Author : P. Navratil
Publisher :
Page : 7 pages
File Size : 46,74 MB
Release : 2005
Category :
ISBN :
We review the application of effective operator formalism to the ab initio no core shell model (NCSM). For short-range operators, such as the nucleon-nucleon potential, the unitary-transformation method works extremely well at the two-body cluster approximation and good results are obtained for the binding energies and excitation spectra of light nuclei (A {
Author : Michael Karl Gerhard Kruse
Publisher : Springer Science & Business Media
Page : 135 pages
File Size : 17,89 MB
Release : 2013-09-05
Category : Science
ISBN : 3319013939
Extensions to the No-Core Shell Model presents three extensions to the No-Core Shell Model (NCSM) that allow for calculations of heavier nuclei, specifically for the p-shell nuclei. The Importance-Truncated NCSM (IT-NCSM) formulated on arguments of multi-configurational perturbation theory selects a small set of basis states from the initially large basis space in which the Hamiltonian is diagonalized. Previous IT-NCSM calculations have proven reliable, however, there has been no thorough investigation of the inherent error in the truncated IT-NCSM calculations. This thesis provides a detailed study of IT-NCSM calculations and compares them to full NCSM calculations to judge the accuracy of IT-NCSM in heavier nuclei. When IT-NCSM calculations are performed, one often needs to extrapolate the ground-state energy from the finite basis (or model) spaces to the full NCSM model space. In this thesis a careful investigation of the extrapolation procedures was performed. On a related note, extrapolations in the NCSM are commonplace, but up to recently did not have the ultraviolet (UV) or infrared (IR) physics under control. This work additionally presents a method that maps the NCSM parameters into an effective-field theory inspired framework, in which the UV and IR physics are treated appropriately. The NCSM is well-suited to describe bound-state properties of nuclei, but is not well-adapted to describe loosely bound systems, such as the exotic nuclei near the neutron drip line. With the inclusion of the Resonating Group Method (RGM), the NCSM / RGM can provide a first-principles description of exotic nuclei and the first extension of the NCSM.
Author : P. Navratil
Publisher :
Page : 14 pages
File Size : 22,44 MB
Release : 2006
Category :
ISBN :
No-core shell model (NCSM) calculations using ab initio effective interactions are very successful in reproducing experimental nuclear spectra. The main theoretical approach is the use of effective operators, which include correlations left out by the truncation of the model space to a numerically tractable size. We review recent applications of the effective operator approach, within a NCSM framework, to the renormalization of the nucleon-nucleon interaction, as well as scalar and tensor operators.
Author : Nicolas Michel
Publisher : Springer Nature
Page : 514 pages
File Size : 29,25 MB
Release : 2021-04-24
Category : Science
ISBN : 3030693562
This book provides the first graduate-level, self-contained introduction to recent developments that lead to the formulation of the configuration-interaction approach for open quantum systems, the Gamow shell model, which provides a unitary description of quantum many-body system in different regimes of binding, and enables the unification in the description of nuclear structure and reactions. The Gamow shell model extends and generalizes the phenomenologically successful nuclear shell model to the domain of weakly-bound near-threshold states and resonances, offering a systematic tool to understand and categorize data on nuclear spectra, moments, collective excitations, particle and electromagnetic decays, clustering, elastic and inelastic scattering cross sections, and radiative capture cross sections of interest to astrophysics. The approach is of interest beyond nuclear physics and based on general properties of quasi-stationary solutions of the Schrödinger equation – so-called Gamow states. For the benefit of graduate students and newcomers to the field, the quantum-mechanical fundamentals are introduced in some detail. The text also provides a historical overview of how the field has evolved from the early days of the nuclear shell model to recent experimental developments, in both nuclear physics and related fields, supporting the unified description. The text contains many worked examples and several numerical codes are introduced to allow the reader to test different aspects of the continuum shell model discussed in the book.
Author : Matthew Burrows
Publisher :
Page : 180 pages
File Size : 31,80 MB
Release : 2020
Category : Effective interactions (Nuclear physics)
ISBN :
The first complete ab initio leading-order effective interactions for protons or neutrons on light spin-0 nuclei are presented. The technological advances leading to this result are described in detail starting with the nonlocal momentum distributions created from No Core Shell Model (NCSM) reduced matrix elements. The effective potential is calculated using the leading-order of the multiple scattering approach with the NN amplitudes expressed in terms of Wolfenstein amplitudes. In order for the effective interaction to be ab initio, the complete NN interaction enters both the reaction as well as the structure calculation on equal footing. Elastic scattering amplitudes for this work are mostly limited 100 to 200 MeV projectile kinetic energy to be consistent with a leading-order calculation. This work for the first time takes into account the spin of the struck target nucleon in a realistic calculation. Elastic scattering observables for closed-shell nuclei 4He and 16O are given along with a comparison to previous assumptions that neglect the spin of the struck nucleon. The same observables for open-shell nuclei 12C, 6He, and 8He are presented with the same comparison. It is found that the difference between a complete ab initio calculation and one that neglects the spin of the struck nucleon is small for nuclei that have equal numbers of protons and neutrons. For nuclei with N , Z, the effect of the spin from the struck nucleon is energy dependent and significant at lower energies. The quality of the first leading-order ab initio effective interaction calculation to predict scattering observables is found to be good for the studied range of energies and nuclei and for the NN interaction chosen for this work.
