Dynamical Casimir effect in a cavity with a weakly non-equidistant spectrum

We study the influence of the non-equidistancy of the frequency spectrum on the Dynamical Casimir effect in a rectangular cavity with a harmonically oscillating ideal wall. The transition from the linear growth of the mean photon number of photons created from vacuum in the cavity with equidistant spectrum to the exponential growth in a weakly non-equidistant case is shown explicitly.

► We consider the dynamical Casimir effect in different rectangular cavities.
► One-dimensional models predict the linear growth of the number of photons.
► Three-dimensional models predict the exponential growth.
► We show how one model is transformed continuously into the other.
► The key parameter is the degree of non-equidistancy of the frequency spectra.