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Symétries nucléaires à faible isospin

Abstract : With the development of radioactive beams, an area of intense research in nuclear physics concerns the structure of exotic systems with roughly equal numbers of protons and neutrons. These nuclei might in fact develop a proton-neutron superfluidity whose importance compared to pairing correlations between like nucleons is currently investigated. The work presented in this thesis suggests to look at such a competition in an algebraic framework based on a Wigner SU(4) symmetry that combines the pseudo-spin and isospin degrees of freedom. After a detailed review of group theory in quantum mechanics, the validity of the pseudo-SU(4) classification is shown via a direct analysis of realistic shell model states. Its consequences on binding energies and β decay are also studied. Moreover, a simplified boson realisation with zero orbital angular momentum is used to find some physical features of N=Z nuclei such as the condensation of α-like structures or the destruction of isoscalar superfluid correlations by the spin-orbit potential. Finally, another bosonization scheme that includes quadrupole degrees of freedom (IBM-4 model) is tested for the first time by diagonalization of a full Hamiltonian deduced from a realistic shell model interaction. The quality of the results, especially for odd-odd nuclei, allows one to consider this boson approximation as an alternative to standard fermionic approaches for the collective structure of the exotic line N∼Z=28-50.
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Contributor : Michel Lion Connect in order to contact the contributor
Submitted on : Thursday, October 6, 2016 - 2:21:21 PM
Last modification on : Tuesday, February 19, 2019 - 10:04:10 AM
Long-term archiving on: : Saturday, January 7, 2017 - 1:47:50 PM


  • HAL Id : in2p3-00008665, version 1



O. Juillet. Symétries nucléaires à faible isospin. Physique Nucléaire Théorique [nucl-th]. Université de Caen, 1999. Français. ⟨in2p3-00008665⟩



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