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 points can be generated a polynomial potential or Higgs like $\phi^4$ running quartic coupling.In such models, point at large scales predicts spectral index and tensor-to-scalar ratio consistent current CMB constraints, other two generate power small scales, which GWs energy spectrum. find that for some choices parameters detected by future GW detectors, one around $f\simeq10^{-9}\sim10^{-8}$Hz also explain recent NANOGrav signal. Moreover, allow generation black holes, account significant fraction dark matter.