Lorenzo Caprini
I developed my academic career in non-equilibrium statistical physics and soft matter, with a focus on active systems, at the crossroad of Physics, Chemistry, and Biology. After obtaining my Ph.D. at Gran Sasso Science Institute (Italy), on the statistical mechanics of self-propelled systems, I continued to work in active matter, with theory and simulations, in particular, discovering a novel dynamical collective effect and collaborating in experiments with spermatozoa. Currently, I am pursuing my research as a Humboldt Fellow at the University of Düsseldorf, with a focus on collective phenomena in dense active matter, experiments based on active granular particles, and numerical simulations for experiments of active colloids. Beyond active matter, I am an expert in the fields of stochastic thermodynamics and linear response theory.
Thursday April 20th
Collective phenomena in active Brownian particles
Systems of active matter extract energy from the environment and convert it into directed motion that is responsible for fascinating collective phenomena. After introducing simple stochastic models, such as active Brownian particles and active Ornstein-Uhlenbeck particles, to describe the behavior of active systems, I will provide an overlook of their collective effects. Purely repulsive active particles show motility induced phase separation, a non-equilibrium coexistence between a low and a high-density phase, that is characterized by the spontaneous alignment between the particles' velocities in the denser phase. Despite the absence of alignment interactions, the system displays spatial velocity correlations which are characterized by an exponential shape and have no passive counterparts. Attractive non-aligning active particles show coarsening and cluster formation, as usual in passive systems, but also the onset of a first-order phase transition from a disordered phase, with small clusters traveling in random directions, to an ordered phase, showing a flocking cluster. In both cases, I will present suitable theoretical predictions supporting the numerical results and explaining how velocity alignment can spontaneously emerge from the interplay between persistent active forces and particle interactions.