= Vacuum domination by a scalar field
{title2=$\dot\phi^2/2\ll V(\phi)$}
A homogeneous canonical <scalar field> with positive <scalar potential> has <energy density> $\rho_\phi=\dot\phi^2/2+V$ and <pressure> $P_\phi=\dot\phi^2/2-V$. When its <potential energy> dominates its <kinetic energy>, the <equation-of-state parameter> approaches $-1$. If other components and spatial curvature are negligible, the <Friedmann acceleration equation> gives <accelerating expansion>. Small initial <kinetic energy> is not enough to ensure long <cosmic inflation>; the field must also remain on a sufficiently flat part of the <scalar potential>, as measured by the <potential slow-roll parameters>.
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