Spectral change of sigma and omega mesons in a dense nuclear medium
  The spectra of the scalar ($\sigma$) and vector ($\omega$) mesons in nuclear matter are studied in detail using the quark-meson coupling (QMC) model. It is shown that above normal nuclear matter density the effects of $\sigma$-$\omega$ mixing and the decay of the $\sigma$ into $2\pi$ change the spectra of $\sigma$ and $\omega$ mesons considerably. As in Quantum Hadrodynamics we find a remarkable spectral change in the $\sigma$ meson and the longitudinal mode of the $\omega$ meson, namely a two-peak structure. 
K. Saito, K. Tsushima and A.W. Thomas