Relativistic dynamics of spherical counter-rotating dust bodies

Spherically symmetric dust clusters, of the type first proposed by Einstein, are generalized to nonstationary cases. Particular attention is paid to a massive shell of particles orbiting a central body, using a method developed by Israel (Nuovo Cimento; 44B:1 (1966)). Shells provide comparisons with Schwarzschild test particles, and offer as well a simplified approach to continuously distributed clusters. (author)