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Jun 30, 2018
06/18

by
Filippo Radicchi

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We consider different methods, that do not rely on numerical simulations of the percolation process, to approximate percolation thresholds in networks. We perform a systematic analysis on synthetic graphs and a collection of 109 real networks to quantify their effectiveness and reliability as prediction tools. Our study reveals that the inverse of the largest eigenvalue of the non-backtracking matrix of the graph often provides a tight lower bound for true percolation threshold. However, in...

Topics: Physics, Physics and Society, Statistical Mechanics, Condensed Matter

Source: http://arxiv.org/abs/1412.3678

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Jun 27, 2018
06/18

by
Filippo Radicchi

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The function of a real network depends not only on the reliability of its own components, but is affected also by the simultaneous operation of other real networks coupled with it. Robustness of systems composed of interdependent network layers has been extensively studied in recent years. However, the theoretical frameworks developed so far apply only to special models in the limit of infinite sizes. These methods are therefore of little help in practical contexts, given that real...

Topics: Condensed Matter, Statistical Mechanics, Physics and Society, Physics

Source: http://arxiv.org/abs/1503.04655

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Jun 30, 2018
06/18

by
Filippo Radicchi

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Power-law distributions are typical macroscopic features occurring in almost all complex systems observable in nature. As a result, researchers in quantitative analyses must often generate random synthetic variates obeying power-law distributions. The task is usually performed through standard methods that map uniform random variates into the desired probability space. Whereas all these algorithms are theoretically solid, in this paper we show that they are subject to severe machine-dependent...

Topics: Physics, Computation, Statistics, Statistical Mechanics, Physics and Society, Condensed Matter

Source: http://arxiv.org/abs/1405.0058

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Jun 29, 2018
06/18

by
Filippo Radicchi; Claudio Castellano

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The stochastic addition of either vertices or connections in a network leads to the observation of the percolation transition, a structural change with the appearance of a connected component encompassing a finite fraction of the system. Percolation has always been regarded as a substrate-dependent but model-independent process, in the sense that the critical exponents of the transition are determined by the geometry of the system, but they are identical for the bond and site percolation...

Topics: Statistical Mechanics, Condensed Matter, Physics, Physics and Society

Source: http://arxiv.org/abs/1606.06933

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Jun 29, 2018
06/18

by
Filippo Radicchi; Claudio Castellano

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Theoretical attempts proposed so far to describe ordinary percolation processes on real-world networks rely on the locally tree-like ansatz. Such an approximation, however, holds only to a limited extent, as real graphs are often characterized by high frequencies of short loops. We present here a theoretical framework able to overcome such a limitation for the case of site percolation. Our method is based on a message passing algorithm that discounts redundant paths along triangles in the...

Topics: Statistical Mechanics, Condensed Matter, Physics, Physics and Society

Source: http://arxiv.org/abs/1602.07140

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Jun 29, 2018
06/18

by
Filippo Radicchi; Ginestra Bianconi

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In the analysis of the robustness of multiplex networks, it is commonly assumed that a node is functioning only if its interdependent nodes are simultaneously functioning. According to this model, a multiplex network becomes more and more fragile as the number of layers increases. In this respect, the addition of a new layer of interdependent nodes to a preexisting multiplex network will never improve its robustness. Whereas such a model seems appropriate to understand the effect of...

Topics: Statistical Mechanics, Condensed Matter, Physics, Physics and Society

Source: http://arxiv.org/abs/1610.05378

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Jun 30, 2018
06/18

by
Saeed Osat; Filippo Radicchi

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We extend the observability model to multiplex networks. We present mathematical frameworks, valid under the treelike ansatz, able to describe the emergence of the macroscopic cluster of mutually observable nodes in both synthetic and real-world multiplex networks. We show that the observability transition in synthetic multiplex networks is discontinuous. In real-world multiplex networks instead, edge overlap among layers is responsible for the disappearance of any sign of abruptness in the...

Topics: Physics, Computing Research Repository, Physics and Society, Social and Information Networks

Source: http://arxiv.org/abs/1701.04042

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Jun 29, 2018
06/18

by
Ginestra Bianconi; Filippo Radicchi

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We present an exact mathematical framework able to describe site-percolation transitions in real multiplex networks. Specifically, we consider the average percolation diagram valid over an infinite number of random configurations where nodes are present in the system with given probability. The approach relies on the locally treelike ansatz, so that it is expected to accurately reproduce the true percolation diagram of sparse multiplex networks with negligible number of short loops. The...

