Saturation of nuclear matter and realistic interactions

In this communication we study symmetric nuclear matter for the Brueckner-Hartree-Fock approach, using two realistic nucleon-nucleon interactions (CD-Bonn and Bonn C). The single-particle energy is calculated self-consistently from the real on-shell self-energy. The relation between different expressions for the pressure is studied in cold nuclear matter. For best calculations the self-energy is calculated with the inclusion of hole-hole (hh) propagation. The effects of hh contributions and a self-consistent treatment within the framework of the Green function approach are investigated. Using two different methods, namely, G-matrix and bare potential, the hh term is calculated. We found that using G-matrix brought about non-negligible contribution to the self-energy, but this difference is very small and can be ignored if compared with the large contribution coming from particle-particle term. The contribution of the hh term leads to a repulsive contribution to the Fermi energy which increases with density. For extended Brueckner-Hartree-Fock approach the Fermi energy at the saturation point fulfills the Hugenholtz-Van Hove relation.     

Random versus nonrandom competing bonds for spin glasses with long-range interactions

The mapping of random onto nonrandom competing bonds recently suggested is here implemented for spin glasses of long-ranged interactions. Exact results are obtained which support previous conclusions from high-temperature series.     

An algorithm for separable representations of realistic interactions

A general method for expanding in a separable form a local interaction is developed. The algorithm makes use of the Gamow vectors and momenta, calculated from an eigenvalue problem, and preserves the analytic properties of the original S-matrix. Applications are presented for realistic nucleon-nucleon interactions and phenomenological optical potentials. The agreement between the separable and exact scattering matrices is quite good on and off the energy shell, for a wide range of energies.     

Configuration mixing in low-lying spectra of carbon hypernuclei

<正>The spectroscopy of hypernuclear low-lying states is very important to understand the structure of hypernuclei and the hyperon impurity effect in atomic nuclei.Several novel phenomena about Λ hyperon have already been discovered by studying energy spectra and electromagnetic transitions of low-lying states in p-shell hypernuclei.One of them is the     

The Gamow shell model with realistic interactions: a theoretical framework for ab initio nuclear structure at drip-lines

Ab initio approaches are among the most advanced models to solve the nuclear many-body problem. In particular, the no-core–shell model and many-body perturbation theory have been recently extended to the Gamow shell model framework, where the harmonic oscillator basis is replaced by a basis bearing bound, resonance and scattering states, i.e. the Berggren basis. As continuum coupling is included at basis level and as configuration mixing takes care of inter-nucleon correlations, halo and resonance nuclei can be properly described with the Gamow shell model. The development of the no-core Gamow shell model and the introduction of the $\hat{\bar{Q}}$-box method in the Gamow shell model, as well as their first ab initio applications, will be reviewed in this paper. Peculiarities compared to models using harmonic oscillator bases will be shortly described. The current power and limitations of ab initio Gamow shell model will also be discussed, as well as its potential for future applications.     

Folding model potentials from realistic interactions for heavy-ion scattering

The double-folding model, with “realistic” nucleon-nucleon interactions based upon a G-matrix constructed from the Reid potential, is used to calculate the real part of the optical potential for heavy-ion scattering. The resulting potentials are shown to reproduce the observed elastic scattering for a large number of systems with bombarding energies from 5 to 20 MeV per nucleon. Some representative inelastic transitions are also reproduced. Exceptions are the elastic scattering of ⁶Li and ⁹Be for which the folded potentials must be reduced in strength by a factor of about two.The same effective interactions are shown to give a good account of two particular cases of alpha scattering as well as some cases of nucleon-nucleus scattering. Some typical examples of inelastic heavy-ion scattering are also predicted successfully.Some general properties of the folding model are reviewed and its theoretical basis is discussed. An explicit density-dependence is examined for one particular realistic interaction and found not to change the results. Single nucleon exchange is included in an approximate way and its importance is studied.In addition to being a study of the folding model, this work also provides a systematic and comprehensive optical model analysis of heavy-ion elastic scattering in this energy range.     

Fluctuation properties of spacings of low-lying nuclear levels

Fluctuation properties have been analyzed for a large collection of low-lying nuclear energy levels, with emphasis on the nearest-neighbor spacing distributions. The levels are combined in several ways to search for effects due to mass, spin, and shape. A strong mass dependence appears to be present, and there are suggestions of effects due to spin and deformation.     

