“…From the CMB observations one obtains the allowed region at the pivot scale k = k * =0.05 Mpc −1[934,33]. The green, orange, and brown regions are excluded by the µ-distortion of the CMB spectrum[884,885,886,887,93], secondary GWs[882,915,883,93], and the dilution of baryons (or the n/p ratio) after BBN[895,896,897], respectively. The lines in the figure are from Ref [93]…”