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F. Daolio M. Tomassini K. Bitkov 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(3-4):349-359
We study the networks formed by the directors of the most important Swiss boards and the boards themselves for the year 2009. The networks are obtained by projection from the original bipartite graph. We highlight a number of important statistical features of those networks such as degree distribution, weight distribution, and several centrality measures as well as their interrelationships. While similar statistics were already known for other board systems, and are comparable here, we have extended the study with a careful investigation of director and board centrality, a k-core analysis, and a simulation of the speed of information propagation and its relationships with the topological aspects of the network such as clustering and link weight and betweenness. The overall picture that emerges is one in which the topological structure of the Swiss board and director networks has evolved in such a way that special actors and links between actors play a fundamental role in the flow of information among distant parts of the network. This is shown in particular by the centrality measures and by the simulation of a simple epidemic process on the directors network. 相似文献
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We show that, if X is a Stein manifold and D ? X an open set (not necessarily Stein) such that the restriction map has dense image, then, for any reflexive coherent analytic sheaf ℱ on X, the map has dense image, too.
We also characterize the reflexivity of a torsion-free coherent sheaf on complex manifolds in terms of absolute gap sheaves
or Kontinuit?tssatz.
Received: 14 September 2001 / Revised version: 29 January 2002 相似文献
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A. Amore Bonapasta C. Battistoni A. Lapiccirella E. Semprini F. Stefani N. Tomassini 《Il Nuovo Cimento D》1987,9(2):156-162
Summary It has been computed the potential-energy curve ofπ
2 SiH, as a function of the silicon hydrogen bond distance, by means ofab initio HFR-MO-LCAD-SCF-CI method. It has been investigated, in particular, the influence of different basis sets on the computed
structural and vibrational properties of above-quoted molecule.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
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We construct examples of symplectic half-flat manifolds on compact quotients of solvable Lie groups. We prove that the Calabi-Yau
structures are not rigid in the class of symplectic half-flat structures. Moreover, we provide an example of a compact 6-dimensional
symplectic half-flat manifold whose real part of the complex volume form is d-exact. Finally we discuss the 4-dimensional case.
This work was supported by the Projects M.I.U.R. “Geometric Properties of Real and Complex Manifolds”, “Riemannian Metrics
and Differentiable Manifolds” and by G.N.S.A.G.A. of I.N.d.A.M. 相似文献
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We study the metric aspect of the Moyal plane from Connes’ noncommutative geometry point of view. First, we compute Connes’ spectral distance associated with the natural isometric action of ${\mathbb{R}^2}$ R 2 on the algebra of the Moyal plane ${\mathcal{A}}$ A . We show that the distance between any state of ${\mathcal{A}}$ A and any of its translated states is precisely the amplitude of the translation. As a consequence, we obtain the spectral distance between coherent states of the quantum harmonic oscillator as the Euclidean distance on the plane. We investigate the classical limit, showing that the set of coherent states equipped with Connes’ spectral distance tends towards the Euclidean plane as the parameter of deformation goes to zero. The extension of these results to the action of the symplectic group is also discussed, with particular emphasis on the orbits of coherent states under rotations. Second, we compute the spectral distance in the double Moyal plane, intended as the product of (the minimal unitization of) ${\mathcal{A}}$ A by ${\mathbb{C}^2}$ C 2 . We show that on the set of states obtained by translation of an arbitrary state of ${\mathcal{A}}$ A , this distance is given by the Pythagoras theorem. On the way, we prove some Pythagoras inequalities for the product of arbitrary unital and non-degenerate spectral triples. Applied to the Doplicher- Fredenhagen-Roberts model of quantum spacetime [DFR], these two theorems show that Connes’ spectral distance and the DFR quantum length coincide on the set of states of optimal localization. 相似文献