Temperature evolution of the nuclear shell structure and the dynamical nucleon effective mass

Abstract

We study the fermionic Matsubara Green functions in medium-mass nuclei at finite temperature. The single-fermion Dyson equation with the dynamical kernel of the particle-vibration-coupling (PVC) origin is formulated and solved in the basis of Dirac spinors, which minimize the grand canonical potential with the meson-nucleon covariant energy density functional. The PVC correlations beyond mean field are taken into account in the leading approximation for the energy-dependent selfenergy, and the full solution of the finite-temperature Dyson equation is obtained for the fermionic propagators. Within this approach, we investigate the fragmentation of the single-particle states and its evolution with temperature for the nuclear systems 56,68 Ni and 56 Fe relevant for the corecollapse supernova. The energy-dependent, or dynamical, nucleon effective mass is extracted from the PVC self-energy at various temperatures.

Impact of complex many-body correlations on electron capture in thermally excited nuclei around $^{78}$Ni

“…Moreover, the corresponding phase transition is quite sharp, in particular, at temperatures 0 ≤ T ≤ 0.5 MeV there is almost no change in the single-particle properties, as we have verified in Ref. [52]. Based on these observa- tions, we assume that in open-shell nuclei under consideration the GT + spectral functions do not change considerably in the temperature range 0 ≤ T ≤ 0.5 MeV.…”

“…The coefficient between T c and ∆(0) may vary from system to system in the relatively narrow limits, in particular, it was found in Ref. [52] that in 68 Ni it takes the value 0.7. We assume that in all isotopes under consideration superfluidity vanishes within 0.5 ≤ T ≤ 1 MeV interval.…”