  We propose a new approach to compute correlators of quantum fields in de
Sitter space. It is based on nonequilibrium field theory techniques, and
exploits de Sitter symmetries so as to partially reduce the number of
independent variables of n-point functions in a manner that preserves the
usefulness of a momentum representation, e.g., for writing spatial convolution
integrals as simple products. In this representation, the two-point function of
a scalar field only depends on two physical momenta, and the corresponding
Schwinger-Dyson evolution equations take the form of momentum flow equations.
Moreover, standard diagrammatic rules can be entirely formulated in this
representation. The method is suitable for analytical approximations as well as
numerical implementations. In forthcoming publications, we apply it to resum
infrared logarithmic terms appearing in the perturbative calculation of vertex
and correlation functions.
