Nuclear structure investigations in the future. J. Jolie, Universität zu Köln

How do complex systems emerge from simple ingredients Basic ingredients: two sets of indistinguishable fermions a complex short range force (Van der Waals typ) the possibility that one kind of fermions becomes the other kind + Binding energy 3fm The atomic nucleus forms a unique two-component mesoscopic system, which is hard to manipulate but genereous in the number of observables it emits.

Once the atomic nucleus is formed effective (in-medium) forces generate simple collective motions. shell structure Cooper pairing Quantum fluid

Comparison with another mesoscopic system Atomic nucleiQuantum dots Two componentsOne component Fixed number of particles Variable number of particles No thermal noise Thermal noise Difficult to manipulateEasy to manipulate Lots of observables Few observables 3-Dimensional1- or 2-Dimensional Fundamental entities

Chart of nuclear excitations. E exc J Energy (Temperature) Angular momentum (Deformation) In contrast to other mesoscopic systems the atomic nucleus can be excited and observed in a very clean way. Collective motion Quantal chaos Rotation induced effects Particle-hole excitations

Radioactive Ion Beams (RIBs) add a new axis to this chart. It will allow the manipulation of one important degree of freedom in atomic nuclei. E exc J N- Z N+Z Neutron-proton ratio Angular momentum (Deformation) Coupling with continuum Binding energy and also : dilute nuclear matter halos clustering new decay modes

Topic: Shell structure at largely asymmetric N, Z values In contrast to other physical systems the fact that one has a two-component system induces N and Z dependent shells. The shell structure will change drastically for strongly asymmetrical nuclei, due to changing spin-orbit interaction and coupling with continuum. Needed: New magic numbers need to be determined, farest reachable nuclei to be produced, mass measurements (traps, storage rings) transfer, knock-out and fragmentation reactions low-spin spectroscopy (B(E2), moments, E x ) Important for: Nuclear structure and astrophysics.

Topic: Pairing: bosonification of a fermionic system. Nuclei can be very well described as an interacting boson system due to the strong pairing between like nucleons. What is the role of the proton-neutron interaction and the other nucleons? Does a neutron and a proton form a paired state with T= 1 and T=0? Do the beautiful dynamical symmetries and even supersymmetries exist in presently unknown nuclei. Needed: Complete low-spin spectroscopy, Stable and unstable nuclei need to be produced in large quantities, Gamma spectroscopy and transfer reactions (beta Does there exist a even-even nuclei with a groundstate with ? Important for: Nuclear structure and all other kinds of mesoscopic physics.

Topic: quantum phase transitions at finite N, a new way to look at nuclear structure. Recently, a new nuclear shape phase diagram was introduced as well as new critical point symmetries. How do these phases evolve away from stability? What are the experimental signatures of such phase transitions and especially of up to now unknown new phases? Where do triaxial nuclei or nuclear molecules exist away from stability? Needed: Low-spin spectroscopy. Exotic nuclei need to be produced in sufficient quantities, Gamma, c-e spectroscopy and masses, Important for: Nuclear structure and mesoscopic physics with small N.

Topic: Quantal chaos versus integrable many-body systems The atomic nucleus forms an unique laboratory to study chaos in a quantal system due to the abibility to determine a complete set of excited states. The interacting boson model and the shell model are ideal realistic models to study this subject. Moreover it provides examples of nuclei that do allow the experimental determination of the characteristic observables. Needed: Complete spectroscopy at all possible spins. Exotic and stable nuclei need to be produced in large quantities, gamma spectroscopy and transfer reactions, Important for: Nuclear structure and Quantum Mechanics

Challenge: Low spin physicists need high-spin techniques and high spin physicists need low-spin methods and theoreticians. First tries are RISING and MINIBALL. It works! The I and J community can merge.

Challenge: The target is the beam, so we have to develop new instruments. Miniball Phase 1 Data from REX-ISOLDE

Advanced Gamma-Ray Tracking array (AGATA)

Challenge: We need a sufficient number of RIB and stable beam facilities. RIB: Experiments with few data: frontier physics. Experiments with more data: highlighting physical mechanism. Many questions have to be solved: GANIL GSI REX-ISOLDE MAFF EURISOL, RIA, RIKEN, etc. +STABLE BEAMS all are needed! Experiments at stable beam facilities with very high sensitivity. Answering new questions (feedback).

Challenge: While the next generation of experimental facilities is in construction and the field is booming with new ideas, the universities are still reducing the number of faculty positions. There is an urgent need for: large scale nuclear shell model, mean field and many-body theorists, conserted action to reinforce the university based research, good and hands-on education at stable beam facilities. Notice: without a strong university support, no students. Positive note: Public relation has improved tremendeously. Several young full professors were appointed on experimental chairs. Also Atomic Physics revived with the advent of storage rings and synchrotron radiation.

Conclusion Nuclear physics is moving quickly, especially due to the development of: New detectors X(5) 152 Sm New concepts The future looks bright, but much work has to be done! New facilities