ИСТИНА

Microscopic nuclear structure calculations based on realistic models of the nucleon- nucleon (NN) interaction, i.e. NN interactions which are adjusted to reproduce the experimental data of NN scattering, fail to reproduce the saturation properties of nuclear matter as well as bulk properties of nuclei like their binding energies and radii of charge distribution. Therefore it has become popular to supplement these approaches by a more or less phenomenological model for a 3-N force, adjust its parameters to the saturation of infinite nuclear matter and proceed to other nuclear structure studies. Within this project we intend to explore a variety of possible sources for a 3-N force, including e.g. effects of sub-nucleonic degrees of freedom like excitations of the interacting nucleons or the quark structure of nucleons, relativistic effects as considered in the Dirac-Brueckner approach, 3-N forces emerging in a chiral effective field theory but also the effective 3-N forces originating from the renormalisation to a restricted model space for the nucleonic degrees of freedom. For that purpose we plan to develop a technique which allows a consistent treatment of 3-N forces and 3-N correlations. It is the aim of the project to explore similarities and differences between these various many-nucleon forces or density-dependent NN forces in a systematic way and investigate their possible contributions to describe the saturation of nuclear matter as well as the bulk properties of finite nuclei.

The aim of this project is to explore various sources for a 3-N force, including e.g. effects of sub-nucleonic degrees of freedom like excitations of the interacting nucleons or the quark the quark structure of nucleons, relativistic effects as considered in the Dirac-Brueckner approach, 3-N forces emerging in a chiral effective field theory but also the effective 3-N forces originating from the renormalisation to a restricted model space for the nucleonic degrees of freedom. The projection techniques of the effective operator method will be used to determine the corresponding effective interactions to be used in mean-field calculations of the many-body system. It will be studied to which extent these effective NN and many-nucleon forces may explain the empirical density-dependent NN interaction, which is required as a supplement of realistic NN interactions in order to provide a good description of the saturation property of infinite nuclear matter as well as the bulk properties of finite nuclei. Special attention will be paid to the role of rearrangement terms in nuclear matter as well as finite nuclei. In particular, we will consider 3-N forces, which are needed to explain the experimental data of few nucleon systems, and study how these forces evolve in nuclear many-body systems. For that purpose we will try to import the technique developed by the Moscow group for the solution of the Faddeev equations to the solution of corresponding Bethe-Faddeev equations in infinite nuclear matter. The matrix formulation will allow to determine effective 2-N and 3-N forces for the regime of low-momentum components in the wave function, which can then be used in effective mean field calculations.