Science with the space-based interferometer LISA. IV: Probing inflation with gravitational waves

We investigate the potential for the LISA space-based interferometer to detect the stochastic gravitational wave background produced from different mechanisms during in ation. Focusing on well-motivated scenarios, we study the resulting contributions from particle production during in ation, in ationary spectator fields with varying speed of sound, effective field theories of in ation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes. The projected sensitivities of LISA are used in a model-independent way for various detector designs and configurations. We demonstrate that LISA is able to probe these well-motivated in ationary scenarios beyond the irreducible vacuum tensor modes expected from any in ationary background.