91福利

Active matter is a class of non-equilibrium systems where energy is injected to the system continuously by the constituent particles themselves. Many examples of active matter are biological in nature, for example, bird flocks, bacterial suspensions and biological tissues. In the case of bacterial suspensions, the fluid solvent is continuously stirred by the swimming motion of the bacteria, driving it out-of-equilibrium. Active matter is an interesting class of non-equilibrium systems because it often displays large-scale time reversal symmetry breakdown at steady state. For example, when we put an asymmetric gear into a bath full of bacteria, the gear will start to rotate in one direction at steady state. This is a manifestation of large-scale time reversal symmetry breaking because if we reverse the arrow of time, the gear will rotate in the other direction. In this talk, I will present a simple scalar field theory which can capture such large-scale time reversal symmetry breaking.