Pressure and diffusion of active matter with inertia

Area of Science:

• Physics
• Soft Matter Physics
• Statistical Mechanics

Background:

• Active matter systems exhibit unique physical quantities like swim pressure, arising from momentum exchange.
• This phenomenon occurs across various scales, from microorganisms to larger organisms.
• Inertia becomes significant for larger entities or at high speeds, necessitating its consideration.

Purpose of the Study:

• To analytically investigate the impact of finite translational and rotational inertia on active Brownian particles.
• To determine how inertia affects diffusion, persistence length, and reorientation times.
• To analyze the influence of inertia on bulk properties, specifically swim and Reynolds pressures.

Main Methods:

• Analytical calculations of particle diffusion considering finite inertia.
• Identification of enhanced diffusion coefficients and modified dynamic parameters (persistence length, reorientation time).
• Calculation of swim and Reynolds pressures to assess bulk property changes.
• Validation through Langevin dynamics simulations.

Main Results:

• Finite translational and rotational inertia enhance the diffusion coefficient of active Brownian particles.
• Rotational inertia introduces alternative effective persistence lengths and reorientation times.
• The sum of swim and Reynolds pressures becomes sensitive to the square root of rotational inertia.
• Analytical predictions show excellent agreement with simulation results.

Conclusions:

• Finite inertia, particularly rotational inertia, significantly modifies the dynamic and bulk properties of active matter systems.
• The study provides a theoretical framework and simulation-based validation for understanding inertia effects in active Brownian particles.
• These findings are crucial for accurately modeling active matter behavior where inertia is non-negligible.