3,513 research outputs found

    Rich-club connectivity dominates assortativity and transitivity of complex networks

    Get PDF
    Rich-club, assortativity and clustering coefficients are frequently-used measures to estimate topological properties of complex networks. Here we find that the connectivity among a very small portion of the richest nodes can dominate the assortativity and clustering coefficients of a large network, which reveals that the rich-club connectivity is leveraged throughout the network. Our study suggests that more attention should be payed to the organization pattern of rich nodes, for the structure of a complex system as a whole is determined by the associations between the most influential individuals. Moreover, by manipulating the connectivity pattern in a very small rich-club, it is sufficient to produce a network with desired assortativity or transitivity. Conversely, our findings offer a simple explanation for the observed assortativity and transitivity in many real world networks --- such biases can be explained by the connectivities among the richest nodes.Comment: 5 pages, 2 figures, accepted by Phys. Rev.

    A Simple Method to Measure the Interaction Potential of Dielectric Grains in a Dusty Plasma

    Full text link
    A simple minimally perturbative method is introduced which provides the ability to experimentally measure both the radial confining potential and the interaction potential between two individual dust particles, levitated in the sheath of a radio-frequency (RF) argon discharge. In this technique, a single dust particle is dropped into the plasma sheath to interact with a second individual dust particle already situated at the system's equilibrium point, without introducing any external perturbation. The resulting data is analyzed using a method employing a polynomial fit to the particle displacement(s), X(t), to reduce uncertainty in calculation. Employing this technique, the horizontal confinement is shown to be parabolic over a wide range of pressures and displacements from the equilibrium point. The interaction potential is also measured and shown to be well-described by a screened Coulomb potential and to decrease with increasing pressure. Finally, the charge on the particle and the effective dust screening distance are calculated. It is shown for the first time experimentally that the charge on a particle in the sheath of an RF plasma decreases with increasing pressure, in agreement with theoretical predictions. The screening distance also decreases with increasing pressure as expected. This technique can be used for rapid determination of particle parameters in dusty plasma

    Direct reconstruction of dynamical dark energy from observational Hubble parameter data

    Full text link
    Reconstructing the evolution history of the dark energy equation of state parameter w(z)w(z) directly from observational data is highly valuable in cosmology, since it contains substantial clues in understanding the nature of the accelerated expansion of the Universe. Many works have focused on reconstructing w(z)w(z) using Type Ia supernova data, however, only a few studies pay attention to Hubble parameter data. In the present work, we explore the merit of Hubble parameter data and make an attempt to reconstruct w(z)w(z) from them through the principle component analysis approach. We find that current Hubble parameter data perform well in reconstructing w(z)w(z); though, when compared to supernova data, the data are scant and their quality is worse. Both Λ\LambdaCDM and evolving w(z)w(z) models can be constrained within 10%10\% at redshifts z1.5z \lesssim 1.5 and even 5%5\% at redshifts 0.1 \lesssim z \lesssim 1 by using simulated H(z)H(z) data of observational quality.Comment: 25 pages, 11 figure
    corecore