EXPONENTIAL-GROWTH OF THE ENERGY OF A WAVE IN A 1D VIBRATING CAVITY -APPLICATION TO THE QUANTUM VACUUM

The wave equation in a one-dimensional cavity is equivalent to the mot ion of massless particles in a two-dimensional space-time billiard. Th is allows us to consider, in a simple way, the case of a cavity with o ne or two oscillating walls. It is shown that a set of continuous fami lies of frequencies of the oscillating walls leads to an exponential g rowth of the energy of a wave. For such cases, the wave energy is loca lized in narrow space regions moving at the wave velocity. As a conseq uence the electromagnetic vacuum fluctuations inside the cavity increa se exponentially and the possibility to observe experimentally photon creation from the vacuum could be reconsidered.