The self-consistent single-particle model in nuclear physics

The nuclear many body problem is treated in the single particle approximation, i.e. on the basis of the Hartree-Fock-Bogolyubov approximation. Results of various applications are presented and discussed with emphasis on properties of rotational states of deformed nuclei.     

Unified approach to nuclear densities from exotic atoms

Parameters of nuclear density distributions are derived from least-squares fits to strong interaction observables in exotic atoms. Global analyses of antiprotonic and pionic atoms show reasonably good agreement between the two types of probes regarding the average behaviour of root-mean-square radii of the neutron distributions. Apparent conflict regarding the shape of the neutron distribution is attributed to different radial sensitivities of these two probes.     

Some results with a modified self-consistent magnetic recording channel model

Self-consistent iterative simulation of the magnetic recording channel has been established as a powerful tool for the workers in this field. Though many papers have been published, even the one-dimensional model - which is especially suited for thin metallic films - can be improved or supplemented. The model presented here contains a new method of considering head sensitivities without transformation into the frequency domain and a detailed impulse analysis. With slight modifications it can be used for anisotropic materials.     

Model independent nuclear charge densities from elastic electron scattering

A method to derive nearly model independent charge densities from elastic electron scattering data is proposed and applied to ¹²C and ³²S.     

Some characteristics of nuclear densities

We propose a simple expression for nuclear densities, which brings out the following important nuclear properties: (i) shell effects in proton and neutron central densities, (ii) approximate global constancy of neutron central densities, (iii) approximate constancy ofRN ^?1/3 and R_pZ^?1/3 whereR is the nuclear half-density radius andR _p is the rms radius of the proton density, (iv) larger surface thickness and rms radius for neutron density as compared to those for proton density.     

Quadrupole-octupole rotation-vibration model with self-consistent moments of inertia

Surface excitations of deformed and transitional nuclei are studied without imposing restrictions on the amplitudes of the static deformation. The moments of inertia and vibrational moduli of elasticity of the excited states are determined in a self-consistent way by solving the set of equations that describe the interaction of quadrupole and octupole degrees of freedom due to rotations. The calculated spectra of some rigid and soft nuclei are compared with the available experimental data and calculations by other methods.     

Surface charge model of a carbon nanotube: self-consistent field from Thomas-Fermi theory

A model of a C nanotube is set up and solved self-consistently by numerical methods using the Thomas-Fermi statistical approach to treat the C 2s and 2p valence electrons. In the model presented here the C⁴⁺ ions are ‘smeared out’ uniformly over the surface of an infinitely long cylinder of radius R_t. Analytic forms of the self-consistent field are also presented far from the axis of the infinite tube, and well into its interior.     

Stripes and superconductivity in a one-dimensional self-consistent model

We show that many observable properties of high-temperature superconductors can be obtained in the framework of a one-dimensional self-consistent model with included superconducting correlations. Analytical solutions for spin, charge, and superconductivity order parameters are found. The ground state of the model at low hole doping is a spin-charge solitonic superstructure. Increased doping leads to a transition to the superconducting phase. There is a region of doping where superconductivity, spin density wave, and charged stripe structure coexist. The charge density modulation appears in the vicinity of vortices (kinks in the 1D model) in the superconducting state.     

Antiproton-nucleus scattering with self-consistent model for medium corrections

The antiproton-nucleon t-matrix with propagation in the nuclear medium is calculated selfconsistently and applied to the construction of optical potentials for the elastic scattering of antiprotons from nuclei. We find that this treatment gives results that are sensitive to medium corrections even though the strong absorption acts to mask these corrections partially. The agreement with scattering experiments at 46.8 MeV on ¹²C is very good. We compare potentials containing medium corrections to those based on free $\text{p}\text{N}$ amplitudes for ¹²C and ⁴⁰Ca. The local approximation to the optical potential is found attractive at low energies, becoming shallower with increasing bombardment energy in the range considered here (up to about E_L = 120 MeV).     

Parity dependence of nuclear level densities

A simple formula for the ratio of the number of odd- and even-parity states as a function of temperature is derived. This formula is used to calculate the ratio of level densities of opposite parities as a function of excitation energy. We test the formula with quantum Monte Carlo shell model calculations in the (pf+g(9/2)) shell. The formula describes well the transition from low excitation energies where a single parity dominates to high excitations where the two densities are equal.     

Field shift and generalised moments of nuclear charge distribution

It is shown that the use of realistic charge distribution leads to odd moment dependence of the nuclear field isotope shift. Our expression for field isotope shift reduces to the familiar result of Seltzer for low and moderateZ, Z denoting atomic number.     

Field shift and generalised moments of nuclear charge distribution

It is shown that the use of realistic charge distribution leads to odd moment dependence of the nuclear field isotope shift. Our expression for field isotope shift reduces to the familiar result of Seltzer for low and moderateZ, Z denoting atomic number.     

(Pseudo) Scalar mesons in a self-consistent NJL model

In this study, we investigate the mass spectra of π and σ mesons at finite chemical potential using the self-consistent NJL model and the Fierz-transformed interaction Lagrangian. The model introduces an arbitrary parameter α to reflect the weights of the Fierz-transformed interaction channels. We show that, when α exceeds a certain threshold value, the chiral phase transition transforms from a first-order one to a smooth crossover, which is evident from the behaviors of the chiral condensates a...     

Mesonic parton densities derived from constituent quark model constraints

Using constituent quark model constraints we calculate the gluon and sea content of pions solely in terms of their valence density and the known sea and gluon densities of the nucleon. The resulting small- predictions for and are unique and parameter free, being entirely due to QCD dynamics. Similar ideas are applied for calculating the gluon and sea content of kaons which, for our suggested choice of the kaon's valence densities, turn out to be identical to the ones of the pion. Received: 24 November 1997     

Ising model of a dilute ferromagnet in the self-consistent field approximation

The method of averaging over the exchange interaction fields has been considered as applied to clusters of one and two magnetic atoms in the Ising model of a dilute ferromagnet, and a variant of fixed-scale group renormalization on the basis of this method has been constructed. It has been shown that the approximation obtained makes it possible to distinguish models with the site and bond dilutions.     

Off-shell extension function from a generalised phase-function method

It is shown that the Combined-variable-phase-off-shell scattering theory or the generalised phase-function method provides efficient algorithms to calculate the off-shell extension function which plays a role in the theories of three-particle scattering. In order to assert this we have chosen to work with a model potential for theα-α interaction. The functions which occur in the context of our approach exhibit certain interesting features with regard to effect of the potential in producing on-and off-shell quantities like the phase shift and quasi-phase. Interpolating off-shell extension function is seen to exhibit a discontinuity where the phase function goes through a zero.