Realistic nuclear Hamiltonian: Ab exitu approach

Fully-microscopic no-core shell model (NCSM) calculations of all stable s and p shell nuclei are used to determine a realistic NN   interaction, JISP16, describing not only the two-nucleon data but the binding energies and spectra of nuclei with A?16$A?16$ as well. The JISP16 interaction, providing rapid convergence of the NCSM calculations, is obtained in an ab exitu approach by phase-equivalent transformations of the JISP6 NN interaction.     

Description of resonant states in the shell model

A technique for describing scattering states within the nuclear shell model is proposed. This technique is applied to scattering of nucleons by particles based on ab initio No-Core Shell Model calculations of ⁵He and ⁵Li nuclei with JISP16 NN interaction.     

Nonlocal nucleon-nucleon interaction JISP

The J-matrix inverse scattering formalism is described and a new type of nucleon-nucleon interaction JISP is constructed within its framework. Interaction for each partial NN scattering is represented by a small matrix in the oscillator basis, which allows its direct use in multiparticle shell-model calculations and in calculations within the resonating group approximation. The JISP reproduces np scattering data and deuteron characteristics with an accuracy of modern realistic NN potentials (x ²/datum = 1.05). The generalization of this interaction which takes into account violation of charge independence of nucleon-nucleon forces is proposed and pp scattering phases calculated with this new charge-dependent interaction CD-JISP are discussed.     

JISP16 realistic <Emphasis Type="Italic">NN</Emphasis> interaction within the resonating group approach to the α + n scattering

An approach is developed which allows the JISP16 realistic NN interaction to be included in calculations within the algebraic version of the resonating group approach. A particular α + n system is examined. The approach is based on the use of the generating function method. The results obtained can be generalized to the case of more complicated systems and included in calculations of potentials with separable coordinate dependence.     

Benchmark of the No-Core Monte Carlo Shell Model in Light Nuclei

We report the benchmark comparison of the properties in light nuclei among the Monte Carlo Shell Model, Full Configuration Interaction and No Core Full Configuration approaches. For this benchmark process, we compare results for the energies of 9 states from helium-4 to carbon-12 that includes 7 ground states and 2 excited states. The JISP16 NN interaction is adopted. The Coulomb and all other interactions are neglected. The contributions of spurious center-of-mass excitation are not discussed here. The basis space is truncated by the cutoff of the single-particle basis space, N _shell. We select the optimal ?ω that minimizes the energy for that state and basis space cutoff. The MCSM results are obtained by exploiting the recent development in the computation of two-body matrix elements between non-orthogonal Slater determinants and technique of the energy-variance extrapolation. All results are found to be consistent with each other to within quoted uncertainties when they could be quantified. As an exploratory attempt, we also demonstrate how to draw the intrinsic density from no-core MCSM wave functions by taking the ⁸Be ground state as an example.     

Phase-equivalent transformation which does not affect bound state properties and its manifestation in many-body systems

We propose a phase-equivalent transformation of NN interaction of a new type, the DET-PET transformation, which does not affect the wave function of the bound system (deuteron). The DET-PET properties and its manifestation in many-body systems are studied. In particular, we investigate the correlation of the ³H and ⁴He binding energies (the Tjon line) in calculations with NN potentials obtained by means of DET-PET from the JISP16 NN interaction.     

Light nuclei in <Emphasis Type="Italic">ab initio</Emphasis> approach with realistic inverse scattering <Emphasis Type="Italic">NN</Emphasis>-interaction

We discuss the studies of light nuclei in ab initio No-core Full Configuration approach based on extrapolations to the infinite model space of large-scale No-core Shell Model calculations on supercomputers. The convergence at the end of p shell and beginning of the sd shell can be achieved if only reasonable soft enough NN interactions are used. In particular, good predictions are obtained with a realistic JISP16 NN interaction obtained in J-matrix inverse scattering approach and fitted to reproduce light nuclei observables without three-nucleon forces. We discuss the current status of this NN interaction and its recent development.     

Evidence for symplectic symmetry in Ab initio no-core shell model results for light nuclei

Clear evidence for symplectic symmetry in low-lying states of 12C and 16O is reported. Eigenstates of 12C and 16O, determined within the framework of the no-core shell model using the J-matrix inverse scattering potential with A相似文献   

Effects of quark-antiquark pair annihilation inπ N Scattering

The(q¯ q) creation and annihilation terms of the one-gluon-exchange Lagrangian are incorporated into the quark cluster model. A resonating group study of theπ N interaction within this extended model yields scattering phase shifts which are in qualitative agreement with experiment without any parameter adjustment.     

