COLLECTIVE STATES AND SYMMETRY REARRANGEMENT

Abstract

Collective states provide an important feature of the low-lying excitations in nuclei. Very often these states are inter-mingled with single particle excitations and surface vibrations of the finite nuclei. Here the authors wish to explore the collective states from the general viewpoint of symmetry rearrangement which has been studied extensively by Prof. Umezawa and his collaborators who showed, in a brilliant way, how the Goldstone bosons emerge and how they play the role in restoring the original symmetry operations. The authors have shown here an important relationship between the isovector collective states and symmetry rearrangement in nuclei. The interplay of strong and electromagnetic interactions leads to a finite energy gap for the isomagnons. The role of isomagnons in the low energy excitations has important consequences for {beta}-decay and it is anticipated in the excitation and decay of the matter in a heavy-ion collision. They have calculated the full response function of the Isobaric Analog State (IAS) at zero temperature and the finite temperature response function is analyzed at small T and long wavelength. The present approach of symmetry rearrangement and collective states has established a unified approach to the isovector collective states in nuclei and to collective states in allmore » many-particle systems. This was the conjecture of Hiroomi Umezawa when a study was initially started of symmetry rearrangement in nuclear systems in analogy to his previous studies in condensed matter systems. The authors believe that they have established, at least partially, the vision of Hiroomi Umezawa.« less