Inertia changes evolution of motility-induced phase separation in active matter across particle activity

The effects of inertia in active matter and motility-induced phase separation (MIPS) have attracted growing interest but still remain poorly studied. We studied MIPS behavior in the Langevin dynamics across a broad range of particle activity and damping rate values with molecular dynamic simulations. Here we show that the MIPS stability region across particle activity values consists of several domains separated by discontinuous or sharp changes in susceptibility of mean kinetic energy. These domain boundaries have fingerprints in the system's kinetic energy fluctuations and characteristics of gas, liquid, and solid subphases, such as the number of particles, densities, or the power of energy release due to activity. The observed domain cascade is most stable at intermediate damping rates but loses its distinctness in the Brownian limit or vanishes along with phase separation at lower damping values.

Automated summary

The effects of inertia and motility-induced phase separation (MIPS) in active matter have gained attention, but are still poorly understood. Through molecular dynamic simulations, we investigated MIPS behavior in Langevin dynamics across a wide range of particle activity and damping rate values. Our results show that the MIPS stability region consists of multiple domains separated by abrupt changes in susceptibility of mean kinetic energy. These domain boundaries are reflected in the system's kinetic energy fluctuations and properties of gas, liquid, and solid phases. The observed cascade of domains is most stable at intermediate damping rates, but disappears in the limit of Brownian motion or along with phase separation at lower damping values.