Magnetic polaron structures in the one-dimensional double and super-exchange model

An analytical and numerical study of the one-dimensional double and super-exchange model is presented. A phase separation between ferromagnetic and anti-ferromagnetic phases occurs at low super-exchange interaction energy. When the super-exchange interaction energy gets larger, the conduction electrons are self-trapped within separate small magnetic polarons. These magnetic polarons contain a single electron inside two or three sites depending on the conduction electron density and form a Wigner crystallization. A new phase separation is found between these small polarons and the anti-ferromagnetic phase. Our results could explain the spin-glass-like behavior observed in the nickelate one-dimensional compound Y _2?xCa_xBaNiO₅.     

A two-particle exchange interaction model

The magnetisation reversal of two interacting particles was investigated within a simple model describing exchange coupling of magnetically uniaxial single-domain particles. Depending on the interaction strength W, the reversal may be cooperative or non-cooperative. A non-collinear reversal mode is obtained even for two particles with parallel easy axes. The model yields different phenomena as observed in spring magnets such as recoil hysteresis in the second quadrant of the field-magnetisation-plane, caused by exchange bias, as well as the mentioned reversal-rotation mode. The Wohlfarth’s remanence analysis performed on aggregations of such pairs of interacting particles shows that the deviation δM(H_m) usually being considered as a hallmark of magnetic interaction vanishes for all maximum applied fields H_m not only at W=0, but also for sufficiently large values of W. Furthermore, this so-called δM-plot depends on whether the sample is ac-field or thermally demagnetised.     

Extension of the logarithmic potential to multiquark systems: Dependence of the energy on depth and range

Quigg and Rosner have recently examined the problem of constructing a quark model consistent with the experimental finding that M(?′) ? M(?) ≈ M(Ψ?) ? M(Ψ). They have shown that an energy spectrum with level spacing independent of the mass of the consituent quarks occurs if the potential has a logarithmic shape. Lipkin in a recent letter has attempted to extend the Quigg-Rosner model to multiquark systems by assuming a quasinuclear model with a two-body logarithmic interaction and no additional forces (or bag). In this note we examine some of the features of this two-body interaction and their generalization within the type of quasinuclear model suggested by Lipkin.     

RPA description of the electric polarizability of the nucleon

Excited states of the nucleon are described as RPA configurations on a mean-field ground state taken from the MIT bag model. A residual interaction of a structure as in the Nambu-Jona-Lasinio model is used. The particlehole states are coupled to good total angular momentum and isospin. Valence excitations of particle-hole type and quark-antiquark (q $\bar q$ ) states from the Dirac-sea are included. The dependence of the baryon spectrum and multipole response functions on the coupling constantG is studied. At critical values ofG the 3q-ground state becomes degenerate with strongly collectiveq99-2 modes. The model is used to calculate the averaged electric polarizability of the neutron and the protonα. Without residual interactionα=7·10^?4 fm ³ is found. With residual interaction the value increases toα=(?11)·10^?4 fm ³. The measured value ofα is reproduced within experimental error bars.     

Lattice dynamics of LaMnO3: Coupling of the lattice and orbital degrees of freedom

The lattice dynamics of regular LaMnO₃ is calculated within a shell model with pairwise interionic interaction potentials and with a Jahn-Teller (JT) contribution included into the energy and dynamic matrix of the crystal. A correlation is made between Raman spectral lines and lattice vibrations. The positions of some lines in the Raman spectrum are found to depend heavily on the linear JT coupling constant V _e . The effect of the JT coupling on the phonon density of states of LaMnO₃ is investigated.     

The hyperon-nucleon interaction potential in the bound-state soliton model: the ΛN case

We develop the formalism to study the hyperon-nucleon interaction potential within the bound-state approach to the SU(3) Skyrme model. The general framework is illustrated by applying it to the diagonal ΛN potential. The central, spin-spin and tensor components of this interaction are obtained and compared with those derived using alternative schemes.     

Approximation of the microscopic effective pairing interaction by the off-shell T matrix for free nucleon-nucleon scattering

The effective pairing interaction in the ¹ S ₀ channel as calculated microscopically within the Brueckner method for a planar slab of nuclear matter by using the separable version of the Paris nucleon-nucleon potential is investigated. The effective interaction is determined for the model space including all negative-energy single-particle states. An analysis is performed for two values of the chemical potential, μ=?8 and ?4 MeV. It is shown that, to a high precision, the effective interaction can be approximated by the off-shell T matrix for free nucleon-nucleon interaction, the T matrix in question being taken at a negative value of the total energy of two nucleons E=2μ.