A New Generation of Active Matter Models

Ziel

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.