Dependence of Isoscaling Parameters on Nucleon-Nucleon Cross Section and Momentum-Dependent Interaction

Inltuences of the isospin dependence of the in-medium nucleon-nucleon cross section and the momentum-dependent interaction （MDI） on the isotope scaling are investigated by using the isospin-dependent quantum molecular dynamics model （IQMD）. The results show that both the isospin dependence of the in-medium nucleon-nucleon cross section and the momentum-dependent interaction affect the isoscaling parameters appreciably and indepen- dently. The inltuence caused by the isospin dependence of two-body collision is relatively larger than that from the MDI in the mean tield. Aiming at exploring the implication of isoscaling behaviour, which the statistical equilibrium in the reaction is reached, the statistical properties in the mass distribution and the kinetic energy distribution of the fragments simulated by IQMD are presented.     

Models of πNN interactions

A NN model inspired by Quantum Chromodynamics is presented. The model gives an accurate fit to the most recent Arndt NN phase shifts up to 1 GeV and can be applied to study intermediate- and high-energy nuclear reactions.Invited talk to the symposium Mesons and Light Nuclei IV, Bechyn, Czechoslovakia, September 5–10, 1988.This work is supported by the U.S. Department of Energy, Nuclear Physics Division, under contract W-31-109-ENG-38.     

Weak Finite—Size Dependence of Velocity and Strong Phase Dependence of Central Charge

We study the finite-size scaling behavior of velocity and central charge for different coupling constants and different phases in (1 1)-dimensional lattice model in very short chains.Using XXZ spin 1/2 chains with 15 or fewer sites,we demonstrate the weak finite-size dependence of spinon velocity for any magnitude of coupling strength Jz and the strong phase dependence of central charge.This behavior of velocity and central charge in different coupling constants and different phases gives a method to determine phase transitions of (1 1)-dimensional models.This method is simple and efficient by utilizing only the ground state energy of very short finite-size chains.It is also general and powerfur for various one-dimensional lattice models and it uncovers eventhe weakest berezinski-Kosterlitz-Thouless phase transitions.     

First-Principles Calculation for the Electron-Phonon Coupling Constant of Superconducting MgB2

We use a first-principles plane wave method with the new relativistic analytic pseudopotential of the Hartwigsen,Goedecker and Hurter (HGH) scheme and the pseudopotential of the Troullier-Martins scheme to calculate the eleetron-phonon coupling constant λ of superconducting MgB2. The calculated results show that there is a peak at about 300-350cm^-1 in the eleetron-phonon spectral functional α2F(ω), duo to the coupling of the electrons to the acoustic phonon, and the relativistic effect appears in the high frequencies zone. All the results agree well with the present and previous experimental data,     

Density Dependence of the Mass and Decay Constant of Pion in Nuclear Matter in the Dyson-Schwinger Equation Approach of QCD

With the Dyson-Schwinger equation formalism at finite chemical potential, we study the density dependence of the mass and decay constant of pion in nuclear matter. The calculated results indicate that both the mass and the decay constant remain almost constant at small chemical potential. As the chemical potential gets quite large, the decay constant increases and the mass decreases with the increasing of the chemical potential, and both of them vanish suddenly as a critical value is reached.     

Determination of the Spin–Spin Coupling Constant in Hydrogen Deuteride HD and Estimates of the Manifestation of Axion-Like Particles

An experimental value of the spin–spin coupling constant in deuterated molecular hydrogen HD has been obtained, J _pd = (43.112 ± 0.005) Hz (300 K), while investigating two gaseous samples at pressures of 95 and 155 atm. The experimental result does not coincide with Jpd = (43.31 ± 0.05) Hz that was calculated theoretically by Helkager et al. The observed discrepancy ΔJ _pd ≈ (0.20 ± 0.05 Hz) may point to a manifestation of the involvement of light pseudo-scalar (axion-like) bosons with a mass m _a ≈ 1 keV/c² in the spin–spin coupling of the HD proton and deuteron.     

Contributions of γd → πNN + π0 d channels to the spin asymmetry and the Gerasimov-Drell-Hearn integral for the deuteron

Contributions from the semi-exclusive channels γd → π^± NN + π⁰ d and γd → π⁰ X (X=pn or d) to the deuteron spin asymmetry and the Gerasimov-Drell-Hearn (GDH) integral are explicitly evaluated using an enhanced elementary pion photoproduction operator and a realistic, high-precision potential model for the deuteron wave function. The sensitivity of the results to the elementary pion photoproduction operator is also investigated and considerable dependence is found. Results for the deuteron GDH integral are compared with the measurements from A2 and GDH@MAMI Collaborations.     

