Frozen contribution to a de Sitter scalar spectrum ($P_{\mathrm{frozen}}=H^2/(2k^3),{\Delta }_{\mathrm{frozen}}^2=H^2/(4{\pi }^2)$)

The second term in the equal-time two-point function of a de Sitter scalar is independent of time for constant $H$. It dominates on superhorizon scales and has constant dimensionless power spectrum, giving a scale-invariant inflationary power spectrum. The infrared qualification of a scale-invariant covariance still applies to the formally infinite-volume coincident variance.