Study of gravitational radiation from cosmic domain walls

In this paper, following the previous study, we evaluate the spectrum of gravitational wave background generated by domain walls which are produced if some discrete symmetry is spontaneously broken in the early universe. We apply two different methods to calculate the gravitational wave spectrum: One is to calculate the gravitational wave spectrum directly from numerical simulations, and another is to calculate it indirectly by estimating the unequal time anisotropic stress power spectrum of the scalar field. Both analysises indicate that the slope of the spectrum changes at two characteristic frequencies corresponding to the Hubble radius at the decay of domain walls and the width of domain walls, and that the spectrum between these two characteristic frequencies becomes flat or slightly red tilted. The second method enables us to evaluate the GW spectrum semi-analytically for the frequencies which can not be resolved in the finite box lattice simulations, but relies on the assumptions for the unequal time correlations of the source.Comment: 17 pages, 9 figures; revised version of the manuscript, accepted for publication in JCA

Separation of Low Reynolds Number Flows Around a Corner

It was shown experimentally that low Reynolds number flows around a sharp corner do not separate at the corner, and separation points move downstream from the corner with decrease in Reynolds number. For the flow in a channel with a backward-facing step, the experimental results showed a good agreement with those of numerical calculation for the position of separation points and the length of standing vortices

Evaluation of Trapped Magnetic Field Properties in Superconducting MgB2_2 Bulk Magnets of Various Shapes by Finite Element Method

The trapped magnetic field properties of superconducting MgB2 bulk magnets with various shapes such as a triangular, a quadrangular, a hexangular bulk were calculated by the Finite Elements Method (FEM). The effect for the combination of several numbers of bulks was also investigated for several kinds of shapes to obtain large area of bulk surface in spite of one large bulk. In this calculation, the simple magnetization process replaced by the field-cool magnetization was used to obtain the equivalent distribution of the magnetic field, and the thermal equation in FEM was omitted. The trapped magnetic field for the triangular bulk by FEM was compared with the experimental result. It was found that the calculated results agreed well with the experimental result. The maximum trapped magnetic field was obtained in the cylindrical shape among several kinds of shapes. The trapped magnetic field was increased by the combination of multi-bulks. It was confirmed that the trapped magnetic field of the multi-bulks was larger than that of the single bulk. The trapped magnetic field increases with increasing the number of the bulks.28th International Symposium on Superconductivity(ISS 2015), November 16-18, 2015, Tokyo, Japa

Co-rich decagonal Al-Co-Ni: predicting structure, orientational order, and puckering

We apply systematic methods previously used by Mihalkovic et al. to predict the structure of the `basic' Co-rich modification of the decagonal Al70 Co20 Ni10 layered quasicrystal, based on known lattice constants and previously calculated pair potentials. The modelling is based on Penrose tile decoration and uses Monte Carlo annealing to discover the dominant motifs, which are converted into rules for another level of description. The result is a network of edge-sharing large decagons on a binary tiling of edge 10.5 A. A detailed analysis is given of the instability of a four-layer structure towards $c$-doubling and puckering of the atoms out of the layers, which is applied to explain the (pentagonal) orientational order.Comment: IOP LaTex; 7 pp, 2 figures. In press, Phil. Mag. A (Proc. Intl. Conf. on Quasicrystals 9, Ames Iowa, May 2005

Novel reconstruction technique for New Physics processes with initial state radiation

At hadron colliders, the production of heavy new particles is associated with additional quarks and gluons with significant transeverse momentum. The additional jets complicates the reconstruction of new particle masses. Taking gluino pair production and decay at the Large Hadron Collider as an example, we develop a novel technique to reduce these effects, and to reconstruct a clear kinematical endpoint for the gluino decay products.Comment: 4 pages, 5 figure