Dispersion Relation of the Rho-Meson at Finite Temperature and Density
  The rho-meson mass shift, width broadening, and spectral density at finite temperature and nucleon density are estimated using a general formula which relates the self-energy to the real and imaginary parts of the forward scattering amplitude on the constituents of the medium. We saturate the scattering amplitude at low energies with resonances, while at high energies a Regge approach is taken in combination with vector meson dominance; experimental data is used wherever possible. The main result is that the rho-meson becomes increasingly broad with increasing nucleon density. The spectral density is suppressed in the resonance region 600 < M < 900 MeV and enhanced in the subresonance region M < 600 MeV. 
V. L. Eletsky and J. I. Kapusta