Gravitational waves, inflation and the cosmic microwave background: towards testing the slow-roll paradigm

One of the fundamental and yet untested predictions of inflationary models is the generation of a very weak cosmic background of gravitational radiation. We investigate the sensitivity required for a space-based gravitational wave laser interferometer with peak sensitivity at ∼1 Hz to observe such signal as a function of the model parameters and compare it with indirect limits that can be set with data from present and future cosmic microwave background missions. We concentrate on signals predicted by slow-roll single-field inflationary models and instrumental configurations such as those proposed for the LISA follow-on mission: big bang observer