Dispersion relation of the $\rho$ meson in hot/dense nuclear matter
  The dispersion relation of $\rho$ meson in both timelike and spacelike regimes in hot and dense nuclear medium is analyzed and compared with $\sigma $ meson based on the quantum hadrodynamics model. The pole and screening masses of $\rho $ and $\sigma$ are discussed. The behavior of screening mass of $\rho$ is different from that of $\sigma$ due to different Dirac- and Fermi-sea contributions at finite temperature and density. 
Ji-Sheng Chen, Jia-Rong Li, Peng-Fei Zhuang