Advanced search options

You searched for `subject:(coherent adiabatic mixing)`

. One record found.

▼ Search Limiters

Louisiana State University

1. Gueorguiev, Vesselin Gueorguiev. Mixed-symmetry shell-model calculations in nuclear physics.

Degree: PhD, Physical Sciences and Mathematics, 2002, Louisiana State University

URL: etd-1028102-183920 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1990

Advances in computer technologies allow calculations in ever larger model spaces. To keep our understanding growing along with this growth in computational power, we consider a novel approach to the nuclear shell model. The one-dimensional harmonic oscillator in a box is used to introduce the concept of an oblique-basis shell-model theory. By implementing the Lanczos method for diagonalization of large matrices, and the Cholesky algorithm for solving generalized eigenvalue problems, the method is applied to nuclei. The mixed-symmetry basis combines traditional spherical shell-model states with SU(3) collective configurations. We test the validity of this mixed-symmetry scheme on ^{24}Mg and ^{44}Ti. Results for ^{24}Mg, obtained using the Wilthental USD intersection in a space that spans less than 10% of the full-space, reproduce the binding energy within 2% as well as an accurate reproduction of the low-energy spectrum and the structure of the states – 90% overlap with the exact eigenstates. In contrast, for an m-scheme calculation, one needs about 60% of the full space to obtain compatible results. Calculations for ^{44}Ti support the mixed-mode scheme although the pure SU(3) calculations with few irreps are not as good as the standard m-scheme calculations. The strong breaking of the SU(3) symmetry results in relatively small enhancements within the combined basis. However, an oblique-basis calculation in 50% of the full pf-shell space is as good as a usual m-scheme calculation in 80% of the space. Results for the lower pf-shell nuclei ^{44-48}Ti and ^{48}Cr, using the Kuo-Brown-3 interaction, show that SU(3) symmetry breaking in this region is driven by the single-particle spin-orbit splitting. In our study we observe some interesting coherent structures, such as coherent mixing of basis states, quasi-perturbative behavior in the toy model, and enhanced B(E2) strengths close to the SU(3) limit even though SU(3) appears to be rather badly broken. The results suggest that a mixed-mode shell-model theory may be useful in situations where competing degrees of freedom dominate the dynamics, and full-space calculations are not feasible.

Subjects/Keywords: confinement; coherent (adiabatic) mixing; elliott su(3) model; spherical and cylindrical symmetry; spectrum; b(e2) transition strengths; quadrupole-quadrupole interaction; generalized eigenvalue problem; quasi-symmetry; harmonic oscillator in a box; cholesky; spin-orbit interaction; numerical methods; oblique; nuclear shell models; lanczos; nuclear structure; ground state energy; nuclear physics

Record Details Similar Records

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Gueorguiev, V. G. (2002). Mixed-symmetry shell-model calculations in nuclear physics. (Doctoral Dissertation). Louisiana State University. Retrieved from etd-1028102-183920 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1990

Chicago Manual of Style (16^{th} Edition):

Gueorguiev, Vesselin Gueorguiev. “Mixed-symmetry shell-model calculations in nuclear physics.” 2002. Doctoral Dissertation, Louisiana State University. Accessed December 04, 2020. etd-1028102-183920 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1990.

MLA Handbook (7^{th} Edition):

Gueorguiev, Vesselin Gueorguiev. “Mixed-symmetry shell-model calculations in nuclear physics.” 2002. Web. 04 Dec 2020.

Vancouver:

Gueorguiev VG. Mixed-symmetry shell-model calculations in nuclear physics. [Internet] [Doctoral dissertation]. Louisiana State University; 2002. [cited 2020 Dec 04]. Available from: etd-1028102-183920 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1990.

Council of Science Editors:

Gueorguiev VG. Mixed-symmetry shell-model calculations in nuclear physics. [Doctoral Dissertation]. Louisiana State University; 2002. Available from: etd-1028102-183920 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1990