Relation between the separable and one-boson-exchange potential for the covariant Bethe-Salpeter equation

We investigate the relation between the rank I separable potential for the covariant Bethe-Salpeter equation and the one-boson-exchange potential. After several trials of the parameter choices, it turns out that it is not always possible to reproduce the phase-shifts calculated from a single term of the one-boson-exchange potential especially of the $\sigma$-exchange term, separately by the rank I separable potential. Instead, it is shown that the separable potential is useful to parameterize the total nucleon-nucleon interaction.Comment: 10 pages, 8 figures, to appear in J.Phys.

Search for long-lived massive particles in extensive air showers

Air showers containing delayed sub-showers which may be produced by a long-lived massive particle have been investigated by using twelve detectors. Ten events have been selected out as the candidates. However, a definite conclusion cannot be reached at the present time

Magnetic-field effects on the in-plane electrical resistivity in the single-crystal La2−x_{2-x}Bax_xCuO4_4 and La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_xCuO4_4 around x=1/8x=1/8: Relating to the field-induced stripe order

Temperature dependence of the in-plane electrical resistivity, $\rho_{\rm ab}$, in various magnetic fields has been measured in the single-crystal La$_{2-x}$Ba$_x$CuO$_4$ with $x=0.08$, 0.10, 0.11 and La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ with $x=0.12$. It has been found that the superconducting transition curve shows a so-called fan-shape broadening in magnetic fields for $x=0.08$, while it shifts toward the low-temperature side in parallel with increasing field for $x=0.11$ and 0.12 where the charge-spin stripe order is formed at low temperatures. As for $x=0.10$, the broadening is observed in low fields and it changes to the parallel shift in high fields above 9 T. Moreover, the normal-state value of $\rho_{\rm ab}$ at low temperatures markedly increases with increasing field up to 15 T. It is possible that these pronounced features of $x=0.10$ are understood in terms of the magnetic-field-induced stabilization of the stripe order suggested from the neutron-scattering measurements in the La-214 system. The $\rho_{\rm ab}$ in the normal state at low temperatures has been found to be proportional to ln(1/$T$) for $x=0.10$, 0.11 and 0.12. The ln(1/$T$) dependence of $\rho_{\rm ab}$ is robust even in the stripe-ordered state.Comment: 6 pages, 4 figures, ver. 2 has been accepted for publication in Phys. Rev.

A novel approach to investigate surface roughness evolution in asymmetric rolling based on three dimensional real surface

Surface roughness affects the friction behaviour, stress distribution and surface quality; moreover this influence is more significant when scaling down the strip size. A novel approach has been proposed to investigate the surface roughness in asymmetric rolling based on Finite Element Analysis (FEA). Evolution of asperity flattening, contact area ratio and surface roughness is investigated under various simulation rolling conditions. The model reviewed numerical solutions for real surfaces with asperities of arbitrary shape and varying size and height distributions. The rolling characterization has also been identified for asymmetric rolling. The difference of change in surface roughness for upper and lower strip surface is large during rolling. The effect of the speed asymmetry factor on strip bending has been established. An increase of the speed asymmetry factor causes an increase in the strip curvature, while the force parameters decrease with increasing asymmetry factor. The speed asymmetric factor influences the strip bending significantly. It is the first attempt to carry out this kind of research in surface roughness based on real surface during asymmetric rolling of thin strip. 2013 Elsevier B.V

Wilson ratio of a Tomonaga-Luttinger liquid in a spin-1/2 Heisenberg ladder

Using micromechanical force magnetometry, we have measured the magnetization of the strong-leg spin-1/2 ladder compound (C$_7$H$_{10}$N)$_2$CuBr$_2$ at temperatures down to 45 mK. Low-temperature magnetic susceptibility as a function of field exhibits a maximum near the critical field H_c at which the magnon gap vanishes, as expected for a gapped one-dimensional antiferromagnet. Above H_c a clear minimum appears in the magnetization as a function of temperature as predicted by theory. In this field region, the susceptibility in conjunction with our specific heat data yields the Wilson ratio R_W. The result supports the relation R_W=4K, where K is the Tomonaga-Luttinger-liquid parameter

Neutron Scattering Study of Temperature-Concentration Phase Diagram of (Cu1-xMgx)GeO3

In doped CuGeO3 systems, such as (Cu1-xZnx)GeO3 and Cu(Ge1-xSix)O3, the spin-Peierls (SP) ordering (T<Tsp) coexists with the antiferromagnetic (AF) phase (T<TN<Tsp). Tsp decreases while TN increases with increasing x in low doping region. For higher x, however, the SP state disappears and only the AF state remains. These features are common for all the doped CuGeO3 systems so far studied, indicating the existence of universal T-x phase diagram. Recently, Masuda et al. carried out comprehensive magnetic susceptibility (chi) measurements of (Cu1-xMgx)GeO3, in which doping concentration can be controlled significantly better than the Zn doped systems. They found that TN suddenly jumps from 3.43 to 3.98K at the critical concentration xc sim 0.023 and that a drop in chi corresponding to the SP ordering also disappears at x>xc. They thus concluded that there is a compositional phase boundary between two distinct magnetic phases. To clarify the nature of two phases, we performed neutron-scattering measurements on (Cu1-xMgx)GeO3 single crystals with various x. Analysis of the data at fixed temperature points as a function of doping concentration has revealed sudden changes of order parameters at the critical concentration xc=0.027 +- 0.001. At finite temperatures below TN, the drastic increase of the AF moment takes place at xc. The spin-Peierls order parameter delta associated with lattice dimerization shows a precipitous decrease at all temperature below Tsp. However, it goes to zero above xc only at the low temperature limit.Comment: 9 pages, 9 figure