Resummation of infrared logarithms in de Sitter space via Dyson-Schwinger equations: the ladder-rainbow approximation

Understand

We study the infrared (large separation) behavior of a massless minimally coupled scalar quantum field theory with a quartic self interaction in de Sitter spacetime.

• We show that the perturbation series in the interaction strength is singular and secular, i.e.
• it does not lead to a uniform approximation of the solution in the infrared region.
• Only a nonperturbative resummation can capture the correct infrared behavior.