Real time correlation functions and the functional renormalisation group

Understand

We put forward a functional renormalisation group approach for the direct computation of real time correlation functions, also applicable at finite temperature and density.

• We construct a general class of regulators that preserve the space-time symmetries, and allows the computation of correlation functions at complex frequencies.
• This includes both imaginary time and real time, and allows in particular the use of the plethora of imaginary time results for the computation of real time correlation functions.
• We also discuss real time computation on the Keldysh contour with general spatial momentum regulators.