Induced gravitational waves from slow-roll inflation after an enhancing
  phase
  The primordial spectrum of fluctuations may present a large peak as a result
of enhancing features during inflation. This may include, but is not limited
to, bumps in the inflaton's potential, phases of ultra-slow-roll or turns in
multi-field space. However, in many models, inflation does not end immediately
after the enhancing feature and it is likely to continue with a second phase of
slow-roll. We show that the resulting induced gravitational waves may probe the
primordial spectrum from the second inflationary phase, even if its amplitude
is too small to directly induce detectable gravitational waves. This is
because, if there are sharp peaks in the primordial spectrum, the total
gravitational wave spectrum is not simply the sum of gravitational waves
induced by a peaked and scale-invariant primordial spectra separately, but
cross terms from interaction between these modes also become important. We also
find that such cross terms always have a characteristic slope. We discuss the
parameter space that may be probed by future gravitational waves detectors in
the presence of these signals.
