Sonoluminescence as quantum vacuum radiation

Sonoluminescence is explained in terms of quantum vacuum radiation by moving interfaces between media of different polarizability. It can be considered as a dynamic Casimir effect, in the sense that it is a consequence of the imbalance of the zero-point fluctuations of the electromagnetic field during the noninertial motion of a boundary. The transition amplitude from the vacuum into a two-photon state is calculated in a Hamiltonian formalism and turns out to be governed by the transition matrix element of the radiation pressure. Expressions for the spectral density and the total radiated energy are given.