Interfaces of active fluids

CFM Seminars

Margarida Telo da Gama
Centro de Física Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa
CFM Auditorium
Ivo Souza
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Interfaces of active fluids

CFM Colloquium Series

Many examples of active soft matter (ASM) are biological spanning the length scales of living systems, from self-organizing biopolymers to schools of fish. The force-generating particles of active systems consume energy from the surroundings and its dissipation drives the emergence of hierarchical structures and large-scale collective dynamics.Studies of active matter considered infinite systems and constructed state diagrams by identifying the broken symmetries, under different conditions. However, real systems are bounded and questions such as: What is shape of an active system? How does it fluctuate and what is its stability? How does the surface tension depend on activity? have not been answered.

The simplest class of ASM at the particle level is a system of active Brownian particles (ABPs) described at the hydrodynamic level by (active) model B+ for the dynamics of a conserved scalar order parameter field. Studies revealed surprising collective behaviors, notably phase separation in systems of purely repulsive particles, known as motility induced phase separation (MIPS). Even for these systems fundamental questions such as the scaling of the interfacial fluctuations, at MIPS, were addressed only recently.