Solution
= Solution
The homogeneous <inflaton> obeys
$$
\ddot\phi+3H\dot\phi+V'(\phi)=0.
$$
Under the <slow-roll approximation>, the acceleration and kinetic-energy corrections may be neglected, so the field equation and <Friedmann equation> become
$$
3H\dot\phi\simeq-V'=m^2\phi,
\qquad
H^2\simeq\frac{V}{3M_{\rm Pl}^2}
\simeq\frac{\Lambda^4}{3M_{\rm Pl}^2}.
$$
\b[Thus a positive field rolls away from the hilltop while $H$ is approximately constant.]