**Nuclear-reaction theory**

**Nuclear many-body theory and infinite matter**

The study of nuclear systems, from finite to infinite ones, requires the knowledge of the nuclear interaction and the choice of a many-body approach to solve the Schrödinger equation.

On one side, the nuclear interaction can be constructed as an effective interaction which is fit to reproduce the properties of either finite nuclei along the nuclear chart or even infinite matter, and the Schrödinger equation can usually be solved within the mean field approximation (Hartree-Fock). This approach goes under the name of energy-density functional theory.

On the other side, one can construct a realistic interaction which is instead fit to reproduce the nucleon-nucleon scattering data or even properties of few-body systems. In this latter case on then needs to solve the many-body problem via more sophisticated approximations beyond the mean field level, in order to build in the nuclear correlations. This defines the so called *ab initio* nuclear theory. The main difference between the two approaches is that the former is strongly model dependent, while the latter strives to be predictive.

At ECT* we are currently investigating the properties of infinite nuclear matter employing the *ab initio* self-consistent Green’s function approach (Arianna Carbone). This method is based on the use of the Green’s function to calculate both microscopic and bulk properties of the nuclear system. The use of interactions derived from chiral effective field theory gives us the possibility to be the more consistent as possible with the underlying quantum theory, QCD.

We are investigating both zero and finite-temperature properties of nuclear matter, with the objective of providing model independent nuclear physics input for the determination of the neutron star equation of state, to be used in astrophysical simulations of core-collapse supernovae and binary neutron star mergers.