Simple models for shell-model configuration densities

doi:10.1103/PHYSREVC.74.067302

Title: Simple models for shell-model configuration densities

Full Record
Other Related Research

Abstract

We consider the secular behavior of shell-model configuration (partial) densities. When configuration densities are characterized by their moments, one often finds large third moments (asymmetries), which make suitable parametrization of the secular behavior problematic. We review several parameterizations or models and compare to exact numerical configuration densities. We propose a modified Breit-Wigner form which provides a better secular approximation, for large asymmetries, compared to models based on Gaussian forms.

Authors:

Teran, Edgar; Johnson, Calvin W. ^[1]

Department of Physics, San Diego State University, 5500 Campanile Drive, San Diego, California 92182-1233 (United States)

Publication Date:: Fri Dec 15 00:00:00 EST 2006

OSTI Identifier:: 20864249

Resource Type:: Journal Article

Resource Relation:: Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 74; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevC.74.067302; (c) 2006 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; APPROXIMATIONS; ASYMMETRY; BREIT-WIGNER FORMULA; COMPARATIVE EVALUATIONS; DENSITY; ENERGY-LEVEL TRANSITIONS; REVIEWS; SHELL MODELS; STATISTICAL MODELS

Citation Formats


                    Teran, Edgar, and Johnson, Calvin W. Simple models for shell-model configuration densities.  United States: N. p., 2006. 
        Web.  doi:10.1103/PHYSREVC.74.067302.

Copy to clipboard


                    Teran, Edgar, & Johnson, Calvin W. Simple models for shell-model configuration densities.  United States.  doi:10.1103/PHYSREVC.74.067302.

Copy to clipboard


                    Teran, Edgar, and Johnson, Calvin W. Fri .  
        "Simple models for shell-model configuration densities".  United States.  
        doi:10.1103/PHYSREVC.74.067302.

Copy to clipboard


                    
@article{osti_20864249,

  title        = {Simple models for shell-model configuration densities},

  author       = {Teran, Edgar and Johnson, Calvin W.},

  abstractNote = {We consider the secular behavior of shell-model configuration (partial) densities. When configuration densities are characterized by their moments, one often finds large third moments (asymmetries), which make suitable parametrization of the secular behavior problematic. We review several parameterizations or models and compare to exact numerical configuration densities. We propose a modified Breit-Wigner form which provides a better secular approximation, for large asymmetries, compared to models based on Gaussian forms.},

  doi          = {10.1103/PHYSREVC.74.067302},

  journal      = {Physical Review. C, Nuclear Physics},

  number       = 6,

  volume       = 74,

  place        = {United States},

  year         = {Fri Dec 15 00:00:00 EST 2006},

  month        = {Fri Dec 15 00:00:00 EST 2006}

}

Copy to clipboard

Journal Article:

DOI: 10.1103/PHYSREVC.74.067302

Other availability

Find in Google Scholar

Search WorldCat to find libraries that may hold this journal

Save / Share:

Export Metadata

Save to My Library

Similar records in OSTI.GOV collections:

Parity-projected shell model Monte Carlo level densities for fp-shell nuclei

Journal Article Oezen, C. ; Martinez-Pinedo, G. ; Langanke, K. ; ... - Physical Review. C, Nuclear Physics

We calculate parity-dependent level densities for the even-even isotopes {sup 58,62,66}Fe and {sup 58}Ni and the odd-A nuclei {sup 59}Ni and {sup 65}Fe using the shell model Monte Carlo method. We perform these calculations in the complete fp-gds shell-model space using a pairing+quadrupole residual interaction. We find that, due to pairing of identical nucleons, the low-energy spectrum is dominated by positive parity states. Although these pairs break at around the same excitation energy in all nuclei, the energy dependence of the ratio of negative-to-positive parity level densities depends strongly on the particular nucleus of interest. We find equilibration of bothmore »« less
DOI: 10.1103/PHYSREVC.75.064307
Particle-Number Reprojection in the Shell Model Monte Carlo Method: Application to Nuclear Level Densities

Journal Article Alhassid, Y. ; Liu, S. ; Nakada, H. - Physical Review Letters

We introduce a particle-number reprojection method in the shell model Monte Carlo that enables the calculation of observables for a series of nuclei using a Monte Carlo sampling for a single nucleus. The method is applied to calculate nuclear level densities in the complete (pf+g{sub 9/2}) -shell using a good-sign Hamiltonian. Level densities of odd-A and odd-odd nuclei are reliably extracted despite an additional sign problem. Both the mass and the T{sub z} dependence of the experimental level densities are well described without any adjustable parameters. The odd-even staggering observed in the calculated backshift parameter follows the experimental data moremore »« less
DOI: 10.1103/PhysRevLett.83.4265
Spin Projection in the Shell Model Monte Carlo Method and the Spin Distribution of Nuclear Level Densities

Journal Article Alhassid, Y. ; Liu, S. ; Nakada, H. - Physical Review Letters

We introduce spin projection methods in the shell model Monte Carlo approach and apply them to calculate the spin distribution of level densities for iron-region nuclei using the complete (pf+g{sub 9/2}) shell. We compare the calculated distributions with the spin-cutoff model and extract an energy-dependent moment of inertia. For even-even nuclei and at low excitation energies, we observe a significant suppression of the moment of inertia and odd-even staggering in the spin dependence of level densities.
DOI: 10.1103/PHYSREVLETT.99.162504
The shell model Monte Carlo approach to level densities: from medium-mass to heavy deformed nuclei

Journal Article Alhassid, Y. - AIP Conference Proceedings

The shell model Monte Carlo (SMMC) approach is a powerful state-of-the-art method for the microscopic calculation of level densities in the presence of correlations. With this method it is possible to perform realistic calculations in model spaces that are many orders of magnitude larger than spaces that can be treated with conventional diagonalization methods. SMMC level densities of medium-mass nuclei were found to be in remarkably good agreement with experimental level densities without any adjustable parameters. We discuss recent developments, including a spin projection method for calculating the spin distribution of level densities and the extension of SMMC to heavymore » deformed nuclei.« less
DOI: 10.1063/1.2920744
Isospin-projected nuclear level densities by the shell model Monte Carlo method

Journal Article Nakada, H. ; Alhassid, Y. - Physical Review. C, Nuclear Physics

We have developed an efficient isospin projection method in the shell model Monte Carlo approach for isospin-conserving Hamiltonians. For isoscalar observables this method has the advantage of being exact sample by sample. It allows us to take into account the proper isospin dependence of the nuclear interaction, thus avoiding a sign problem that such an interaction introduces in unprojected calculations. We apply the method to calculate the isospin dependence of level densities in the complete pf+g{sub 9/2} shell. We find that isospin-dependent corrections to the total level density are particularly important for N{approx}Z nuclei.
DOI: 10.1103/PHYSREVC.78.051304

Similar Records