In the multidisciplinary field of Network Science, optimization of procedures for efficiently breaking complex networks is attracting much attention from a practical point of view. In this ...contribution, we present a module-based method to efficiently fragment complex networks. The procedure firstly identifies topological communities through which the network can be represented using a well established heuristic algorithm of community finding. Then only the nodes that participate of inter-community links are removed in descending order of their betweenness centrality. We illustrate the method by applying it to a variety of examples in the social, infrastructure, and biological fields. It is shown that the module-based approach always outperforms targeted attacks to vertices based on node degree or betweenness centrality rankings, with gains in efficiency strongly related to the modularity of the network. Remarkably, in the US power grid case, by deleting 3% of the nodes, the proposed method breaks the original network in fragments which are twenty times smaller in size than the fragments left by betweenness-based attack.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Recent research has shown that criminal networks have complex organizational structures, but whether this can be used to predict static and dynamic properties of criminal networks remains ...little explored. Here, by combining graph representation learning and machine learning methods, we show that structural properties of political corruption, police intelligence, and money laundering networks can be used to recover missing criminal partnerships, distinguish among different types of criminal and legal associations, as well as predict the total amount of money exchanged among criminal agents, all with outstanding accuracy. We also show that our approach can anticipate future criminal associations during the dynamic growth of corruption networks with significant accuracy. Thus, similar to evidence found at crime scenes, we conclude that structural patterns of criminal networks carry crucial information about illegal activities, which allows machine learning methods to predict missing information and even anticipate future criminal behavior.
This paper assesses the distributional effects of carbon pricing on Brazilian households. We apply a multi-regional Computable General Equilibrium (CGE) model with representation of multiple ...households according to a family expenditure survey. Important questions for policy makers in Brazil are addressed. What are the economic effects of introducing carbon pricing in Brazil? Is there a double dividend, with economic and environmental benefits, when carbon revenue is recycled through tax rebates? Could carbon revenue contribute to the financing of social spending and to income distribution improvements in Brazil? Results show that carbon pricing avoids further carbon intensive infrastructure lock-in by further promoting biomass in electricity generation and biofuels in the transportation sector. Lump-sum transfers from carbon revenue help boosting income of lower deciles up to +4.5%, while targeting transfers to most vulnerable groups leads to an income growth of +42.2% by 2030. Brazil has a large gap in terms of effective carbon pricing when compared to other countries that could be addressed in the context of the ongoing tax reform debate, with carbon revenue contributing to the financing of social spending. Our analysis examines different policy design options and contribute to the debate about fiscal reform and socioeconomic effects of carbon pricing in Brazil.
•Carbon pricing could finance social spending by adding nearly USD 140 to households' budget under the extreme poverty line.•Source-side impacts prevail, leading to progressive effects in lump-sum scenarios.•Welfare gains are restricted to a few low-income deciles and suggest a double dividend in its weak form.•Moderate GDP growth is found for Brazil, mainly driven by trade effects, due to worldwide carbon pricing.
Scalar quasinormal modes of Kerr−AdS5 Amado, Julián Barragán; da Cunha, Bruno Carneiro; Pallante, Elisabetta
Physical review. D,
05/2019, Letnik:
99, Številka:
10
Journal Article
Recenzirano
An analytic expression for the scalar quasinormal modes of generic, spinning Kerr−AdS5 black holes was previously proposed by the authors J. High Energy Phys. 08 (2017) 094, in terms of ...transcendental equations involving the Painlevé VI (PVI) τ function. In this work, we carry out a numerical investigation of the modes for generic rotation parameters, comparing implementations of expansions for the PVI τ function in terms of both conformal blocks (Nekrasov functions) and Fredholm determinants. We compare the results with standard numerical methods for the subcase of Schwarzschild black holes. We then derive asymptotic formulas for the angular eigenvalues and the quasinormal modes in the small black hole limit for generic scalar mass and discuss, both numerically and analytically, the appearance of superradiant modes.
Cost minimization is arguably the most important criterion governing decisions about energy sector infrastructure construction. Usually, a winning project is picked among similar alternatives based ...on lowest levelized cost of energy, because, ceteris paribus, economies of scale drive down the unit cost of energy delivered. As such, megaprojects – here defined as costing more than a benchmark US$ 1 billion – are perceived as more competitive than smaller-scale options. However, megaprojects are prone to construction cost overruns and delays that, if included ex ante, may change the optimality of decision for a given project. We hypothesize that optimistic assumptions on techno-economic performance of megaprojects favor their inclusion in the solution of integrated assessment models (IAMs), preventing higher shares of non-hydro renewables, energy efficiency and other low-carbon options. To test this hypothesis, we ran the COPPE-MSB energy system cost-optimization model for infrastructure expansion. We estimate a factor (named Z factor, for zillions) to determine cost differences both within Brazil and vis-à-vis international parity and adjust the model's parameters for CAPEX and construction times of projects qualifying as megaprojects. Results show decreased coal and increased wind power generation, and a reduction in the number of new refineries leading to higher imports of diesel and gasoline.
•Literature review of empirical megaproject cost overrun and construction delays (power and O&G).•Index proposed to assess inter-regional capex cost differences of energy projects named Z-Factor.•Z-Factors implemented in energy system model to assess impact of cost overruns and delays in Brazil.•Result: delays and cost overruns impact Brazil energy security, increase oil products imports.•Non-hydro renewables fill the gap, indicating they should be the preferred option ex-ante.
