2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/149488We give a derivation of the particle-hole RPA equations for an interacting multi-fermion system by applying the instantaneous approximation to the amputated two-fermion propagator of the system. In relativistic field theory the same approximation leads from the fermion-antifermion Bethe-Salpeter equation to the Salpeter equation. We show that RPA equations and Salpeter equation are indeed equivalent.6 pages, RevTeX, Bonn TK-93-19Nuclear TheoryHigh Energy Physics - Phenomenologytext