2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/220463The cosmological background of gravitational waves can be tuned by Extended Theories of Gravity. In particular, it can be shown that assuming a generic function $f(R)$ of the Ricci scalar $R$ gives a parametric approach to control the evolution and the production mechanism of gravitational waves in the early Universe.5 pages, to appear in the Proceedings of the 3rd Stueckelberg Workshop, July 2008, Pescara - ItalyGeneral Relativity and Quantum Cosmologytext