Switching of non-equilibrium depletion force caused by blockade effect

TL;DR

This paper investigates how non-equilibrium depletion forces between obstacles in a Brownian gas can switch signs due to blockade effects, with concentration-dependent wake inversion leading to interaction changes.

Contribution

It reveals the mechanism of force switching caused by blockade effects and demonstrates this phenomenon using a lattice gas model in mean-field approximation.

Findings

Gas concentration influences wake inversion and force sign change.

Blockade effects cause obstacle wake profile turn-over.

Non-linear effects include cavity-like wakes and dissipative pairing.

Abstract

The concentration-dependent switching of the non-equilibrium depletion forces between obstacles in an interacting Brownian gas flow is presented. It is shown that this switching is caused by the blockade effect for the gas particles. With increasing equilibrium gas concentration, the gas particles blockade causes the obstacle wake inversion (trace profile turn-over) that, in turn, leads to the change of sign of dissipative interaction. Some non-linear effects such as formation of a cavity-like sparse wake behind the obstacle and the dissipative pairing effect are discussed briefly. The results are obtained within the lattice gas model in the mean-field approximation.