Graviton propagator in de Sitter space

We consider the graviton propagator in a de Sitter background. The propagator depends upon the choice of a gauge-fixing term $L_{\mathrm{gauge}=1/2\mathrm{}{F}^2}$, and we consider the ‘‘ε gauges’’ with $F^v$=${\nabla }_u$($h^{\mathrm{uv}}$-ε$g^{\mathrm{uv}}$ $h^{\sigma }$ ${}_{\sigma }$). We show that the propagator is completely finite and has no infrared divergences provided that ε is not given certain ‘‘exceptional’’ values. It is only for these ‘‘exceptional’’ values of ε that the propagator has an infrared divergence. We then show that in these exceptional cases the divergences are gauge artifacts and are not physical: they make no contribution to any physical tree-level scattering amplitudes. Furthermore, we show that at one-loop order the zero modes which arise (only) if ε is given one of the exceptional values are canceled by the Faddeev-Popov ghosts. There is thus no evidence that the de Sitter background is inconsistent when gravitational fluctuations are considered.