The single-particle interaction in nuclear matter via the relativistic Dirac-Brueckner approach (original) (raw)

Relat1vistic nuclear matter calculations and the deficiency of one-boson exchange potentials

Nuclear Physics A, 1972

Nuclear matter properties are calculated using the Schierholz and Thompson-Gersten-Green relativistic potentials. The Brueckner equations for nuclear matter are modified to incorporate corresponding relativistic kinematics. It is found that both relativistic and nonrelativistic one-boson exchange potentials yield overbinding and collapse of nuclear matter. By comparing our relativistic results and earlier non-relativistic results. it is shown that the main deficiency of OBE models is not the use of a non-relativistic limit but is rather the lack of a strong intermediate-and short-range tensor force. The proper treatment of 2~ exchange might yield the requisite strong tensor force.

Dirac phenomenology and nuclear single-particle states

Nuclear Physics, 1995

This paper is concerned with the application of a relativistic shell model to the study of nuclear single-particle states. This relativistic model is applied to medium and heavy nuclei and shown to reproduce satisfactorily the single-particle energies and the rms radii. Energy-independent potentials give a reasonable account of the experimental binding energies, but the empirical analysis of the energy dependence of the potentials reveals a Fermi-surface anomaly. The parameters of the model are also analysed and found to vary systematically with both energy and mass number. The relativistic model is then reformulated in terms of folded-model potentials. The single-particle spectrum and charge rms radius of 4°Ca are reasonably reproduced, with an energy-and density-independent nucleon-nucleon force, and their sensitivity to the model parameters is studied.

A relativistic one-boson-exchange model of nucleon-nucleon interaction

Nuclear Physics B, 1972

A relativistic one-boson-exchange model due to the exchange of the ~r, r/, e, p and to mesons and an effective o is presented for the elastic nucleon-nucleon (NN) interaction. The model is based on relativistic quantum mechanics as formulated by Foldy, Fong and Sucher, Coester and others. The potential is calculated from the off-shell field theoretical Born terms corresponding to the forementioned mesons. In order to avoid divergences form factors are introduced. For the vector-meson exchanges they are assumed to have Regge asymptotic behaviour. The fictitious o is fitted to the uncorrelated n~r S-wave contrl"bution calculated by Durso which is to a great extent given by diagrams with an intermediate isobar. The remaining coupling constants are adjusted tt~ the NN phase shifts and to the binding energy of the deuteron. The model fits the phase shifts fairly well and accounts for the deuteron parameters. The obtained coupling constants are compared to the values found by other investigations. * By this we mean multimeson exchange contributions.

Relativistic interactions between nuclei

Physical Review D, 1977

A relativistic theory of the inclusive scattering of nuclei is given. The theory is applicable to meson production reactions as well as to the yields of light nuclei. A characterization of the relativistic nuclear wave function is given and its connection to the standard wave function is explicitly shown. Counting rules are derived that allow one to simply characterize the behavior of the reaction cross sections in terms of the short range behavior of the nucleon-nucleon force. Good agreement with experiment is achieved if the force is assumed to be due to the exchange of vector mesons with monopole form factors at each vertex. The predictions are successfully compared to several reactions.

On the momentum dependence of the nucleon-nucleus optical potential

Nuclear Physics A, 1994

The momentum dependence of the mean-field contribution to the real part of the optical model potential is investigated employing realistic nucleon-nucleon interactions. Within a non-relativistic approach a momentum dependence originates from the non-locality of the Fock exchange term. Deducing the real part of the optical model from a relativistic Dirac Brueckner Hartree Fock approximation for the self-energy of the nucleons yields an additional momentum dependence originating from the non-relativistic reduction of the self-energy. It is demonstrated that large Fock terms are required in the non-relativistic approach to simulate these relativistic features. A comparison is made between a local density approximation for the optical model and a direct evaluation in finite nuclei.

Nuclear interactions in few-body systems

Czechoslovak Journal of Physics, 1989

Topics of nuclear interactions and meson-exchange currents in few-body systems are reviewed. The status of the effective nuclear theory is briefly examined and the impact of current research on the resolution ofopen problems is discussed. I. INTRODUCTION Recent theoretical nuclear investigations with few-body systems can be grouped into three categories. First, those which aim to render more complete the traditional effective theory of the nuclear medium based on non-relativistic meson-exchange phenomena with elementary nucleons and mesons. Second, those which attempt to take into accourir the compound nature of nucleons and mesons by means of microscopic QCD-inspired models for the structure and the interactions among these particles. Finally, those which look at novel testing grounds for nuclear theoretical ideas, anticipating the advent of new experimental facilities and proposing novel experimental tests. The first category includes, among other things, the continuing effort to improve the boson-exchange models (OBE) of the NN interaction, the introduction of relativistic aspects in the two-nucleon and multi-nucleon theory, and the incorporation of meson-exchange currents (MEC) in all photoreactions and weak interaction processes. The second group of investigations spans the work on constituent quark models, bag and solution models of nucleons and mesons, and the search for convincing signais of such structures in short-range correlations in nuclear systems and in electroand photo-reactions. Prominent among the investigations in the third category is research into spin observables in scattering of polarized projectiles from polarized or unpolarized targets, analysis of data from double and triple coincidence experiments, leading to enhanced sensitivity to the underlying dynamics, systematic experimental studies of excited baryons, and searches for dibaryons. lin the following, we will summarize the current status of relevant theoretical constructs in these areas of research related to the work that was contributed to this conference, and we will review these contributions to discover how they help to resolve open problems in nuclear physics.

Towards a relativistic self-consistent nucleon spectral function in the nuclear medium

Physics Letters B, 1993

An iterative procedure is developed for solving the Schwinger-Dyson equation for the coupled nucleon and pion propagators for the case when vertex corrections are neglected. The presence of ghost poles in the dressed propagators is avoided by using explicitly only the imaginary part of the propagators, eliminating the real part through a dispersion relation.

The nucleon-nucleon interaction and the nuclear many-body problem

Physics Reports, 1985

We shall leave the proof ofconfinement to particle physicists; forour purposes, the fact that we don't seequarks is strong circumstantial evidence for confinement. * We employ relativistic units fl = c = 1. 5-0. Bäckman et al., The nucleon-nucleon interaction and the nuclear many-body problem 7 * See the discussion in chapter 6. tThe "rule of thumb", is that in shell-model calculations the 3S interaction should be chosen-(10/6) times the 'S one, as in the Rosenfeld interaction. * The above ncan be generalized 1381 to no np(q) = a~+ 5a,,, where a+5 and a,, are Fermi creation and annihilation operators, respectively. In this way the above equation is extended to describe particle-hole excitations. * In section 4.1 we meant by the direct term the direct term of the potential in fig. 15 and eqs. (4.20), (4.21) and (4.22). From here on we refer by the direct term to the driving term enclosed in fig. 22. This terminology is in accordance with ref. [521.