Wikipedias: Collaborative web-based encyclopedias as complex networks

Wikipedia is a popular web-based encyclopedia edited freely and collaboratively by its users. In this paper we present an analysis of Wikipedias in several languages as complex networks. The hyperlinks pointing from one Wikipedia article to another are treated as directed links while the articles represent the nodes of the network. We show that many network characteristics are common to different language versions of Wikipedia, such as their degree distributions, growth, topology, reciprocity, clustering, assortativity, path lengths and triad significance profiles. These regularities, found in the ensemble of Wikipedias in different languages and of different sizes, point to the existence of a unique growth process. We also compare Wikipedias to other previously studied networks.Comment: v3: 9 pages, 12 figures, Change of title, few paragraphs and two figures. Accepted for publication in Phys. Rev.

Modern Policing, Reform Efforts, and Implementation of Evidence-Based Practices for Eyewitness Identification Procedures

This article discusses various avenues to law enforcement reform that have been proposed, especially in regard to adoption of evidence-based practices. The authors advocate for specific reforms regarding eyewitness identification policies and protocols, and offer an overview of the supporting research. A brief history of the challenges to police reform is presented with an emphasis on how political factors stymie success. The authors assert that expanding use of model policies for eyewitness identification, either through legislation or appealing to agencies to voluntarily adopt such policies, is relatively apolitical and requires minimal to moderate cost and effort

Correctional Reform in Red States: Missouri’s Role

Approximately ten years ago, a conservative-led movement to engage in various forms of correctional and sentencing reform emerged. This movement extends to broader acceptance within the criminal justice field to implement less traditional forms of sentencing, including alternative sentences that incorporate rehabilitative components. A decade later, this policy debate has gained significant traction throughout many conservative states that have traditionally relied upon mass incarceration as the chief means of crime control. Recent scholarly evidence suggests that the reform efforts within these conservative states have met with success in reducing prison populations and the development of rehabilitative strategies increasingly in line with public opinion polls. Moreover, these reforms have brought greater focus to evidence-based practices and increasing attention to empirically-derived evidence of “what works” in reducing recidivism. This paper presents the results of an evaluation of a drug court in a Missouri judicial circuit as an example of how such efforts have spread throughout Missouri. We offer recommendations for policymakers seeking to support this largely bipartisan issue and take advantage of what may be a shrinking window of opportunity

Transport Coefficients of the Anderson Model via the Numerical Renormalization Group

The transport coefficients of the Anderson model are calculated by extending Wilson's NRG method to finite temperature Green's functions. Accurate results for the frequency and temperature dependence of the single--particle spectral densities and transport time $\tau(\omega,T)$ are obtained and used to extract the temperature dependence of the transport coefficients in the strong correlation limit. The low temperature anomalies in the resistivity, $\rho(T)$, thermopower, $S(T)$, thermal conductivity $\kappa(T)$ and Hall coefficient, $R_{H}(T)$, are discussed. All quantities exhibit the expected Fermi liquid behaviour at low temperature with power law dependecies on $T/T_{K}$ in very good agreement with analytic results based on Fermi liquid theory. Scattering of conduction electrons in higher, $l>0$, angular momentum channels is also considered and an expression is derived for the corresponding transport time and used to discuss the influence of non--resonant scattering on the transport properties.Comment: 45 pages, RevTeX, 28 figures, available on reques

Crystal-field effects in the first-order valence transition in YbInCu4 induced by an external magnetic field

As it was shown earlier [Dzero, Gor'kov, and Zvezdin, J. Phys.:Condens. Matter 12, L711 (2000)] the properties of the first-order valence phase transition in YbInCu4 in the wide range of magnetic fields and temperatures are perfectly described in terms of a simple entropy transition for free Yb ions. Within this approach, the crystal field effects have been taken into account and we show that the phase diagram in the $B-T$ plane acquires some anisotropy with respect to the direction of an external magnetic field.Comment: 4 pages, 3 eps figures; minor changes; to be piblished in J. of Physics: Cond. Ma

