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Title: Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach

Abstract

The relation between energy and density (known as the nuclear equation of state) plays a major role in a variety of nuclear and astrophysical systems. Spin and isospin asymmetries can have a dramatic impact on the equation of state and possibly alter its stability conditions. An example is the possible manifestation of ferromagnetic instabilities, which would indicate the existence, at a certain density, of a spin-polarized state with lower energy than the unpolarized one. This issue is being discussed extensively in the literature and the conclusions are presently very model dependent. We will report and discuss our recent progress in the study of spin-polarized neutron matter. The approach we take is microscopic and relativistic. The calculated neutron matter properties are derived from realistic nucleon-nucleon interactions. This makes it possible to understand the properties of the equation of state in terms of specific features of the nuclear force model.

Authors:
;  [1];  [2]
  1. Physics Department, University of Idaho, Moscow, Idaho 83844 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20995128
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.034315; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ASYMMETRY; DENSITY; EQUATIONS OF STATE; HARTREE-FOCK METHOD; ISOSPIN; NUCLEAR FORCES; NUCLEAR MATTER; NUCLEON-NUCLEON INTERACTIONS; RELATIVISTIC RANGE; SPIN; SPIN ORIENTATION

Citation Formats

Sammarruca, F., Krastev, P. G., and Physics Department, Texas A and M University-Commerce, Commerce, Texas 75429-3011. Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.034315.
Sammarruca, F., Krastev, P. G., & Physics Department, Texas A and M University-Commerce, Commerce, Texas 75429-3011. Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach. United States. doi:10.1103/PHYSREVC.75.034315.
Sammarruca, F., Krastev, P. G., and Physics Department, Texas A and M University-Commerce, Commerce, Texas 75429-3011. Thu . "Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach". United States. doi:10.1103/PHYSREVC.75.034315.
@article{osti_20995128,
title = {Spin polarized neutron matter within the Dirac-Brueckner-Hartree-Fock approach},
author = {Sammarruca, F. and Krastev, P. G. and Physics Department, Texas A and M University-Commerce, Commerce, Texas 75429-3011},
abstractNote = {The relation between energy and density (known as the nuclear equation of state) plays a major role in a variety of nuclear and astrophysical systems. Spin and isospin asymmetries can have a dramatic impact on the equation of state and possibly alter its stability conditions. An example is the possible manifestation of ferromagnetic instabilities, which would indicate the existence, at a certain density, of a spin-polarized state with lower energy than the unpolarized one. This issue is being discussed extensively in the literature and the conclusions are presently very model dependent. We will report and discuss our recent progress in the study of spin-polarized neutron matter. The approach we take is microscopic and relativistic. The calculated neutron matter properties are derived from realistic nucleon-nucleon interactions. This makes it possible to understand the properties of the equation of state in terms of specific features of the nuclear force model.},
doi = {10.1103/PHYSREVC.75.034315},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Spin-polarized isospin asymmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. After a brief review of the formalism, we present and discuss the self-consistent single-particle potentials at various levels of spin and isospin asymmetry. We then move to predictions of the energy per particle, also under different conditions of isospin and spin polarization. Comparison with the energy per particle in isospin symmetric or asymmetric unpolarized nuclear matter shows no evidence for a phase transition to a spin-ordered state, neither ferromagnetic nor antiferromagnetic.
  • The relativistic microscopic optical potential (RMOP) is studied within the framework of the Dirac-Brueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nuclear self-energy in the DBHF is extended to asymmetric nuclear matter calculations. A nucleon effective interaction is introduced to reproduce the results of the G matrix. The real part of nucleon self-energy in asymmetric nuclear matter is calculated with the G matrix in the Hartree-Fock approach, while the imaginary part is obtained from the polarization diagram. Nuclear optical potentials in finite nuclei are derived from the self-energies in asymmetric matter through a local-density approximation. The differentialmore » cross sections and the analyzing powers in p+{sup 40}Ca and p+{sup 208}Pb elastic scattering at E{sub p}{<=}200 MeV are studied with these RMOPs. A satisfactory agreement with the experimental data is found. This is achieved without readjusting phenomenologically the RMOP derived from the DBHF plus polarization diagram.« less
  • The microscopic optical model potential (OMP) of {alpha}-nucleus elastic scattering based on a double-folding model (DFM) is studied. The nucleon OMPs in nuclear matter as well as the nucleon-nucleon (NN) effective interaction are calculated in the framework of the Dirac-Brueckner-Hartree-Fock (DBHF) approach, in which the density and energy dependence is parametrized by polynomial expansions. The microscopic OMP of nucleus-nucleus scattering is obtained by doubly folding the complex NN effective interaction with respect to the densities of both projectile and target nuclei. An improved local-density approximation is adopted to take account of the finite-range correction. Renormalization factors on the real andmore » imaginary OMP are introduced to obtain the best fit to the experimental data. A systematic analysis of {sup 4}He elastic scattering off {sup 12}C, {sup 16}O, {sup 28}Si, and {sup 40}Ca is performed. The calculated cross sections over a wide range of incident energies and scattering angles are in good agreement with the experimental data, which confirms the applicability of this model. Moreover, for the same projectile and target, the renormalization factors are found to be almost constant at various incident energies.« less
  • The model-space Brueckner-Hartree-Fock (BHF) approach of nuclear matter is extended to asymmetric nuclear matter. The energy per nucleon of bulk nuclear matter is calculated over a wide range of density and asymmetry parameter with both the Reid soft-core and the Paris nucleon-nucleon interactions. The results are compared to those calculated by using the usual BHF approach.