On Infrared Effects in de~Sitter Background
  We have estimated higher order quantum gravity corrections to de~Sitter spacetime. Our results suggest that, while the classical spacetime metric may be distorted by the graviton self-interactions, the corrections are relatively weaker than previously thought, possibly growing like a power rather than exponentially in time. 
A. D. Dolgov, M. B. Einhorn, and V. I. Zakharov