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Accurate estimates of (anti)neutrino spectra and luminosities are needed to determine the possibility of pre-supernova neutrino detection. Using the recently proposed thermal quasiparticle random-phase approximation (TQRPA) method, we have studied thermal effects on the spectra and luminosities of (anti)neutrinos emitted in nuclear weak-interaction processes under pre-supernova conditions. We show that a thermodynamically consistent consideration of Gamow–Teller transitions in hot nuclei increases the energy luminosity and results in larger average (anti)neutrino energies. [ABSTRACT FROM AUTHOR]

The pairing phase transition is investigated in hot even-even and even-odd Pd isotopes such as 106 ≤ A ≤ 108 in a framework of a microscopic approach that takes into account the statistical fluctuations. In this aim, one considers the Modified BCS method (MBCS). The latter is extended to the odd system case, where the blocking effect is included. The model was applied to the evaluation of the thermal properties such as the excitation energy, entropy and heat capacity. The obtained results are compared on one hand to the usual finite temperature BCS (FTBCS) method and on the other hand to the experimental data. The obtained results allow to show that the thermal fluctuations smooth out the superfluid-normal (SN) phase transition observed in the usual FTBCS results. Moreover, in the region where the pairing phase transition occurs, the experimental data of thermal properties are better reproduced when statistical fluctuations are considered in MBCS method instead of the FTBCS approach. [ABSTRACT FROM AUTHOR]

The thermal properties of Tin isotopes such as 68≤N≤78, are studied. The calculations are performed by means of the modified Lipkin-Nogami (MLN) approach that takes into account the thermal and quantal fluctuations. The obtained results are compared to the conventional finite-temperature Bardeen-Cooper-Schrieffer (FTBCS) approach and to the modified Bardeen-Cooper-Schrieffer (MBCS) method. The numerical results illustrate the effect of the statistical and quantal fluctuations on the description of the phenomenon of pairing phase transition. [ABSTRACT FROM AUTHOR]

The S-shaped heat capacity, which has recently been claimed to be a fingerprint of the superfluid-to-normal phase transition in nuclei, is studied in the case of 166 element. The calculations are performed by means of the modified Bardeen-Cooper-Schrieffer (MBCS) approach that takes into account the thermal fluctuation. The obtained results are compared to the experimental data and to the FT-BCS theoretical predictions. The present study illustrates the effect of the fluctuations of the quasiparticle (QP) number on the heat capacity. [ABSTRACT FROM AUTHOR]

The approach in a theory of collective excitations in hot nuclei exploring the formalism of thermo field dynamics and the model Hamiltonian consisting of a mean field, the BCS paring interaction, and long-range particle–hole effective forces is reexamined. In contrast with earlier studies, it is found that a wave function of a thermal phonon is depended not only on the Fermi–Dirac thermal occupation numbers of the Bogoliubov quasiparticles consisting the phonon but also on the Bose thermal occupation numbers of the phonon. This strongly affects a thermal phonon coupling due to the renormalization of a phonon–phonon interaction and enlarging the number of thermal two-phonon configurations coupled with one-phonon ones. Moreover, it is shown that the formulation of the double tilde conjugation rule for fermions proposed by I. Ojima is more appropriate in the context of the present study than the original one by H. Umezawa and co-workers. [ABSTRACT FROM AUTHOR]