Boundary symmetry breaking in polar active matter - Giuseppe Fava - Young Seminars SIFS скачать в хорошем качестве

Boundary symmetry breaking in polar active matter - Giuseppe Fava - Young Seminars SIFS

Boundary symmetry breaking in polar active matter Giuseppe Fava, University of Insubria Abstract: Active matter, i.e., nonequilibrium systems capable of transforming some non-thermal energy present in the environment into self-propulsion or other functional mechanisms, has attracted the attention of the statistical physics community in the past decades. Flocking is perhaps one of the most intriguing examples of collective behaviors exhibited by active matter systems, as shown by the aerial displays of starling flocks. While our knowledge of the bulk behavior of free collective motion, i.e. flocking, is now fairly complete, at least when the surrounding fluid may be safely neglected (the so-called dry approximation) much less is known when collective motion is achieved explicitly breaking a continuous rotational symmetry. In this seminar I will present the effects of boundary symmetry breaking on the dynamics of collective motion: in confined flocking systems, local anisotropies can arise at the boundaries, which significantly affect both the bulk and boundary behavior of the system. We will show that a confined vectorial active fluid is indeed characterized by extensive boundary layers where particles accumulate and which are a consequence of the long-range correlations of fluctuations, present in all of the ordered flocking phase. We will also show how, as a further consequence, these also induce a Casimir-like force on the confining walls. Remarkably both these results hold generically in all the homogeneous polar liquid phase, even beyond the strict dilute limit, showing a certain degree of universality. Reference: [1] Fava, G., Gambassi, A., & Ginelli, F. (2024). Strong Casimir-like forces in flocking active matter. Physical Review Letters, 133(14), 148301.[2] Lenzini, L., Fava, G., & Ginelli, F. (2024). Boundary symmetry breaking of flocking systems. Journal of Statistical Mechanics: Theory and Experiment, 2024(8), 083210. #YSSIFS