretical challenges of modeling their complexity. Compared to colloidal active particles, cells can deform, fluctuate, adapt, and communicate in ways inaccessible to synthetic units. Nonetheless, an interesting question is whether biological cells can be modeled using the active particles model. During my thesis, we study different problems to get closer to this goal by proceeding in two directions: the study of less simple active-matter models and a direct comparison between particle and cellular models.
Concerning complex active matter, we proceeded in four directions: the impact of nematic torques on scalar active matter, phase separation in the presence of aligning interactions, the transition to collective motion for particles aligning with their Voronoi neighbours, and the impact of different taxis mechanisms on active systems. Finally, to directly compare active particles and cellular systems, we studied the concept of pressure in cellular systems.