Spectral functions from the functional renormalization group at finite   temperature and density
  We present a viable method to obtain real-time quantities such as spectral functions or transport coefficients at finite temperature and density within a non-perturbative Functional Renormalization Group approach. Our method is based on a thermodynamically consistent truncation of the flow equations for 2-point functions with analytically continued frequency components in the originally Euclidean external momenta. We demonstrate its feasibility by calculating the mesonic spectral functions in the quark-meson model at different temperatures and quark chemical potentials, in particular around the critical endpoint in the phase diagram of the model. 
Ralf-Arno Tripolt, Nils Strodthoff, Lorenz von Smekal and Jochen   Wambach
hep-ph hep-th nucl-th