Topics: Statistical Mechanics, Condensed Matter, Physics, Physics and Society

Source: http://arxiv.org/abs/1610.08708

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3.0

Jun 30, 2018
06/18

by
Filippo Radicchi; Claudio Castellano

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Many real-world systems are characterized by stochastic dynamical rules where a complex network of dependencies among individual elements probabilistically determines their state. Even with full knowledge of the network structure and of the stochastic rules of the dynamical process, the ability to predict system configurations is generally characterized by large uncertainty. Sampling a fraction of the nodes and deterministically observing their state may help to reduce the uncertainty about the...

Topics: Physics, Information Theory, Computing Research Repository, Physics and Society, Mathematics

Source: http://arxiv.org/abs/1703.03858

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Jun 29, 2018
06/18

by
Yang Yang; Filippo Radicchi

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We consider the observability model in networks with arbitrary topologies. We introduce a system of coupled nonlinear equations, valid under the locally tree-like ansatz, to describe the size of the largest observable cluster as a function of the fraction of directly observable nodes present in the network. We perform a systematic analysis on 95 real-world graphs and compare our theoretical predictions with numerical simulations of the observability model. Our method provides almost perfect...

Topics: Physics and Society, Statistical Mechanics, Condensed Matter, Physics, Computing Research...

Source: http://arxiv.org/abs/1607.07124

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Jun 29, 2018
06/18

by
Filippo Radicchi; Claudio Castellano

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Two very important problems regarding spreading phenomena in complex topologies are the optimal selection of node sets either to minimize or maximize the extent of outbreaks. Both problems are nontrivial when a small fraction of the nodes in the network can be used to achieve the desired goal. The minimization problem is equivalent to a structural optimization. The "superblockers", i.e., the nodes that should be removed from the network to minimize the size of outbreaks, are those...

Topics: Social and Information Networks, Computing Research Repository, Physics, Physics and Society

Source: http://arxiv.org/abs/1610.02908

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Jun 29, 2018
06/18

by
Filippo Radicchi; Claudio Castellano

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Among the consequences of the disordered interaction topology underlying many social, techno- logical and biological systems, a particularly important one is that some nodes, just because of their position in the network, may have a disproportionate effect on dynamical processes mediated by the complex interaction pattern. For example, the early adoption by an opinion leader in a social network may change the fate of a commercial product, or just a few super-spreaders may determine the virality...

Topics: Social and Information Networks, Computing Research Repository, Physics, Physics and Society

Source: http://arxiv.org/abs/1605.07041

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Jun 29, 2018
06/18

by
Filippo Radicchi; Alexander Weissman; Johan Bollen

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Citations are commonly held to represent scientific impact. To date, however, there is no empirical evidence in support of this postulate that is central to research assessment exercises and Science of Science studies. Here, we report on the first empirical verification of the degree to which citation numbers represent scientific impact as it is actually perceived by experts in their respective field. We run a large-scale survey of about 2000 corresponding authors who performed a pairwise...

Topics: Physics, Digital Libraries, Computing Research Repository, Physics and Society

Source: http://arxiv.org/abs/1612.03962

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Jun 30, 2018
06/18

by
Jasleen Kaur; Emilio Ferrara; Filippo Menczer; Alessandro Flammini; Filippo Radicchi

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Citation metrics are becoming pervasive in the quantitative evaluation of scholars, journals and institutions. More then ever before, hiring, promotion, and funding decisions rely on a variety of impact metrics that cannot disentangle quality from quantity of scientific output, and are biased by factors such as discipline and academic age. Biases affecting the evaluation of single papers are compounded when one aggregates citation-based metrics across an entire publication record. It is not...

Topics: Digital Libraries, Physics, Computing Research Repository, Physics and Society

Source: http://arxiv.org/abs/1411.7357

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Jun 27, 2018
06/18

by
Qing Ke; Emilio Ferrara; Filippo Radicchi; Alessandro Flammini

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A Sleeping Beauty (SB) in science refers to a paper whose importance is not recognized for several years after publication. Its citation history exhibits a long hibernation period followed by a sudden spike of popularity. Previous studies suggest a relative scarcity of SBs. The reliability of this conclusion is, however, heavily dependent on identification methods based on arbitrary threshold parameters for sleeping time and number of citations, applied to small or monodisciplinary...

Topics: Social and Information Networks, Physics and Society, Digital Libraries, Computing Research...

Source: http://arxiv.org/abs/1505.06454