Primordial GWs from universality classes of pseudo-scalar inflation
  In this contribution we discuss the possibility of generating an observable
gravitational wave (GW) background by coupling a pseudo-scalar inflaton to some
Abelian gauge fields. This analysis is performed by dividing inflationary
models into universality classes. We find that of the most promising scenario
is a Starobinsky-like model, which may lead to the generation of observational
signatures both in upcoming CMB detectors as well as for direct GW detectors.
The signal which can be produced in these models would both be observable in
ground-based detectors, such as advanced LIGO, and in space-based detectors,
such as LISA. The complementarity between the CMB and direct GW detection may
be used to extract informations on the microphysics of inflation. Interestingly
the mechanism discussed in this contribution may also be relevant for the
generation of Primordial Black Holes (PBHs).