Signature of the ηNN configurations in coherent πphotoproduction on the deuteron

The photoproduction of a neutral pion on the deuteron is considered in the energy region around the η threshold, where a bump-like structure was observed at very backward pion angles. Different dynamical aspects which may be responsible for this phenomenon are analysed within a theoretical frame which includes intermediate ηNN configurations. The results show, in particular, that a three-body treatment of the ηNN interaction is of special importance.     

Joint Effect of the Dipole–Dipole Interaction and Constant Dipole Moment on the Shape of the Field Pulse without an Envelope

Journal of Experimental and Theoretical Physics - An integrable model is proposed for a two-level medium with a constant dipole moment, which describes the evolution of electromagnetic field pulses...     

Semiclassical Models for Virtual Antiparticle Pairs, the Unit of Charge e, and the QCD Coupling α s

New semiclassical models of virtual antiparticle pairs are used to compute the pair lifetimes, and good agreement with the Heisenberg lifetimes from quantum field theory (QFT) is found. The modeling method applies to both the electromagnetic and color forces. Evaluation of the action integral of potential field fluctuation for each interaction potential yields /2 for both electromagnetic and color fluctuations, in agreement with QFT. Thus each model is a quantized semiclassical representation for such virtual antiparticle pairs, to good approximation. When the results of the new models and QFT are combined, formulae for e and _s (q) are derived in terms of only and c.     

Dielectric Properties of Nuclear Matter with the ωNN Interaction at High Temperature

Based on the QHD-1 field equation, the dielectric constant of nuclear matter with the ωNN interaction has been obtained in the framework of kinetic theory. Furthermore, the characters and physical background of the dielectric constant at high temperature is analyzed in detail.     

Dependence of the Constant of the Mark‐Houwink Equation under Theta Conditions on the Bulk of Substituents for Hydrocarbon Polymers

The logarithm of the constant K _θ in the Mark‐Houwink equation under theta conditions was found to be proportional to the molar volume of the substituent groups in the case of vinyl‐ and vinylidene‐type hydrocarbon polymers. This simple empirical relation can be used to estimate K _θ for such polymers.     

Charge Density of ^23,24O with Isoscalar-Isovector Coupling Terms

The nonlinear isoscalar-isovector terms which are used to simulate the density dependence of the symmetry energy are considered in the relativistic mean field model. The charge density distributions of ^23,24O are investigated by considering the contribution from the isoscalar-isovector couplings. Contrarily to the uncertainty of the neutron radius of ^208Pb, a considerable uncertainty exists for the charge radii of ^23,24O. The data-to-data correlation between the neutron thickness of ^208Pb and that of ^23,24O is enhanced by the inclusion of the pNN tensor coupling. This enhancement is closely related to the structural factor, the 2s1/2 occupation of the out-layer neutrons.     

Dynamics of Entropy and Nonclassicality Features of the Interaction between a ◇-type Four-Level Atom and a Single-Mode Field in the Presence of Intensity-Dependent Coupling and Kerr Nonlinearity

The interaction between a◇-type four-level atom and a single-mode field in the presence of Kerr medium with intensity-dependent coupling involving multi-photon processes has been studied. Using the generalized(nonlinear)Jaynes–Cummings model, the exact analytical solution of the wave function for the considered system under particular condition, has been obtained when the atom is initially excited to the topmost level and the field is in a coherent state. Some physical properties of the atom-field entangled state such as linear entropy showing the entanglement degree, Mandel parameter, mean photon number and normal squeezing of the resultant state have been calculated. The effects of Kerr medium, detuning and the intensity-dependent coupling on the temporal behavior of the latter mentioned nonclassical properties have been investigated. It is shown that by appropriately choosing the evolved parameters in the interaction process, each of the above nonclassicality features, which are of special interest in quantum optics as well as quantum information processing, can be revealed.     

Analysis of Mode Coupling of Jet Near Field Puslations and Jet–Wing Interaction Noise

Acoustical Physics - Based on the previously developed analytical model of jet–wing interaction noise, we analyze the results of measuring the azimuthal modes of pressure pulsations in the...     

Ground-State Properties of Ca Isotopes and the Density Dependence of the Symmetry Energy

A relativistic mean field model is used to study the ground-state properties of neutron-rich nuclei in Ca isotopes. An additional isoscalar and isovector nonlinear coupling has been introduced in the relativistic mean field model, which could soften the symmetry energy, while keep the agreement with the experimental data. The sensitivity of proton and neutron density distributions and single particle states in Ca isotopes to the additional isoscalarisovector nonlinear coupling term is investigated. We found that the binding energies, the density distributions of single particle levels are strongly correlated with the density dependence of the symmetric energy in nuclear matter.