石墨烯基磁量子环的低态能谱对磁场的依赖关系

我们采用狄拉克-韦尔 (Dirac-Weyl) 模型, 计算出二维石墨烯基磁量子环和磁量子点分别在垂直非均匀磁场下的低态能谱, 并讨论包括两组旋量分量的低态能谱跟磁场的依赖关系。从直接对角计算法所获得的数值结果表明, 在非均匀磁场下, 磁量子点和磁量子环的能谱中的最低朗道能级(N-=0)皆为高度简并, 且数值恒等为零。在其邻近较高的朗道能级, 磁量子环出现了由磁场诱导的轨道角动量间的跃迁, 而磁量子点则没有。最后本文指出, 除了最低朗道能级(N-=0)外, 两组旋量分量的能谱完全一样, 只是其朗道能级所标记的两组量子数不同而已。     

Three-body monopole corrections to realistic interactions

It is shown that a very simple three-body monopole term can solve practically all the spectroscopic problems-in the p, sd, and pf shells-that were hitherto assumed to need drastic revisions of the realistic potentials.     

Gamow-Teller strength with realistic nucleon-nucleon interactions

Two realistic nucleon-nucleon interactions are used to calculate the energy-weighted sum rules for the Gamow-Teller operators. There are no free parameters in our calculations. The two interactions give similar results for ⁴⁸Ca and ⁹⁰Zr.     

Random on-site interactions versus random potential in ultra cold atoms in optical lattices

We consider the physics of lattice bosons in the presence of either disordered on-site chemical potential or disordered on-site interparticle interactions. By means of analytical results using strong-coupling expansion, and numerical results based on quantum Monte Carlo calculations, we show that important qualitative changes in the zero temperature phase diagram are observed when comparing both cases. Although for both types of disorder superfluid, Mott-insulator and Bose-glass phases may be found, we show that in the case of random interactions the Mott-insulating regions shrink and eventually vanish for any finite disorder strength beyond a sufficiently large filling factor. Furthermore, at low values of the chemical potential both the superfluid and Mott insulator are stable towards the formation of a Bose-glass, leading to a possibly non-trivial tricritical point. We discuss possible experimental realizations of both types of disorder in the context of ultra cold atomic gases in optical lattices. PACS 03.75.Lm; 03.75.Ss; 05.30.Jp; 32.80.Pj     

Padé approximants and realistic effective interactions

The convergence of the J = 0, T = 1 effective interaction for sd-shell nuclei is student in terms of separate summations of infinite subseries. It is suggested that first the subset of non-folded diagrams be separately summed to all orders and that the remaining, folded diagrams be grouped according to the number of folds and expressed in terms of the former sum of non-folded diagrams and its energy derivatives. The sum of non-folded diagrams is extrapolated from the lowest three orders using the Padé approximation, and encouraging results are obtained.     

A correlated-basis-functions approach to realistic nuclear matter

The method of correlated basis functions is adapted to the nuclear-matter problem with two-nucleon potentials containing tensor as well as central components. Procedures are described for evaluating through three-body cluster order the energy expectation value with respect to a constrained trial ground-state wave function incorporating tensor and central correlations, and for calculating in two-body cluster approximation the second-order perturbation correction in a basis of likewise-correlated functions. Results for the 5100, 5200, Gammel-Christian-Thaler and Hamada-Johnston potentials are presented and dissected.     

Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots

Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions.     

g factors of nuclear low-lying states:A covariant description

The g factors and spectroscopic quadrupole moments of low-lying excited states 2+1,…,81+ in 24Mg are studied in a covariant density functional theory.The wave functions are constructed by configuration mixing of axially deformed mean-field states projected on good angular momentum.The mean-field states are obtained from the constraint relativistic point-coupling model plus BCS calculations using the PC-F1 parametrization for the particle-hole channel and a density-independent delta-force for the particle-pa...     

The projected Hartree-Fock spectra from a realistic two-body interaction

The projection method is used to obtain good angular momentum and good isospin states from the intrinsic Hartree-Fock states of the nuclei in the 2s-1d shell. An effective interaction derived from the Yale potential has been employed in the calculations. It is found that the static magnetic moments are predicted correctly. The static quadrupole moments and the lifetimes of the nuclear states for electric quadrupole transitions are predicted correctly if an effective charge of 0.5 e is ascribed to the neutrons. The projected energy spectra in even-mass nuclei are very much compressed as compared to the experimental spectra. The agreement between the projected and the experimental spectra in odd-mass nuclei is not so bad.