Author : David J. Rowe
Publisher : World Scientific
Page : 677 pages
File Size : 38,12 MB
Release : 2010
Category : Science
ISBN : 9812569553
This book reviews the basic models and theories of nuclear structure and gives an in-depth analysis of their experimental and mathematical foundations. It shows the relationships between the models and exhibits the value of following the strategy of: looking for patterns in all the data available, developing phenomenological models to explain them, and finally giving the models a foundation in a fundamental microscopic theory of interacting neutrons and protons. This unique book takes a newcomer from an introduction to nuclear structure physics to the frontiers of the subject along a painless path. It provides both the experimental and mathematical foundations of the essential models in a way that is accessible to a broad range of experimental and theoretical physicists. Thus, the book provides a unique resource and an exposition of the essential principles, mathematical structures, assumptions, and observational data on which the models and theories are based. It avoids discussion of many non-essential variations and technical details of the models.
Author : A. Ansari
Publisher : Alpha Science Int'l Ltd.
Page : 454 pages
File Size : 40,26 MB
Release : 2005
Category : Science
ISBN : 9788173195969
Contributed articles presented in a workshop organised by Institute of Physics, Bhubaneswar, held during Mar. 10-22, 2003.
Author : Carl J. Gross
Publisher : Springer Science & Business Media
Page : 756 pages
File Size : 28,61 MB
Release : 2007-12-10
Category : Science
ISBN : 3540376429
The International Conference on Exotic Nuclei and Atomic Masses (ENAM) has gained the status of the premier meeting for the physics of nuclei far from stability. The selected and refereed papers presenting the main results constitute valuable proceedings that offer everyone working in this field an authoritative and comprehensive source of reference.
Author :
Publisher :
Page : 66 pages
File Size : 35,25 MB
Release : 2009
Category :
ISBN :
We present an overview of recent results and developments of the no-core shell model (NCSM), an ab initio approach to the nuclear many-body problem for light nuclei. In this aproach, we start from realistic two-nucleon or two- plus three-nucleon interactions. Many-body calculations are performed using a finite harmonic-oscillator (HO) basis. To facilitate convergence for realistic inter-nucleon interactions that generate strong short-range correlations, we derive effective interactions by unitary transformations that are tailored to the HO basis truncation. For soft realistic interactions this might not be necessary. If that is the case, the NCSM calculations are variational. In either case, the ab initio NCSM preserves translational invariance of the nuclear many-body problem. In this review, we, in particular, highlight results obtained with the chiral two- plus three-nucleon interactions. We discuss efforts to extend the applicability of the NCSM to heavier nuclei and larger model spaces using importance-truncation schemes and/or use of effective interactions with a core. We outline an extension of the ab initio NCSM to the description of nuclear reactions by the resonating group method technique. A future direction of the approach, the ab initio NCSM with continuum, which will provide a complete description of nuclei as open systems with coupling of bound and continuum states is given in the concluding part of the review.
Author : Gerald E. Brown
Publisher : World Scientific
Page : 608 pages
File Size : 25,63 MB
Release : 2010
Category : Science
ISBN : 9814289280
This book provides a comprehensive overview of some key developments in the understanding of the nucleon-nucleon interaction and nuclear many-body theory. The main problems at the level of meson exchange physics have been solved, and we have an effective field theory using a phenomenological interaction pioneered by Achim Schwenk and Scott Bogner, which is nearly universally accepted as a unique low-momentum interaction that includes all experimental data to date.This understanding is based on a multi-step development in which different scientific insights and a wide range of physical and mathematical methodologies fed into each other. It is best appreciated by looking at the different 'steps along the way', starting with the pioneering work of Brueckner and his collaborators that was just as necessary and important as the insightful masterly improvements to Brueckner's theory by Hans Bethe and his students. Moving on from there, the off-shell effects that bedeviled Bethe's work — which had resulted in the 1963 Reference Spectrum Method — were treated relatively accurately by introducing an energy gap between initial bound states and an intermediate state. With their influential 1967 paper, Brown and Kuo prepared the effective field theory. Later, the introduction of 'Brown-Rho scaling' deepened understanding of saturation in the many-body system and fed directly into recent work on carbon-14 dating.