A
bstract
We study the low-temperature limit of scalar perturbations of the Kerr-AdS
5
black-hole for generic rotational parameters. We motivate the study by considering real-time holography of small ...black hole backgrounds. Using the isomonodromic technique, we show that corrections to the extremal limit can be encoded in the monodromy parameters of the Painlevé V transcendent, whose expansion is given in terms of irregular chiral conformal blocks. After discussing the contribution of the intermediate states to the quasinormal modes, we perform a numerical analysis of the low-lying frequencies. We find that the fundamental mode is perturbatively stable at low temperatures for small black holes and that excited perturbations are superradiant, as expected from thermodynamical considerations. We close by considering the holographic interpretation of the unstable modes and the decaying process.
A
bstract
We analyze the Ansatz of separability for Maxwell equations in generically spinning, five-dimensional Kerr-AdS black holes. We find that the parameter
μ
introduced in 1 can be interpreted ...as apparent singularities of the resulting radial and angular equations. Using isomonodromy deformations, we describe a non-linear symmetry of the system, under which
μ
is tied to the Painlevé VI transcendent. By translating the boundary conditions imposed on the solutions of the equations for quasinormal modes in terms of monodromy data, we find a procedure to fix
μ
and study the behavior of the quasinormal modes in the limit of fast spinning small black holes.
The contamination of coastal environments by metallurgical wastes involves multiple biogeochemical processes; accordingly, understanding metal behavior and risk evaluation of contaminated areas, such ...as Sepetiba Bay (Rio de Janeiro, Brazil), remains challenging. This study coupled Zn isotopic analyses with sequential extractions (BCR) to investigate the mechanisms of Zn transfer between legacy electroplating waste and the main environments in Sepetiba Bay. This metallurgical waste showed a light bulk isotopic signature (δ66/64ZnbulkJMC = +0.30 ± 0.01‰, 2 s, n = 3) that was not distinct from the lithogenic geochemical baseline, but was different from signature of mangrove sediment considered as anthropogenic end member (δ66/64ZnJMC = +0.86 ± 0.15‰) in a previous isotopic study in this area. Zn isotopic compositions of sediment samples (ranging from +0.20 to +0.98‰) throughout the bay fit a mixing model involving multiple sources, consistent with previous studies. In the metallurgic zone, the exchangeable/carbonate fraction (ZnF1) exhibited high Zn concentrations (ZnF1 = 9840 μg g−1) and a heavy isotopic composition (δ66/64ZnF1JMC = +1.10 ± 0.01‰). This finding showed that, in some cases, the bulk isotopic signature of waste is not the most relevant criterion for evaluating trace metal dispersion in the environment. Indeed, based on the BCR, it was observed that part of the anthropogenic metallurgical Zn was redistributed from the exchangeable/carbonate fraction in the waste to the surrounding mangrove sediment. Then, this contaminated sediment with heavy δ66/64Zn values was exported to other coastal environments. In Sepetiba Bay, contaminated sediments revealed a large concentration of ZnF1 fraction (up to 400 μg g−1) with a heavy Zn isotopic signature. This signature also matched the Zn isotopic signature of oysters in Sepetiba Bay reported by other studies; hence, measurement of the isotopic exchangeable/carbonate fraction has important implications for tracing the transfer of anthropogenic Zn to biota.
Display omitted
•Anthropogenic Zn biogeochemistry in aquatic systems is complex.•Zn redistribution from electroplating wastes in mangrove sediment was investigated.•Geochemical processes in the mangrove promoted Zn isotope redistribution.•Isotope data allowed tracing transfer of anthropogenic Zn from waste to biota.•Most of anthropogenic Zn occurs in sediment as exchangeable/carbonates.
A
bstract
We study the scattering of a massless scalar field in a generic Kerr background. Using a particular gauge choice based on the current conservation of the radial equation, we give a generic ...formula for the scattering coefficient in terms of the composite monodromy parameter
σ
between the inner and the outer horizons. Using the isomonodromy flow, we calculate
σ
exactly in terms of the Painlevé V
τ
-function. We also show that the eigenvalue problem for the angular equation (spheroidal harmonics) can be calculated using the same techniques. We use recent developments relating the Painlevé V
τ
-function to Liouville irregular conformal blocks to claim that this scattering problem is solved in the combinatorial sense, with known expressions for the
τ
-function near the critical points.
Corruption crimes demand highly coordinated actions among criminal agents to succeed. But research dedicated to corruption networks is still in its infancy and indeed little is known about the ...properties of these networks. Here we present a comprehensive investigation of corruption networks related to political scandals in Spain and Brazil over nearly three decades. We show that corruption networks of both countries share universal structural and dynamical properties, including similar degree distributions, clustering and assortativity coefficients, modular structure, and a growth process that is marked by the coalescence of network components due to a few recidivist criminals. We propose a simple model that not only reproduces these empirical properties but reveals also that corruption networks operate near a critical recidivism rate below which the network is entirely fragmented and above which it is overly connected. Our research thus indicates that actions focused on decreasing corruption recidivism may substantially mitigate this type of organized crime.
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