Abstract
The collective response of relativistic isotropic plasmas to external fields and particles is investigated. The collisionless relativistic Vlasov equation is solved in the usual manner and a dielectric tensor relating the long-time total and external fields is obtained. The relativistic Maxwellian plasma is studied in detail and graphs of longitudinal and transverse dielectric functions are given. The collective energy loss rate of a relativistic test particle is also examined and numerical results for the case of a relativistic Maxwellian distribution function are displayed.