Critical field-exponents for secure message-passing in modular networks

We study secure message-passing in the presence of multiple adversaries in modular networks. We assume a dominant fraction of nodes in each module have the same vulnerability, i.e., the same entity spying on them. We find both analytically and via simulations that the links between the modules (interlinks) have effects analogous to a magnetic field in a spin-system in that for any amount of interlinks the system no longer undergoes a phase transition. We then define the exponents δ, which relates the order parameter (the size of the giant secure component) at the critical point to the field strength (average number of interlinks per node), and γ, which describes the susceptibility near criticality. These are found to be δ = 2 and γ = 1 (with the scaling of the order parameter near the critical point given by β = 1). When two or more vulnerabilities are equally present in a module we find δ = 1 and γ = 0 (with β ≥ 2). Apart from defining a previously unidentified universality class, these exponents show that increasing connections between modules is more beneficial for security than increasing connections within modules. We also measure the correlation critical exponent ν, and the upper critical dimension d c, finding that as for ordinary percolation, suggesting that for secure message-passing d c = 6. These results provide an interesting analogy between secure message-passing in modular networks and the physics of magnetic spin-systems

The Kondo Dynamics of YbIn(1-x)AgxCu4

We present an infrared/optical study of the dynamics of the strongly correlated electron system YbIn(1-x)AgxCu4 as a function of doping and temperature for x ranging from 0 to 1, and T between 20 and 300 K. This study reveals information about the unusual phase transition as well as the phases themselves. Scaling relations emerge from the data and are investigated in detail using a periodic Anderson model based calculation. We also provide a picture in which to view both the low and high-energy x-dependent features of the infrared data, including identification of high energy, temperature dependent features.Comment: 12 pages, 11 figures, submitted Phys. Rev.

Renormalized Perturbation Approach for Examination of Itinerant-Localized Duality Model for Strongly Correlated Electron Systems

We present a microscopic examination for the itinerant-localized duality model which has been proposed to understand anomalous properties of strongly correlated systems like the heavy fermions by Kuramoto and Miyake, and also useful to describe the anomalous properties of the high-Tc cupurates. We show that the thermodynamic potential of the strongly interacting Hubbard model can be rearranged in the form of duality model on the basis of renormalized perturbation expansion of the Luttinger-Ward functional if the one-particle spectral weight exhibits triple peak structure. We also examine the incoherent degrees of freedom described as a ``localized spin'' and show on the basis of the pertubation expansion that there exists commensurate superexchange-type interaction among the ``localized spins''.Comment: 17 pages, LaTeX, 14 figure PS file, Submitted to J. Phys. Soc. Jp

Finite temperature dynamics of the Anderson model

The recently introduced local moment approach (LMA) is extended to encompass single-particle dynamics and transport properties of the Anderson impurity model at finite-temperature, T. While applicable to arbitrary interaction strengths, primary emphasis is given to the strongly correlated Kondo regime (characterized by the T=0 Kondo scale $\omega_{\rm K}$). In particular the resultant universal scaling behaviour of the single-particle spectrum D(\omega; T) \equiv F(\frac{\w}{\omega_{\rm K}}; \frac{T}{\omega_{\rm K}}) within the LMA is obtained in closed form; leading to an analytical description of the thermal destruction of the Kondo resonance on all energy scales. Transport properties follow directly from a knowledge of $D(\omega; T)$. The $T / \omega_{\rm K}$-dependence of the resulting resistivity $\rho(T)$, which is found to agree rather well with numerical renormalization group calculations, is shown to be asymptotically exact at high temperatures; to concur well with the Hamann approximation for the s-d model down to $T/\omega_{\rm K} \sim 1$, and to cross over smoothly to the Fermi liquid form $\rho (T) - \rho (0) \propto -(T/\omega_{\rm K})^2$ in the low-temperature limit. The underlying approach, while naturally approximate, is moreover applicable to a broad range of quantum impurity and related models