Generalized hydrodynamics of active polar suspensions

TL;DR

This paper develops a hydrodynamic theory for active polar suspensions with internal structure and torque, revealing how activity influences stress, angular momentum, and thermodynamics at the continuum level.

Contribution

It introduces a generalized hydrodynamic framework for active matter with internal torque, deriving exact microscopic expressions and highlighting the role of activity in stress symmetry breaking.

Findings

Explicit stress tensor symmetry breaking due to activity.

Derivation of microscopic expressions for stress and energy.

Framework for thermodynamics of active matter.

Abstract

We utilize a generalized Irving-Kirkwood procedure to derive the hydrodynamic equations of an active matter suspension with internal structure and driven by internal torque. The internal structure and torque of the active Brownian particles give rise to a balance law for internal angular momentum density, making the hydrodynamic description a polar theory of continuum mechanics. We derive exact microscopic expressions for the stress tensor, couple stress tensor, internal energy density, and heat flux vector. Unlike passive matter, the symmetry of the stress tensor is broken explicitly due to active internal torque and the antisymmetric component drives the internal angular momentum density. These results provide a molecular basis to understand the transport characteristics and collectively provide a strategy to develop the theory of linear irreversible thermodynamics of active matter.