Authors

Citation

P. Ring et al., The time-dependent relativistic mean-field theory and the random phase approximation, NUCL PHYS A, 694(1-2), 2001, pp. 249-268

Citations number

38

Language

INGLESE

art.tipo

Article

Categorie Soggetti

Physics

Journal title

NUCLEAR PHYSICS A

ISSN journal

0375-9474
→ ACNP

Volume

694

Issue

1-2

Year of publication

2001

Pages

249 - 268

Database

ISI

SICI code

0375-9474(20011105)694:1-2<249:TTRMTA>2.0.ZU;2-O

Abstract

The Relativistic Random Phase Approximation (RRPA) is derived from the Time
-Dependent Relativistic Mean-Field (TD RMF) theory in the limit of small am
plitude oscillations. In the nosea approximation of the RMF theory, the RRP
A configuration space includes not only the usual particle-hole ph-states,
but also alphah-configurations, i.e. pairs formed from occupied states in t
he Fermi sea and empty negative-energy states in the Dirac sea. The contrib
ution of the negative-energy states to the RRPA matrices is examined in a s
chematic model, and the large effect of Dirac-sea states on isoscalar stren
gth distributions is illustrated for the giant monopole resonance in Sn-116
. It is shown that, because the matrix elements of the time-like component
of the vector-meson fields which couple the alphah-configurations with the
ph-configurations are strongly reduced with respect to the corresponding ma
trix elements of the isoscalar scalar meson field, the inclusion of states
with unperturbed energies more than 1.2 GeV below the Fermi energy has a pr
onounced effect on giant resonances with excitation energies in the MeV reg
ion. The influence of nuclear magnetism, i.e. the effect of the spatial com
ponents of the vector fields is examined, and the difference between the no
nrelativistic and relativistic RPA predictions for the nuclear matter compr
ession modulus is explained. (C) 2001 Elsevier Science B.V. All rights rese
rved.