On the generation mechanism of gravitational waves in the vicinity of a black hole

We discuss the nature of gravitational radiation mechanism in the case of perturbations caused by a test particle moving along a geodesic in a black hole geometry. We develop a semirelativistic approximation scheme which is intended for extracting the locally definable part of radiation from the total. Comparing the results obtained by this method with those of fully relativistic calculations available in literature, we consider the excitation mechanism for the quasi-normal mode oscillations of a black hole. We find a black hole can be regarded as a very flexible elastic body for which the oscillations are easily induced and once they are induced they are amplified as a masor and generate a large amount of outgoing radiation. (author)