Effects of the δ meson on the direct Urca processes in neutron stars

In the framework of the relativistic mean field theory, the effects of the δ meson on the direct Urca (DURCA) processes are investigated. In a neutron star, the DURCA processes involving nucleons, Λ and Ξ^- can take place while the process involving the Ξ⁰ can not. With the inclusion of the δ meson, the threshold densities for the DURCA processes become lower. With the δ included, the threshold neutron star mass for the DURCA process among nucleons and electrons becomes smaller while the threshold masses for the processes involving hyperons become larger. When the δ meson is included, the total neutrino emissivity remarkably increases in the density range of 0.32--0.41 fm^-3. The total neutrino luminosity increases with the neutron star mass first and then decreases. The neutrino luminosity gets larger with the inclusion of the δ meson. The cooling of the EXO0748-676 is sensitive to the isovector scalar interaction.     

Effect of Cr doping in the bilayer manganite La1.4Sr1.6Mn2O7

The effect of Cr doping on magnetic and electrical properties in the bilayer manganites La_1.4Sr_1.6(Mn_1−yCr_y)₂O₇ (y=0-0.1) has been investigated. When y≤0.025, Cr doping enhances the three-dimensional magnetic transition temperature T_C and the insulator-metal transition temperature T_IM as well as decreases the peak resistivity at T_IM, and the saturated magnetization decreases slightly. When y≥0.035, T_IM decreases gradually accompanied by the increase of peak resistivity, but T_C remains nearly constant, and the saturated magnetization decreases heavily. In the whole doping region, the two-dimensional magnetic transition temperature T^? monotonously decreases with an increasing of Cr doping level. These results can be explained by considering different magnetic (including ferromagnetic and antiferromagnetic) interactions between Mn ions and Cr ions.     

Fine structure of the isoscalar giant quadrupole resonance in Ca due to Landau damping?

The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in ⁴⁰Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at Ep=200 MeV$E_{\mathrm{p}}=200\text{MeV}$. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for ⁴⁰Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states.     

The effect of density dependent Av18 effective interaction on the ground state properties of heavy closed shell nuclei

The channel-dependent Argonne Av₁₈ effective two-body interactions (CDEI) which are generated through the lowest order constrained variational (LOCV) calculation for asymmetric nuclear matter with the charge-dependent Av₁₈ bare nucleon–nucleon potential are used to calculate the ground state properties of heavy closed shell nuclei such as ⁴⁸Ca, ⁹⁰Zr, ¹²⁰Sn and ²⁰⁸Pb. The harmonic oscillator basis, and the local density approximation (LDA) are applied to create the relative and the center of mass dependent effective two-body potential. We get more binding with respect to the similar calculation with the Reid types potentials. It is tried to omit the LDA and perform full calculation with the Av₁₈CDEI for light nuclei. The results indicate that the LDA works quite well. It is also shown that in case of heavy closed shell nuclei and unlike our previous report with Reid68Day   interaction, the contributions of higher partial waves (J>2$J>2$) are very important for the calculations with Av₁₈ potential and we get reasonable agreement between our calculated binding energies and RMS radii, with those predicated by the others methods, and the experimental data. Finally, the various aspects of channel and density dependent two-body effective interactions are discussed.     

A PSDPF interaction to describe the 1 ?ω intruder states in sd shell nuclei

In the level schemes of sd shell nuclei, there is generally at relatively low excitation energies, coexistence of normal 0 ?ω positive parity states and of intruder 1 ?ω negative parity states. The aim of the present work is to describe these intruder states in the full p-sd-pf model space with a ⁴He core allowing one nucleon jump between the major shells. To construct our PSDPF interaction, we first modified the p-sd and sd-pf cross-monopole terms and then applied a fitting procedure to adjust all PSDPF parameters by comparing an extended set of experimental and calculated excitation energies. Results obtained with the new interaction have been finally compared with experimental data for nuclei throughout the sd shell.     

Electromagnetic interactions in a cluster of cylinders

We present a rigorous multiple-scattering method to calculate the interaction energies due to electromagnetic field fluctuations in a cluster of parallel cylinders. Various kinds of cluster structure with both isotropic and anisotropic materials are considered. It is shown that Casimir interactions are sensitive to the positions of the cylinders in the cluster or the structure of the system. The sign of the interaction energy cannot only be changed by tuning the parameters of anisotropic materials, it can also be caused by changing the cylinders configuration of the system.     

Existence of global weak solutions for a phase–field model of a vesicle moving into a viscous incompressible fluid

We consider in this article a model of vesicle moving into a viscous incompressible fluid. The vesicle is described through a phase–field equation and through a transport equation modeling the local incompressibility of its membrane. The equations for the fluid are the classical Navier–Stokes equations with a force resulting from the presence of the vesicle. Our main result states the existence of weak solutions for the corresponding system. The proof is based on compactness/monotonicity arguments. Copyright © 2013 John Wiley & Sons, Ltd.     

Bright-soliton collisions with shape change by intensity redistribution for the coupled Sasa–Satsuma system in the optical fiber communications

By means of symbolic computation and Darboux transformation, analytically and numerically investigated in this paper is a two-coupled Sasa–Satsuma system, which can describe the pulse propagation in birefringent fibers, so as to increase the bit rate in optical fibers, or achieve wavelength-division multiplexing. Analytical bright N-soliton solution of the system is firstly derived. Based on the bright one- and two-soliton solutions, numerical simulation and figure illustration are carried out on through the multi-parametric management, i.e., different choices among eight parameters in the two-soliton solutions. The interaction mechanisms for the bright two-solitons are revealed in three aspects: Separating evolution behaviors, elastic collision behaviors and inelastic collision behaviors. There exist three different cases for the inelastic collision for the two-soliton, which reflect correspondingly different energy transfer mechanisms (by intensity redistribution) between the two components: Manakov-typed collision; a near-elastic collision and another completely inelastic collision between the two components; and four single-solitons in two components undergo shape changes (inelastic and elastic) due to intensity redistribution, where one single-soliton keeps invariant and the other three single-solitons change during the collision. The collision mechanisms may be viewed as the two-solitons interact in a waveguide supporting propagation of two nonlinear waves simultaneously. In general, partial suppression (enhancement) of intensity between the components is dependent on the values of the soliton parameters.