Eliminating infrared divergences in an inflationary cosmology

Understand

We study the infrared divergences arising from gravitational loops in the standard cosmological perturbation theory.

• We provide a simple solution to the problem at all orders of cosmological perturbation theory by redefining the perturbation theory in terms of a local observer.
• We propose to reformulate the standard perturbations in the in-in formalism, and obtain an infrared safe perturbation theory.
• Our results do not depend on any infrared cutoffs or similar parameters.