Symmetry Rearrangement of Spin and Isospin Symmetries and the Collective Modes in Nuclear Matter

✍ Scribed by Hanxin He; F.C. Khanna; H. Umezawa

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 564 KB
• Volume: 256
• Category: Article
• ISSN: 0003-4916
• DOI: 10.1006/aphy.1997.5675

✦ Synopsis

A consistent theory of the spin and isospin excitations in an infinite nuclear system is formulated based on the Ward Takahashi (W T) relations among various many point Green's functions, which are derived from the requirement of the rotational invariance in spin and isospin space, SU(4). Collective modes are found to be six Nambu Goldstone bosons, called spin, isospin, and spin isospin waves, which appear as a result of the symmetry rearrangement of the SU(4) symmetry. The W T relations are used to determine correlations among collective modes and to obtain a consistent expression for the static susceptibility beyond the random phase approximation. A consistent picture of the isovector collective excitations and their relationship to numerous experimental results is established. A partially conserved isovector current, analogous to a partially conserved axial current, in the symmetry rearrangement of isospin symmetry is established. This helps to define non-pertubatively the finite energy shift due to the explicit symmetry breaking terms. 1997 Academic Press I. INTRODUCTION Investigation of spin and isospin excitations in nuclei has attracted a great deal of attention recently [1]. Such excitations are present in all nuclei and this universal characteristic makes them highly interesting. It is quite likely that an underlying article no. PH975675 144 0003-4916Â97 25.00