Double peaks of gravitational wave spectrum induced from inflection
  point inflation
  We investigate the possibility to induce double peaks of gravitational
wave(GW) spectrum from primordial scalar perturbations in inflationary models
with three inflection points.Where the inflection points can be generated from
a polynomial potential or generated from Higgs like $\phi^4$ potential with the
running of quartic coupling.In such models, the inflection point at large
scales predicts the scalar spectral index and tensor-to-scalar ratio consistent
with current CMB constraints, and the other two inflection points generate two
large peaks in the scalar power spectrum at small scales, which can induce GWs
with double peaks energy spectrum. We find that for some choices parameters the
double peaks spectrum can be detected by future GW detectors, and one of the
peaks around $f\simeq10^{-9}\sim10^{-8}$Hz can also explain the recent NANOGrav
signal. Moreover, the peaks of power spectrum allow for the generation of
primordial black holes, which account for a significant fraction of dark
matter.
