Quantum electrodynamics in the presence of moving bodies

Abstract

The vacuum state of the electromagnetic field close to a dielectric body is not the same in all reference frames. Here we show that this has some surprising consequences. For instance, if we attempt to quantize electromagnetism interacting with a uniformly moving medium (properly including effects of dispersion and dissipation), then the resulting Hamiltonian lacks a lower bound. Consequently, a detector placed close to a moving surface can be excited by the vacuum! It is shown that when the dielectric is allowed to change velocity then the Hamiltonian again becomes bounded from below, thus demonstrating that the source of the energy exciting the detector is the kinetic energy of the dielectric.