A New Generation of Active Matter Models

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.