18,506 research outputs found

    Index statistical properties of sparse random graphs

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    Using the replica method, we develop an analytical approach to compute the characteristic function for the probability PN(K,λ)\mathcal{P}_N(K,\lambda) that a large N×NN \times N adjacency matrix of sparse random graphs has KK eigenvalues below a threshold λ\lambda. The method allows to determine, in principle, all moments of PN(K,λ)\mathcal{P}_N(K,\lambda), from which the typical sample to sample fluctuations can be fully characterized. For random graph models with localized eigenvectors, we show that the index variance scales linearly with N1N \gg 1 for λ>0|\lambda| > 0, with a model-dependent prefactor that can be exactly calculated. Explicit results are discussed for Erd\"os-R\'enyi and regular random graphs, both exhibiting a prefactor with a non-monotonic behavior as a function of λ\lambda. These results contrast with rotationally invariant random matrices, where the index variance scales only as lnN\ln N, with an universal prefactor that is independent of λ\lambda. Numerical diagonalization results confirm the exactness of our approach and, in addition, strongly support the Gaussian nature of the index fluctuations.Comment: 10 pages, 5 figure

    Transformational government and assistive web base technologies

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    Transformational government has been on the European agenda for several years. However, progress towards realising the full potential of ICT to transform public services for older adults with age related cognitive impairments has been very limited. Highlighting such limitations this paper demonstrates how assistive web base technologies can be developed to improve the public services for older adults with age related cognitive impairments. However the paper argues that these transformations can be obstructed if there is no strong leadership and political commitment from people at many levels in public sectors and governments
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