Directed motion and useful work from an isotropic nonequilibrium distribution

Abstract

We demonstrate that a gas of classical particles trapped in an external asymmetric potential undergoes a quasiperiodic motion, if the temperature of its initial velocity distribution $T_{ne}$ differs from the equilibrium temperature, $T_{eq}$. The magnitude of the effect is determined by the value of $T_{ne}-T_{eq}$, and the direction of the motion is determined by the sign of this expression. The "loading'' and "unloading'' of the gas particles change directions of their motion, thereby creating a possibility of shuttle-like motion. The system works as a Carnot engine where the heat flow between kinetic and potential parts of the nonequilibrium distribution produces the useful work.