Claudio Maggi — CNR-Nanotec - Roma #
Continuous phase transitions in active particles systems #
In this talk I will review some recent results regarding continuous phase transition in active particles systems. In the first part of the talk I will focus on simulations of active particles interacting via a quorum-sensing (QS) mechanism by which particles change their swimming speed based on the number of perceived neighbors. I will show that if these particles slow down enough when interacting, the system undergoes a full motility-induced separation (MIPS) and that the coexistence curve terminates into a critical point belonging to the Ising universality class [1]. In contrast I will also show recent results demonstrating that, if these QS interactions have two competing scales, the MIPS is destabilized and the system forms an active micro-emulsion which is well described by a renormalized field-theory in a effective equilibrium framework. Finally I will discuss some recent experiments in which super-paramagnetic colloids activated by a bath of swimming E. coli undergo two-dimensional melting out of equilibrium [2]. I will show how the basic physics of the experimental active crystal is well reproduced by a schematic model of active particles and how the KTHNY-theory remains qualitatively valid in describing the melting scenario of this active solid. [1] N.Gnan and C. Maggi Soft Matter 18, 7654 (2022) [2] H. Massana-Cid, C. Maggi et al. arXiv:2401.09911 (2024)