= Monomial-inflation curvature amplitude
{title2=$\mathcal P_{\mathcal R}=V/(24\pi^2M_{\rm Pl}^4\epsilon_V)$}
For $V=C_p(\Phi/M_{\rm Pl})^p$ and the leading endpoint estimate $\epsilon_V=1$, the <slow-roll approximation> gives $\Phi_N^2/M_{\rm Pl}^2=2pN+p^2/2$ and $\epsilon_V=p/(4N+p)$. Thus $\mathcal P_{\mathcal R}=C_p(2pN+p^2/2)^{p/2}(4N+p)/(24\pi^2M_{\rm Pl}^4p)$ and the <scalar spectral index> obeys $n_s-1=-2(p+2)/(4N+p)$. The coefficient sets the amplitude, whereas the monomial power and exit e-fold count set the leading tilt. Changing the power without specifying the coefficient leaves the overall normalization undetermined.
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