Towards a unified description of the electroweak nuclear response

We briefly review the growing efforts to set up a unified framework for the description of neutrino interactions with atomic nuclei and nuclear matter, applicable in the broad kinematical region corresponding to neutrino energies ranging between few MeV and few GeV. The emerging picture suggests that the formalism of nuclear many-body theory (NMBT) can be exploited to obtain the neutrino-nucleus cross-sections needed for both the interpretation of oscillation signals and simulations of neutrino transport in compact stars.

A FAIR CHANCE FOR SUPERNOVAE

Nuclear physics plays an essential role in the dynamics of a type II supernova (a collapsing star). Recent advances in nuclear many-body theory allow now to calculate the stellar weak-interaction processes involving nuclei. The most important process is the electron capture on finite nuclei with mass numbers A > 55. This process is the source of neutrinos during the collapse phase. Neutrino-nucleus reactions play an interesting role during the collapse and the supernova nucleosynthesis.

55 YEARS OF THE SHELL MODEL: A CHALLENGE TO NUCLEAR MANY-BODY THEORY

Shell model calculations of nuclear energies and wave functions of nucleons outside closed shells interacting by effective two-body forces yield good agreement with much experimental data. Many attempts have been made to calculate nuclear energies ab initio, by starting from some form of an interaction between free nucleons. Recent results of such calculations claim to obtain reasonable agreement with measured energies. These results, however, are obtained for wave functions which are very complicated. It is difficult to see how such wave functions are consistent with independent nucleon motion, the very essence of the shell model. In some of those calculations, 3-body interactions play a very important role. This is puzzling since nuclear energies are accurately obtained in shell model calculations by using only effective two-body interactions. In this paper, some examples of simple shell model calculations are reviewed. They exhibit good agreement with experiment and the apparent absence of the need for effective 3-body interactions.

NUCLEAR MANY-BODY THEORY AT FINITE TEMPERATURE APPLIED TO A PROTONEUTRON STAR

We describe the structure of the Sommerfeld approximation to the Walecka model. The approximation is also applied to an extended version of the Boguta and Bodmer model which takes hyperon and lepton degrees of freedom into account, including trapped neutrinos. We apply the results to the protoneutron star problem.