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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]

Applying TQRPA calculations of Gamow–Teller strength functions in hot nuclei, we compute the (anti)neutrino spectra and energy loss rates arising from weak processes on hot 56Fe under pre-supernova conditions. We use a realistic pre-supernova model calculated by the stellar evolution code MESA. Taking into account both charged and neutral current processes, we demonstrate that weak reactions with hot nuclei can produce high-energy (anti)neutrinos. We also show that, for hot nuclei, the energy loss via (anti)neutrino emission is significantly larger than that for nuclei in their ground state. It is found that the neutral current de-excitation via the νν¯-pair emission is presumably a dominant source of antineutrinos. In accordance with other studies, we confirm that the so-called single-state approximation for neutrino spectra might fail under certain pre-supernova conditions.

Applying TQRPA calculations of Gamow–Teller strength functions in hot nuclei, we compute the (anti)neutrino spectra and energy loss rates arising from weak processes on hot 56 Fe under pre-supernova conditions. We use a realistic pre-supernova model calculated by the stellar evolution code MESA. Taking into account both charged and neutral current processes, we demonstrate that weak reactions with hot nuclei can produce high-energy (anti)neutrinos. We also show that, for hot nuclei, the energy loss via (anti)neutrino emission is significantly larger than that for nuclei in their ground state. It is found that the neutral current de-excitation via the ν ν ¯ -pair emission is presumably a dominant source of antineutrinos. In accordance with other studies, we confirm that the so-called single-state approximation for neutrino spectra might fail under certain pre-supernova conditions. [ABSTRACT FROM AUTHOR]

Abstract This review article takes stock of the progress made in understanding the phase transition in hot nuclei and highlights the coherence of observed signatures. [ABSTRACT FROM AUTHOR]

High energy gamma-rays from the 116 Sn + 24 Mg reaction at 23 A MeV were measured using the MEDEA detector at LNS – INFN Catania. Combining this new data with previous measurements yields a detailed view of the quenching of the Giant Dipole Resonance as a function of excitation energy in nuclei of mass A in the range 120 ÷ 132 . The transition towards the disappearance of the dipole strength, which occurs around 230 MeV excitation energy, appears to be remarkably sharp. Current phenomenological models give qualitative explanations for the quenching but cannot reproduce its detailed features. [ABSTRACT FROM AUTHOR]

The study of properties of nuclei under extreme conditions of temperature and density has been the subject of many investigations in recent decades, since they are very important in the study of the process of supernovae, neutron stars and nuclei. Heavy-ion collision experiments are often employed to determine these properties. We present a short and limited review of the theoretical and experimental status of determining the temperature and density of the disassembling hot nucleus from ratios of the yields of emitted fragments.

Level density parameters of 208Pb and 91Zr in equilibrium states have been calculated with a new fugacity approximation namely a thermal wavelength approximation. In this approximation, the fugacity is directly proportional to the nucleon density. In contrast with the constant fugacity, the thermal wavelength approximation gives a simpler way to calculate the nuclei constant radius and the density profile. The calculated 208Pb nuclear density is about 0.17 (fm-3) in which the discrepancy is 0.1% higher than the experimental one. The level density parameters are 14% higher than the experimental results due to neglecting of the shell correction.

A universal decay law (UDL) for light cluster decay of excited nuclei is formulated by fitting the UDL half-lives to those evaluated within an excitation energy-dependent double folding model (DFM). The half-lives are evaluated within a preformed cluster model. The excitation energy dependence is introduced both in the energy of the emitted cluster and in the interaction potential through the density distributions of the interacting nuclei. The half-lives are found to decrease when the difference between the excitation energies of the parent and daughter nuclei, Δ E ⁎ > 0, increases, with the reduction being a few orders of magnitude for higher values of Δ E ⁎. This can be of importance for nucleosynthesis calculations of heavy elements formed in extremely hot environments, as well as in highly energetic heavy-ion collisions. The UDL for excited nuclei is used to provide an estimate of the enhancement in the cluster decay rates of thermally excited nuclei such as those produced in r-process nucleosynthesis. [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]

After a brief review of the history of viscosity from classical to quantal fluids, a discussion of how the shear viscosity η of a finite hot nucleus is calculated directly from the width and energy of the giant dipole resonance (GDR) of the nucleus is given in this paper. The ratio η/ s with s being the entropy volume density, is extracted from the experimental systematic of GDR in copper, tin and lead isotopes at finite temperature T. These empirical results are compared with the results predicted by several independent models, as well as with almost model-independent estimations. Based on these results, it is concluded that the ratio η/ s in medium and heavy nuclei decreases with increasing T to reach $(1.3 - 4) \times \hbar /(4\pi k_{\mathrm {B}})$ at T = 5 MeV, which is almost the same as that obtained for quark-gluon plasma at T > 170 MeV. [ABSTRACT FROM AUTHOR]