A New Generation of Active Matter Models

ended

The development of non-equilibrium statistical physics has provided a powerful tool to understand and describe the collective dynamics of a wide range of chemical, biological and social systems. In this framework, active matter has raised as one of the most significant topics in this domain, mainly addressing the features of many-body dynamics with self-propelled units such as bacteria colonies, bird flocks and pedestrians walks. Based on the observation of collective motion like size synchronization and wave propagation in epithelial tissues, we will introduce a new class of active matter models to understand the microscopic physical mechanisms underlying these dynamics. Motivated by the physical complexity of biological units, we will extend the concept of activity to the ability of the individual particle to change an internal degree of freedom, related to its size or to an energetic landscape, and we will explore the non-equilibrium phase transitions and collective behavior originating from this property. Our research project consists of three main objectives: (i) we will first extensively investigate the phase diagram of actively deforming particles, and compare it to the experimental observations to capture the essential mechanisms of phase transitions and wave propagation; (ii) we will then explore the interplay between phase synchronization and microscopic energy landscapes to understand the minimal ingredients for liquid-liquid phase separation, where two fluids spontaneously separate from a mixed phase; (iii) we will finally study the energetics of these models, quantifying the energy gain/cost of each phase and studying how phase transitions can be optimized. The exploration of these models represents a potential breakthrough in the physics of soft matter, clarifying the microscopic ingredients at the basis of several chemical and biological dynamics and introducing a fertile ground for the emergence of new physics.