Relativistic nuclear field theory and application to the spin-isospin response of nuclei

Abstract:  Atomic nuclei are complex systems where single-nucleon and collective degrees of freedom are deeply intertwined. The nuclear structure method which I will present describes the nucleus as a system of relativistic nucleons interacting via effective meson-exchange, and applies nuclear field theory in order to account for nucleonic correlations. In this way, this approach naturally connects the intermediate-energy scales of mesons to the low-energy domain of nucleons and their collective motion, and provides a consistent framework for the description of ground and excited states in a wide range of nuclei. Recently, we have extended this formalism to the description of isospin-transfer modes in open-shell nuclei [1], which have various applications in nuclear and particle physics as well as astrophysics. In the charge-exchange channel, the coupling between single nucleons and collective vibrations generates a time-dependent proton-neutron effective interaction, in addition to the static pion and rho-meson exchange, and induces fragmentation and spreading of the transition strength. Such effects are important to reproduce weak interaction rates and to tackle the quenching problem of the Gamow-Teller strength. I will show recent results of calculations for spin-isospin excitations and weak decays in nuclei, and will address further developments. [1] C. Robin and E. Litvinova, Eur. Phys. J. A, 52 (2016).