26,040 research outputs found

    Inhomogeneous substructures hidden in random networks

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    We study the structure of the load-based spanning tree (LST) that carries the maximum weight of the Erdos-Renyi (ER) random network. The weight of an edge is given by the edge-betweenness centrality, the effective number of shortest paths through the edge. We find that the LSTs present very inhomogeneous structures in contrast to the homogeneous structures of the original networks. Moreover, it turns out that the structure of the LST changes dramatically as the edge density of an ER network increases, from scale free with a cutoff, scale free, to a starlike topology. These would not be possible if the weights are randomly distributed, which implies that topology of the shortest path is correlated in spite of the homogeneous topology of the random network.Comment: 4 pages, 4 figure

    Varying Cu-Ti hybridization near the Fermi energy in Cux_{x}TiSe2_{2}: Results from supercell calculations

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    The properties of Cux_{x}TiSe2_{2} are studied by band structure calculation based on the density functional theory for supercells. The density-of-states (DOS) for xx=0 has a sharply raising shoulder in the neighborhood of the Fermi energy, EFE_F, which can be favorable for spacial charge modulations. The Cu impurity adds electrons and brings the DOS shoulder below EFE_F. Hybridization makes the Ti-d DOS at EFE_F, the electron-phonon coupling and the Stoner factor very large. Strong pressure dependent properties are predicted from the calculations, since the DOS shoulder is pushed to higher energy at a reduced lattice constant. Effects of disorder are also expected to be important because of the rapidly varying DOS near EFE_F.Comment: 5 pages, 4 figures 2 table

    Quantum Dot and Hole Formation in Sputter Erosion

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    Recently it was experimentally demonstrated that sputtering under normal incidence leads to the formation of spatially ordered uniform nanoscale islands or holes. Here we show that these nanostructures have inherently nonlinear origin, first appearing when the nonlinear terms start to dominate the surface dynamics. Depending on the sign of the nonlinear terms, determined by the shape of the collision cascade, the surface can develop regular islands or holes with identical dynamical features, and while the size of these nanostructures is independent of flux and temperature, it can be modified by tuning the ion energy
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