Constant primordial bispectrum
= Constant primordial bispectrum
{title2=$B\propto(k_1k_2k_3)^{-2}$}
A constant <primordial bispectrum> means a constant <bispectrum shape function>, not a bispectrum independent of wavenumber. With $P(k)=2\pi^2\Delta_\zeta^2/k^3$ and scale-independent $\Delta_\zeta^2$, one normalization is $B=f_{\rm NL}[P(k_1)P(k_2)P(k_3)]^{2/3}=4\pi^4f_{\rm NL}\Delta_\zeta^4/(k_1k_2k_3)^2$.