Nuclear shell structure in a finite-temperature relativistic framework

The shell evolution of neutron-rich nuclei with temperature is studied in a beyond-mean-field framework rooted in the meson-nucleon Lagrangian. The temperature-dependent Dyson equation with a dynamical kernel taking into account the particle-vibration coupling (PVC) is solved for the fermionic propagators in the basis of the thermal relativistic mean-field Dirac spinors. The calculations are performed for 68-78Ni in a broad range of temperatures 0 T 4 MeV. Special focus is put on the fragmentation pattern of the single-particle states, which is further investigated within toy models in truncated model spaces. Such models allow for quantifying the sensitivity of the fragmentation to the phonon frequencies, the PVC strength, and the mean-field level density. This study provides insights into the temperature evolution of the PVC mechanism in real nuclear systems under the conditions which occur in astrophysical environments. In this connection, we discuss the temperaturedependent nucleon effective mass and symmetry energy coefficient, which are key ingredients of the nuclear equation of state.