Department of Physics

Objectives

The FIDIPRO project is focused on advanced studies in theoretical nuclear structure aiming at description of global properties of nuclei.

The search for universal description of nuclear properties in nuclei far from stability is the main theme and goal of the present project. We will focus on systematic features of ground and low-lying excited states that differentiate between well- and weakly-bound nuclear systems.

Finding the best energy density functionals, including dynamical effects and symmetry restoration, will be one of the principal thrusts of the present project. By employing various criteria (agreement with measured masses, low-lying excited states, giant vibrations, and rotational properties) our goal is to find optimal parametrization of the functional. By finding correlations between parameters, we hope to reduce their number and to understand physical reasons why different parametrizations yield similar results. On the other hand, we also want to expand the parametrizations to cover aspects dictated by physics arguments and/or motivations coming from the effective field theory and QCD.

We are convinced that the present stage of theory requires constructing new energy density functionals supplemented by a complete error and covariance analysis. We believe that it is not sufficient to "predict" properties of exotic nuclei by extrapolating properties of those measured in experiment. We must also quantitatively determine errors related to such an extrapolation. Moreover, for an experimental work it is essential that an improvement gained by measuring one or two more isotopes be quantitatively known. From theoretical perspective, we must also know the confidence level with which the parameters of the functional are determined. Analyses of this type constitute a standard approach in other domains of physics, but they are seldom up to now performed in theoretical nuclear structure research.

We intend to extend the energy density functionals by enriching the density dependence of the isoscalar and isovector coupling constants, both in the particle-hole and particle-particle channels. This will require studies of new functionals when applied to infinite or semi-infinite nuclear matter. Moreover, in the particle-particle channel we plan to extend the functional by adding kinetic terms. In the particle-hole channel, on the other hand, we want to enrich the density dependence of the effective mass in order to differentiate between its value in the bulk and at the Fermi surface.

One of our goals is to find a new strategy of looking for new energy density functionals in time-odd channels by an analysis of high angular momentum states. Study of the so-called terminating states seems to be especially promising, mostly due to their extremely simple single-particle structure. Indeed, these states could constitute an invaluable (and up to now only scarcely used) source of information about the underlying mean field. Within the same scope, we intend to study single-particle polarization effects in rotating system, and the angular momentum alignment effects.

The universal energy density functionals will also be used for a description of low-lying excited states. This will require going beyond static approximation and studying vibrational states, mostly within the RPA and QRPA methods. In weakly-bound nuclei, such analyses must be accompanied by proper treatment of the particle continuum and open channels.

This research programme on exotic nuclei will be augmented by building a consistent system of theoretical tools that are required for the research activity in this domain of physics. This will primarily include a collection of computer codes, expertise to use them, manuals and user guides, and a repository of computed results. Theoretical methods used at present in the nuclear structure theory require an effort of many year-person investment to build and test very advanced computer codes.

Teams collaborating with the leader of the FIDIPRO project have already published several such codes. However, the domain definitely suffers from a lack of concerted effort in this direction, whereupon some activities are duplicated and some wasted. We will lead and supervise construction of the WEB-based consistent and open system of codes available to all researchers, thus providing a qualitative boost in the field.