Cosmological functional renormalisation group, extended Galilean
  invariance and the sweeping effect
  The functional renormalisation group is employed to study the non-linear
regime of late-time cosmic structure formation. This framework naturally allows
for non-perturbative approximation schemes, usually guided by underlying
symmetries or a truncation of the theory space. An extended symmetry that is
related to Galilean invariance is studied and corresponding Ward identities are
derived. These are used to obtain (formally) closed renormalisation group flow
equations for two-point correlation functions in the limit of large wave
numbers (small scales). The flow equations are analytically solved in an
approximation that is connected to the 'sweeping effect' previously described
in the context of fluid turbulence.
