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$ρ$ - meson spectral function in hot nuclear matter

We study the $ρ$-meson spectral function in hot nuclear matter by taking into account the isospin-symmetric pion and the nucleon loops within the quantum hadrodynamics (QHD) model as well as using an effective chiral SU(3) model. The spectral function of the $ρ$ meson is studied in the mean field approximation (MFA) as well as in the relativistic Hartree (RHA) approximation. The inclusion of the nucleon loop considerably changes the $ρ$-meson spectral function. Due to a larger mass drop of $ ρ$ meson in the RHA, it is seen that the spectral function shifts towards the low invariant mass region, whereas in the MFA the spectral function is seen to be slightly shifted towards the high mass region. Moreover, while the spectral function is observed to be sharper with the nucleon-antinucleon polarization in RHA, the spectral function is seen to be broader in the MFA.