Comment on ``Sonoluminescence as Quantum Vacuum Radiation''

We argue that the available experimental data is not compatible with models of sonoluminescence which invoke dynamical properties of the interface without regard to the compositional properties of the trapped gas inside the bubble.

The insufficiency of the energy radiated in the model of Eberlein is discussed.

Reply to Comments by Lambrecht, Jaekel, and Reynaud, and by Garcia and Levanyuk, submitted to Physical Review Letters.

Sonoluminescence is explained in terms of quantum radiation by moving interfaces between media of different polarizability. In a stationary dielectric the zero-point fluctuations of the electromagnetic field excite virtual two-photon states which become real under perturbation due to motion of the dielectric. The sonoluminescent bubble is modelled as an optically empty cavity in a homogeneous dielectric. The problem of the photon emission by a cavity of time-dependent radius ...

The Spectrum of the light emitted by a sonoluminescing bubble is extremely well fit by the spectrum of a blackbody. Furthermore the radius of emission can be smaller than the wavelength of the light. Consequences, for theories of sonoluminescence are discussed.

Several years ago Schwinger proposed a physical mechanism for sonoluminescence in terms of photon production due to changes in the properties of the quantum-electrodynamic (QED) vacuum arising from a collapsing dielectric bubble. This mechanism can be re-phrased in terms of the Casimir effect and has recently been the subject of considerable controversy. The present paper probes Schwinger's suggestion in detail: Using the sudden approximation we calculate Bogolubov coefficien...

We are discussing Schwinger'idea that physical mechanism of sonoluminescence is a physical vacuum excitation. This theory was based on the assumption that the sudden change of the rate of bubble collapse leads to the jump of dielectric constant of the gas trapped inside the bubble. We show that the dependence of the dielectric constant on the gas density really leads to the jump of the dielectric constant at shock-wave propagation in a collapsing gas bubble.

According to the recent revision of the theory of thermal radiation, thermal black-body radiation has an induced origin. We show that in single-bubble sonoluminescence thermal radiation is emitted by a spherical resonator, coincident with the sonoluminescing bubble itself, instead of the ensemble of elementary resonators emitting thermal black-body radiation in the case of open gaseous media. For a given wavelength, the diameter of the resonator is fixed, and this explains th...

In this talk I shall describe an extension of the quantum-vacuum approach to sonoluminescence proposed several years ago by J.Schwinger. We shall first consider a model calculation based on Bogolubov coefficients relating the QED vacuum in the presence of an expanded bubble to that in the presence of a collapsed bubble. In this way we shall derive an estimate for the spectrum and total energy emitted. This latter will be shown to be proportional to the volume of space over wh...

A cavitation bubble inside a liquid, under a specific set of conditions, can get trapped in an antinode of the ultrasonically driven standing wave and periodically emits visible photons (1,2). This conversion of sound to light phenomenon, known as sonoluminescence, can be seen with unaided eyes and occurs in multi- or single-bubble regimes. The sonoluminescence radiation spectrum analysis attributes a temperature of about 6,000 Kelvin to the bubble (3-5) -- close to the sun's...