Symmetries as Guidelines for Experiment - Example of Nuclear Geometrical Symmetries
 
Université de Strasbourg
Vendredi 04/02/2011, 11:00
Bat 703, p 45, CEA Saclay, Orme des Merisiers

Symmetry, one of the most classical subjects in physics, owes its importance to the fact that it governs conservation laws, transition probabilities and the unusual relations about observables, for instance level degeneracy. The possible experimental confirmation of theoretical predictions related to symmetry and thus validation of theories passes most often through comparison theory vs. experiment based on the energy levels and relative transition probabilities (branching ratios).

 

The nuclear systems are governed by saturating short range interactions leading to their compactness: the nucleons in the nucleus `touch each other' and the probability of finding them outside the nuclear surface decreases exponentially. This is also why the nuclear mean-field theories which simulate this type of behaviour are so naturally linked with `geometrical symmetries' - the symmetries of nuclear shapes.

 

And this is good so - geometrical symmetries are thought to be among the most intuitive and we do need (!?) group theory to discuss them with our colleagues-experimentalists - on whose help we count, of course.

 

The seminar will be focused on the general concepts of symmetry in nuclei addressing in particular the geometrical symmetries. And yet: Many of us have heard about the prolate, oblate and tri-axial nuclear ellipsoids... 10 times? 100 times ? more ? The seminar will not address again the same subject. I would like to use as a particular illustration the `fashionable' idea of the nuclear tetrahedral symmetry (pyramid-like shapes) but also others : Why attractive? Why potentially important? What arguments behind? How to combine the theory efforts with the experiments? We are also going to discuss the symmetry subject in the context of the exotic nuclei projects in France and in the world - and if time and audience permit: the new and quickly growing field of predictive power of nuclear theories.

Contact : aobertel

 

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