  The energy density, the pressure and the anisotropic stress of the relic
gravitons do not have a unique gauge-invariant and frame-invariant expression
since the equivalence principle ultimately forbids the localization of the
energy-momentum of the gravitational field. All the strategies proposed so far
suggest compatible descriptions inside the effective horizon but they lead to
sharply different answers when the wavelengths of the gravitons exceed the
Hubble radius by remaining shorter than the typical extension of causally
connected patches. We present a coherent discussion of the energy-momentum
pseudo-tensors of the relic gravitons in the different kinematical regimes with
the aim of scrutinizing the mutual consistency of the competing suggestions.
The various proposals are systematically compared by deducing and analyzing the
explicit form of the observables in realistic physical situations. General
lessons are drawn on the most plausible parametrization of the energy-momentum
pseudo-tensor of the relic gravitons.
