  The existence of cosmological perturbations of wavelength larger than the
Hubble radius is a generic prediction of the inflationary paradigm. We provide
the derivation beyond perturbation theory of a conserved quantity which
generalizes the linear comoving curvature perturbation. As a by-product, we
show that super-Hubble-radius (super-Hubble) perturbations have no physical
influence on local observables e.g., the local expansion rate) if cosmological
perturbations are of the adiabatic type.
