Quantum Vacuum Self-Propulsion and Torque

This article summarizes our recent efforts to understand spontaneous quantum vacuum forces and torques, which require that a stationary object be out of thermal equilibrium with the blackbody background radiation. We proceed by a systematic expansion in powers of the electric susceptibility. In first order, no spontaneous force can arise, although a torque can appear, but only if the body is composed of nonreciprocal material. In second order, both forces and torques can appear, with ordinary materials, but only if the body is inhomogeneous. In higher orders, this last requirement may be removed. We give a number of examples of bodies displaying second-order spontaneous forces and torques, some of which might be amenable to observation.