In-Medium Spectral Functions of Vector- and Axial-Vector Mesons from the   Functional Renormalization Group
  In this work we present first results on vector and axial-vector meson spectral functions as obtained by applying the non-perturbative functional renormalization group approach to an effective low-energy theory motivated by the gauged linear sigma model. By using a recently proposed analytic continuation method, we study the in-medium behavior of the spectral functions of the $\rho$ and $a_1$ mesons in different regimes of the phase diagram. In particular, we demonstrate explicitly how these spectral functions degenerate at high temperatures as well as at large chemical potentials, as a consequence of the restoration of chiral symmetry. In addition, we also compute the momentum dependence of the $\rho$ and $a_1$ spectral functions and discuss the various time-like and space-like processes that can occur. 
Christopher Jung, Fabian Rennecke, Ralf-Arno Tripolt, Lorenz von   Smekal, Jochen Wambach
hep-ph