摘要:

This article contains brief comments on Stewart Bloom’s contributions to the Livermore Physics Department. Emphasis is placed on his enthusiasm for physics and his encouragement of others at the lab.(AIP)

ISSN:0094-243X    

DOI:10.1063/1.41438

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

I review the major events in my personal history which more‐or‐less determined my particular career in physics. Much of the emphasis is on &bgr;‐decay, since so much of my work, both experimental and theoretical has been bound up in this subject.

ISSN:0094-243X    

DOI:10.1063/1.41441

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.41448

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We discuss two versions of relativistic nuclear mean field theory, and implications for the nuclear equation of state (EOS). The well‐known Walecka model gives too stiff an EOS, unless supplemented by additional non‐linear terms in the Lagrangian. A modification of this model suggested by Zimanyi leads to a softer EOS with no free parameters (once the energy and density of nuclear matter is fixed). However, it appears to give too small nuclear spin‐orbit coupling. The scalar coupling constant appearing in either theory can be derived using the Nambu‐Jona‐Lasigno model, and it appears to be fairly close to the empirical values appearing in either version of the mean field theory. Finally, we remark on the approximate validity of pseudospin in nuclei, which is of interest in connection with superdeformed nuclei. It turns out that the scalar coupling constant in the mean field theory is close to the value required for pseudospin to be valid.

ISSN:0094-243X    

DOI:10.1063/1.41437

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This article contains the history of two computer programs developed to perform large scale configuration interaction calculations—Cornelius and Vladimir.(AIP)

ISSN:0094-243X    

DOI:10.1063/1.41439

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The shell model/R‐matrix technique of calculating nuclear reaction cross sections for light projectiles incident on light nuclei is discussed, particularly in the application of the technique to thermonuclear reactions. Details are presented on the computational methods for the shell model which display how easily the calculations can be performed. Results of the shell model/R‐matrix technique are discussed as are some of the problems encountered in picking an appropriate nucleon‐nucleon interaction for the large model spaces which must be used for current problems. The status of our work on developing an effective nucleon‐nucleon interaction for use in large‐basis shell model calculations is presented. This new interaction is based on a combination of global constraints and microscopic nuclear data.

ISSN:0094-243X    

DOI:10.1063/1.41440

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Nucleon‐nucleon bremsstrahlung, NN&ggr;, is fundamental process, which involves the strong and electromagnetic fields acting simultaneously. Since the electromagnetic interaction is well known, NN&ggr; provides a calculable tool for comparing off‐energy‐shell (OES) effects from different two‐nucleon potentials compared to experiment and also provides a simple testing ground, which is sensitive to meson‐exchange‐current (MEC) contributions that are so important in electronuclear physics. MEC effects, which are included by requiring gauge invariance of the complete np&ggr; amplitude and which increase the cross section by a factor greater than two, are shown to order K° in the photon momentum at 200 MeV. pp&ggr; calculations are compared to the 280 MeV experimental results from TRIUMF, which use a polarized proton beam, and which contain ‘‘large’’ OES effects. Potentials with different short‐range radial behavior are compared in order to examine the penetration of the photon radiation. Rather good agreement with experiment for the Bonn potential is achieved without the arbitrary normalization of 2/3 applied to the TRIUMF cross‐section data. The rescattering included in our work accounts for an increase of up to approximately 20% in the cross section, and it contributes up to a factor of 2.5 in the analyzing power.

ISSN:0094-243X    

DOI:10.1063/1.41442

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Methods for dealing with the complex problems posed by shell model calculations in huge bases are discussed. Straightforward approaches involving diagonalization of large matrices are not yet feasible, but sampling techniques allow the calculation of many quantities with sufficient accuracy to allow tests of predictions against data in the areas of strength functions and level densities.

ISSN:0094-243X    

DOI:10.1063/1.41443

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This paper contains some recollections and comments concerning the problem of the missing Gamow‐Teller strength. The discussion is placed in the context of the Livermore shell model code. It is pointed out that conventional shell model calculations place all of the strength required by the Gamow‐Teller sum rule at fairly low excitations. Thus, failure to find all of the missing strength below about 20 MeV signifies a breakdown of that model approach in its standard form. Although approaches to understanding the problem do not single out individual causes so cleanly as to point to a ‘‘smoking gun,’’ there is a distinction between those that ignore nucleon structure and those that exploit nucleon structure. A fully adequate model of GT transitions does not yet exist.

ISSN:0094-243X    

DOI:10.1063/1.41444

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The renormalized coupling strength of the &bgr;‐decay axial vector current is related to &pgr;± p cross sections through the Adler‐Weisberger sum rule, that follows from chiral symmetry. We attempt to understand the Adler‐Weisberger sum rule in the 1/Ncexpansion in QCD, and in Skyrme‐Witten model that realizes the 1/Ncexpansion in the low energy limit, using it to explicitly calculate both gAand the &pgr;± p cross sections.

ISSN:0094-243X    

DOI:10.1063/1.41445

出版商:AIP    

年代:1991

数据来源: AIP