= Quadratic-inflation endpoint estimate
{title2=$\phi_{\rm end}\simeq m_P/\sqrt{4\pi}$}
For $V=m^2\phi^2/2$ and unreduced <Planck mass> $m_P=G^{-1/2}$, the <potential slow-roll parameter> is $\epsilon_V=m_P^2(V'/V)^2/(16\pi)=m_P^2/(4\pi\phi^2)$. Its conventional value one gives the displayed endpoint estimate. Exact accelerated expansion ends at $\epsilon_H=1$, or $\dot\phi^2=V$ for a canonical scalar alone. Substitution of slow-roll formulas into this exact condition gives a different order-one coefficient because slow roll is failing there; a precise endpoint requires integrating the full <inflaton equation of motion> and <Friedmann equation>. The large-field e-fold estimate is insensitive to this order-one endpoint uncertainty.
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