Vacuum torque, propulsive forces, and anomalous tangential forces: Effects of nonreciprocal media out of thermal equilibrium

TL;DR

This paper investigates how nonreciprocal materials out of thermal equilibrium can experience vacuum-induced torques and forces, revealing potential observable effects and limitations in their application.

Contribution

It analyzes the emergence of torque and lateral forces on nonreciprocal bodies near surfaces, extending understanding of non-equilibrium fluctuation-induced phenomena.

Findings

Nonreciprocal bodies can experience vacuum torque out of thermal equilibrium.

Lateral forces can arise when near surfaces with translational symmetry.

Observable effects are possible despite theoretical limitations.

Abstract

From the generalized fluctuation-dissipation theorem, it is known that a body at rest made of nonreciprocal material may experience a torque, even in vacuum, if it is not in thermal equilibrium with its environment. However, it does not experience self-propulsion in such circumstances, except in higher order. Nevertheless, such a body may experience both a normal torque and a lateral force when adjacent to an ordinary surface with transverse translational symmetry. We explore how these phenomena arise, discuss what terminal velocities might be achieved, and point out some of the limitations of applying our results to observations, including the Lorenz-Lorentz correction, and the cooling due to radiation. In spite of these limitations, the effects discussed would seem to be observable.