GRAVITATIONAL PARTICLE CREATION BY SPHERICAL OSCILLATIONS

The energy flux of particles created by radial oscillations of a spherical shell is calculated in the geometrical optics limit for a massless scalar field with arbitrary curvature coupling. The amplitude of the oscillations, delta , is assumed to be small compared with the equilibrium radius of the shell, R. The outgoing created energy flux is computed through order ( delta /R) for arbitrary curvature coupling and to order ( delta /R)2 for conformal coupling. Such semiclassical particle creation provides a source of radiative dissipation for monopole oscillations for which there is no analogue in classical general relativity. The flux is strictly positive for conformally coupled fields, while for non-conformal coupling, the flux contains a term of oscillating sign of order delta /R. The proposed constraint on negative energy fluxes, namely that F tau 2<1, will hold only if the curvature coupling is restricted in magnitude, mod xi -1/6 mod <or approximately=1.