Active phase field crystal systems with inertial delay and underdamped dynamics.

Area of Science:

• Physics
• Soft Matter Physics
• Nonlinear Dynamics

Background:

• Active matter systems are often modeled as overdamped, neglecting particle inertia.
• However, particle mass can be crucial for dynamics in mesoscopic and macroscopic systems.
• An underdamped continuum model incorporating translational inertia was recently proposed.

Purpose of the Study:

• To investigate the influence of inertial dynamics on collective behavior in active matter.
• To compare underdamped dynamics with traditional overdamped models.
• To analyze the roles of convection and damping time in inertial active matter.

Main Methods:

• Studied the active phase field crystal model as an example system.
• Analyzed an underdamped continuum model with contributions from convection and damping time.
• Focused initially on suppressed convection to isolate the effect of damping time.
• Examined the fully underdamped case including convection.

Main Results:

• Increased damping time significantly prolongs relaxation to steady collective motion.
• Transient groups of circularly moving density peaks emerge with longer damping times.
• In the fully underdamped case with convection, motility-induced phase separation occurs, showing distinct high and low-density phases.

Conclusions:

• Inertia, specifically damping time and convection, fundamentally alters active matter collective behavior.
• Underdamped dynamics lead to phenomena not observed in overdamped approximations, such as phase separation.
• The proposed underdamped model provides a richer description of active matter dynamics.