Theories of nuclear structure
Document Actions
The nuclear many-body problem is a complicated one. The ab-initio approaches that attempt to solve it exactly using the bare nucleon-nucleon interaction are limited to either infinite nuclear matter or very small systems up to 16O. As a consequence, effective methods will remain the tools of choice for most of the chart of nuclei. Among the promising ones to obtain a global description throughout the chart of nuclei are those based on self-consistent mean-field approaches using effective interactions like the ones that I am using. In comparison to other models applied to heavy nuclei these methods have the advantage that they use universal effective interactions that, in principle, can be extrapolated to exotic nuclei as those that will become available at SPIRAL2 without the need to locally adjust parameters. However, there is not yet a unique effective interaction, so the available ones have a limited predictive power when extrapolated very far from the regions they were fitted to. This is where the ab-initio methods can give us guidance on the structural form of the effective interaction and constraints on the effective coupling constants.
My current work is three-fold. First, I add correlations to the mean-field via projection and configuration mixing. For most nuclei, the most important correlations to be added to the mean field are related to particle-number and angular momentum projection, and to the mixing of states with different shape. The existing numerical implementations still make restrictive assumptions about the symmetries of the mean-field states and limit the degrees of freedom for the configuration mixing to a single one. The codes I currently develop will release many of the remaining symmetries and allow for more than one generator coordinate for the configuration mixing. The second part of my work is to develop and test effective interactions for such calculations. The third part, of course, is the interaction with the experimentalists who are interested in results obtained with the existing theoretical tools.
Among the applications of the beyond-mean-field method I am developing were the analysis of shape coexistence in the neutron-deficient Kr and Pb regions, or the influence of angular-momentum projection on the fission barrier of actinide nuclei. We are now capable to calculate the beyond-mean-field ground-state correlations on a large scale for several hundred even-even nuclei. But also pure mean-field calculations still give useful results for many nuclei and observables, a recent project was the description of quasi-particle states and rotational bands in the transfermium region.
About the future, one of the interesting things for me will be to understand the structural changes when going from stable nuclei to exotic ones. I do not think that the theoretical tools that I use have to be particularly changed to describe exotic systems, perhaps with the exception for those very close to the drip-line, which gives me good confidence that we will be able to analyse many of the new features in very exotic systems without having to anticipate their exact nature. However, we still have many problems to describe the detailed structure of stable and near-stable systems, and the collaboration I am involved in will use the years before SPIRAL2 comes up to resolve them. I have a good hope that we will have the suitable theoretical tools available at the time SPIRAL2 delivers first results.
More info:
Michaël Bender's talk
Nuclear theories session
Words collected by K. Turzó at the XVe Colloque GANIL, Giens, France, from May 29th to June 2nd, 2006.
My current work is three-fold. First, I add correlations to the mean-field via projection and configuration mixing. For most nuclei, the most important correlations to be added to the mean field are related to particle-number and angular momentum projection, and to the mixing of states with different shape. The existing numerical implementations still make restrictive assumptions about the symmetries of the mean-field states and limit the degrees of freedom for the configuration mixing to a single one. The codes I currently develop will release many of the remaining symmetries and allow for more than one generator coordinate for the configuration mixing. The second part of my work is to develop and test effective interactions for such calculations. The third part, of course, is the interaction with the experimentalists who are interested in results obtained with the existing theoretical tools.
Among the applications of the beyond-mean-field method I am developing were the analysis of shape coexistence in the neutron-deficient Kr and Pb regions, or the influence of angular-momentum projection on the fission barrier of actinide nuclei. We are now capable to calculate the beyond-mean-field ground-state correlations on a large scale for several hundred even-even nuclei. But also pure mean-field calculations still give useful results for many nuclei and observables, a recent project was the description of quasi-particle states and rotational bands in the transfermium region.
About the future, one of the interesting things for me will be to understand the structural changes when going from stable nuclei to exotic ones. I do not think that the theoretical tools that I use have to be particularly changed to describe exotic systems, perhaps with the exception for those very close to the drip-line, which gives me good confidence that we will be able to analyse many of the new features in very exotic systems without having to anticipate their exact nature. However, we still have many problems to describe the detailed structure of stable and near-stable systems, and the collaboration I am involved in will use the years before SPIRAL2 comes up to resolve them. I have a good hope that we will have the suitable theoretical tools available at the time SPIRAL2 delivers first results.
More info:
Michaël Bender's talk
Nuclear theories session
Words collected by K. Turzó at the XVe Colloque GANIL, Giens, France, from May 29th to June 2nd, 2006.
