Backreaction of superhorizon scalar field fluctuations on a de Sitter geometry : a renormalisation group perspective

Understand

We study the backreaction of gravitationally amplified quantum fluctuations of scalar fields on a classical de Sitter geometry.

• We formulate the problem in the framework of the Wilsonian renormalisation group, which allows us to treat the scalar field fluctuations in a nonperturbative manner and to follow the renormalisation flow of the spacetime curvature as long wavelength, superhorizon fluctuations are progressively integrated out.
• For light fields in units of the spacetime curvature, these are described by an effective zero-dimensional field theory and can essentially be computed analytically.
• A nontrivial flow of the spacetime curvature is induced either by a nonminimal coupling to gravity or by self-interactions.