  The propagators for the Faddeev-Popov (FP) ghosts in Yang-Mills theory and
perturbative gravity in the covariant gauge are infrared (IR) divergent in de
Sitter spacetime. An IR cutoff in the momentum space to regularize these
divergences breaks the de Sitter invariance. These IR divergences are due to
the spatially constant modes in the Yang-Mills case and the modes proportional
to the Killing vectors in the case of perturbative gravity. It has been
proposed that these IR divergences can be removed, with the de Sitter
invariance preserved, by first regularizing them with an additional mass term
for the FP ghosts and then taking the massless limit. In the Yang-Mills case,
this procedure has been shown to correspond to requiring that the physical
states, and the vacuum state in particular, be annihilated by some conserved
charges in the Landau gauge. In this paper we show that there are similar
conserved charges in perturbative gravity in the covariant Landau gauge in de
Sitter spacetime and that the IR-regularization procedure described above also
correspond to requiring that the vacuum state be annihilated by these charges
with a natural definition of the interacting vacuum state.
