= Exponential-potential scalar-dominated power-law solution
{title2=$a\propto t^{2/\lambda^2},\quad\varphi=(2M_{\rm Pl}/\lambda)\log(t/t_0)$}
For $V=V_0e^{-\lambda\varphi/M_{\rm Pl}}$, $\lambda\ne0$, the displayed ansatz satisfies the flat <Friedmann equation> and <scalar field equation of motion> when $V_0t_0^2=2M_{\rm Pl}^2(6-\lambda^2)/\lambda^4$. Its <equation-of-state parameter> is $w=-1+\lambda^2/3$ and its <deceleration parameter> is $q=\lambda^2/2-1$. It gives <exponential-potential power-law inflation> only for $0<\lambda^2<2$; the same algebraic family includes decelerating expansion outside that range when its potential normalization is real.
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