390 research outputs found

    Conclusion: Message Control at the Margins

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    In the introduction, we identified four key themes that would guide the series of independent yet intersecting analyses that would follow. As those themes were explored and answers were provided to the questions being asked, a series of lessons for operating in the social-media-driven political environment emerged. These lessons shape the larger conclusions that can be derived from the collective efforts of the analyses herein

    Introduction: Controlling the Message in the Social Media Marketplace of Ideas

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    The presidential candidate\u27s campaign faced the threat of being derailed following a scathing depiction of him posted by an individual citizen. Regardless of whether the claims made against the candidate were truthful, the message already had gone viral, and the candidate\u27s campaign flailed in its efforts to respond. Finally, one of the candidate\u27s supporters not affiliated with his campaign repackaged the critic\u27s depiction into a new theme, one that resonated positively with voters. The repackaged message itself continued well beyond its original posting as it was replicated in different forums time and time again

    Bubbling AdS Black Holes

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    We explore the non-BPS analog of `AdS bubbles', which are regular spherically symmetric 1/2 BPS geometries in type IIB supergravity. They have regular horizons and can be thought of as bubbling generalizations of non-extremal AdS black hole solutions in five-dimensional gauged supergravity. Due to the appearance of the Heun equation even at the linearized level, various approximation and numerical methods are needed in order to extract information about this system. We study how the vacuum expectation value and mass of a particular dimension two chiral primary operator depend on the temperature and chemical potential of the thermal Yang-Mills theory. In addition, the mass of the bubbling AdS black holes is computed. As is shown numerically, there are also non-BPS solitonic bubbles which are completely regular and arise from continuous deformations of BPS AdS bubbles.Comment: 37 pages, 2 figure

    Stochastic formulation of the renormalization group: supersymmetric structure and topology of the space of couplings

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    The exact or Wilson renormalization group equations can be formulated as a functional Fokker-Planck equation in the infinite-dimensional configuration space of a field theory, suggesting a stochastic process in the space of couplings. Indeed, the ordinary renormalization group differential equations can be supplemented with noise, making them into stochastic Langevin equations. Furthermore, if the renormalization group is a gradient flow, the space of couplings can be endowed with a supersymmetric structure a la Parisi-Sourlas. The formulation of the renormalization group as supersymmetric quantum mechanics is useful for analysing the topology of the space of couplings by means of Morse theory. We present simple examples with one or two couplings.Comment: 13 pages, based on contribution to "Progress in Supersymmetric Quantum Mechanics" (Valladolid U.), accepted in Journal of Physics

    The Practitioner\u27s Guide to Global Health: an interactive, online, open-access curriculum preparing medical learners for global health experiences

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    BACKGROUND: Short-term experiences in global health (STEGH) are increasingly common in medical education, as they can provide learners with opportunities for service, learning, and sharing perspectives. Academic institutions need high-quality preparatory curricula and mentorship to prepare learners for potential challenges in ethics, cultural sensitivity, and personal safety; however, availability and quality of these are variable. OBJECTIVE: The objective of this study is to create and evaluate an open-access, interactive massive open online course (MOOC) that prepares learners to safely and effectively participate in STEGH, permits flexible and asynchronous learning, is free of charge, and provides a certificate upon successful completion. METHODS: Global health experts from 8 countries, 42 institutions, and 7 specialties collaborated to create The Practitioner\u27s Guide to Global Health (PGGH): the first course of this kind on the edX platform. Demographic data, pre- and posttests, and course evaluations were collected and analyzed. RESULTS: Within its first year, PGGH enrolled 5935 learners from 163 countries. In a limited sample of 109 learners, mean posttest scores were significantly improved (p \u3c 0.01). In the course\u27s second year, 213 sampled learners had significant improvement (p \u3c 0.001). CONCLUSION: We created and evaluated the first interactive, asynchronous, free-of-charge global health preparation MOOC. The course has had significant interest from US-based and international learners, and posttest scores have shown significant improvement

    On-Orbit Measurement of Next Generation Space Solar Cell Technology on the International Space Station

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    Measurement is essential for the evaluation of new photovoltaic (PV) technology for space solar cells. NASA Glenn Research Center (GRC) is in the process of measuring several solar cells in a supplemental experiment on NASA Goddard Space Flight Center's (GSFC) Robotic Refueling Mission's (RRM) Task Board 4 (TB4). Four industry and government partners have provided advanced PV devices for measurement and orbital environment testing. The experiment will be on-orbit for approximately 18 months. It is completely self-contained and will provide its own power and internal data storage. Several new cell technologies including four- junction (4J) Inverted Metamorphic Multijunction (IMM) cells will be evaluated and the results compared to ground-based measurements

    Disorder-Induced Critical Phenomena in Hysteresis: Numerical Scaling in Three and Higher Dimensions

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    We present numerical simulations of avalanches and critical phenomena associated with hysteresis loops, modeled using the zero-temperature random-field Ising model. We study the transition between smooth hysteresis loops and loops with a sharp jump in the magnetization, as the disorder in our model is decreased. In a large region near the critical point, we find scaling and critical phenomena, which are well described by the results of an epsilon expansion about six dimensions. We present the results of simulations in 3, 4, and 5 dimensions, with systems with up to a billion spins (1000^3).Comment: Condensed and updated version of cond-mat/9609072,``Disorder-Induced Critical Phenomena in Hysteresis: A Numerical Scaling Analysis'

    Hysteresis, Avalanches, and Disorder Induced Critical Scaling: A Renormalization Group Approach

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    We study the zero temperature random field Ising model as a model for noise and avalanches in hysteretic systems. Tuning the amount of disorder in the system, we find an ordinary critical point with avalanches on all length scales. Using a mapping to the pure Ising model, we Borel sum the 6−ϵ6-\epsilon expansion to O(ϵ5)O(\epsilon^5) for the correlation length exponent. We sketch a new method for directly calculating avalanche exponents, which we perform to O(ϵ)O(\epsilon). Numerical exponents in 3, 4, and 5 dimensions are in good agreement with the analytical predictions.Comment: 134 pages in REVTEX, plus 21 figures. The first two figures can be obtained from the references quoted in their respective figure captions, the remaining 19 figures are supplied separately in uuencoded forma
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