Normal modes of a model radiating system (Q1077953)

In order to gain insight into normal modes of realistic radiating systems, we study the simple model problem of a finite string and a semi- infinite string coupled by a spring. As expected there is a family of modes which are basically the modes of the finite string slowly damped by the ''radiation'' of energy to infinity on the semi-infinite string. But we also study another family of modes, which are strongly damped modes of the semi-infinite string itself. These may be analogous to the modes of black holes, and they are likely to be present in relativistic stars as well. The question of whether the instability in these modes is present in realistic stars remains open.