RADIATION MODES OF A CAVITY WITH A MOVING BOUNDARY

The properties of the quantum vacuum in a one-dimensional cavity with a moving wall are studied. We present a method to obtain an exact solution for the classical electromagnetic potential of a cavity with arbitrary wall motion. This method is applied to a system with a wall oscillating at a harmonic of the cavity resonance frequency. Two factors entirely determine the long-time solution of an undamped system: the points in time at which the wall returns to its initial position, and the direction the wall was displaced in between these points in time. In each of the resonant systems we examined, wave packets in the field energy density formed that become narrower and grow in intensity as time increases. This is the case even when the oscillation frequency of the wall is equal to the fundamental cavity resonant frequency, despite the fact there is no net energy growth in the field of such systems. The number of wave packets, and the long-time limit to the value of the energy density in between the wave packets, are determined by the two factors mentioned above.