Quantum scalar fields in de Sitter space from the nonperturbative renormalization group

Understand

We investigate scalar field theories in de Sitter space by means of nonperturbative renormalization group techniques.

• We compute the functional flow equation for the effective potential of O(N) theories in the local potential approximation and we study the onset of curvature-induced effects as quantum fluctuations are progressively integrated out from subhorizon to superhorizon scales.
• This results in a dimensional reduction of the original action to an effective zero-dimensional Euclidean theory.
• We show that the latter is equivalent both to the late-time equilibrium state of the stochastic approach of Starobinsky and Yokoyama and to the effective theory for the zero mode on Euclidean de Sitter space.