20,808 research outputs found

    Diffuse galactic light observations at 206 selected areas

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    Space-based, observational diffuse galactic light (DGL) levels at 4400 A are presented as a function of galactic latitude (b). A peak in the ratio of DGL to direct starlight is apparent at the absolute value of b = 5 to 15 deg, where one third of the celestial brightness is due to scattered light. Another salient feature is the general decrease in the relative contribution of the DGL at intermediate and high galactic latitudes. The relationship DGL (S sub 10(V)sub G2V, 4400 A) = 2.4 x 10 (exp -20 N(sub H I) atoms/sq cm may be used to estimate the brightness of DGL from neutral hydrogen column densities when N(sub H I) is less than 2 x 10(exp 21) atoms/sq cm. The results presented here have been used to characterize the interstellar dust in the general interstellar medium. A galaxy model that reproduces observed brightness levels was used to compare theoretical and observed DGL values. This determines two grain parameters - the albedo and the asymmetry of the scattering phase function (g). The results are albedo = .61 + or - .07, and g = .6 + or - .2

    The Dynamics of Intra-jurisdictional Relations in the Inuit Regions of the Canadian Arctic: An Institutionalist Perspective

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    One of the most exciting developments in Canadian federalism has been the emergence of Aboriginal self-governing regions. This paper constructs a theoretical framework for exploring the evolution of intra-jurisdictional relations in the self-governing Inuit regions of the Canadian Arctic. Intra-jurisdictional relations in these regions are characterized by a unique set of relationships between elected governments and organizations that represent the beneficiaries of land-claims agreements. Using the literature on historical institutionalism, we argue that the nature of Inuit intra-jurisdictional relations following the establishment of self-government can be explained by the institutional choices made prior to the signing of land-claims agreements and/or self-government agreements. To illustrate the potential of our framework for analysing Inuit intra-jurisdictional relations, we briefly examine the experiences of Nunavut, an Inuit-dominated region and the newest territory in the Canadian federation

    Black Holes, Shock Waves, and Causality in the AdS/CFT Correspondence

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    We find the expectation value of the energy-momentum tensor in the CFT corresponding to a moving black hole in AdS. Boosting the black hole to the speed of light, keeping the total energy fixed, yields a gravitational shock wave in AdS. The analogous procedure on the field theory side leads to ``light cone'' states, i.e., states with energy-momentum tensor localized on the light cone. The correspondence between the gravitational shock wave and these light cone states provides a useful tool for testing causality. We show, in several examples, how the CFT reproduces the causal relations in AdS.Comment: Minor corrections, references adde

    Nonlinear Inflaton Fragmentation after Preheating

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    We consider the nonlinear dynamics of inflaton fragmentation during and after preheating in the simplest model of chaotic inflation. While the earlier regime of parametric resonant particle production and the later turbulent regime of interacting fields evolving towards equilibrium are well identified and understood, the short intermediate stage of violent nonlinear dynamics remains less explored. Lattice simulations of fully nonlinear preheating dynamics show specific features of this intermediate stage: occupation numbers of the scalar particles are peaked, scalar fields become significantly non-gaussian and the field dynamics become chaotic and irreversible. Visualization of the field dynamics in configuration space reveals that nonlinear interactions generate non-gaussian inflaton inhomogeneities with very fast growing amplitudes. The peaks of the inflaton inhomogeneities coincide with the peaks of the scalar field(s) produced by parametric resonance. When the inflaton peaks reach their maxima, they stop growing and begin to expand. The subsequent dynamics is determined by expansion and superposition of the scalar waves originating from the peaks. Multiple wave superposition results in phase mixing and turbulent wave dynamics. Thus, the short intermediate stage is defined by the formation, expansion and collision of bubble-like field inhomogeneities associated with the peaks of the original gaussian field. This process is qualitatively similar to the bubble-like inflaton fragmentation that occurs during tachyonic preheating after hybrid or new inflation.Comment: 9 pages, 6 fig

    Entrepreneurship for Veterans with Disabilities: Lessons Learned from the Field

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    A 2009 research brief produced for the NTAR Leadership Center, a consortium led by the John H. Heldrich Center for Workforce Development at Rutgers, The State University of New Jersey. Founded in 2007 under a grant/contract with the Office of Disability Employment Policy at the U.S. Department of Labor, the NTAR Leadership Center's mission is to build capacity and leadership at the federal, state, and local levels to enable change across workforce development and disability-specific systems that will increase employment and economic self-sufficiency for adults with disabilities. This brief examines entrepreneurship as a viable option for veterans with disabilities, particularly those returning from the present-day conflicts in the Middle East. As entrepreneurs, veterans have an array of opportunities to customize their employment, accommodate their challenges, maximize their strengths and skills, and achieve their financial and career goals. This brief takes a close look at one program -- the Entrepreneurship Boot Camp -- and discusses some lessons learned from the operation of this program

    Inflaton Fragmentation After lambda phi^4 Inflation

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    We use lattice simulations to examine the detailed dynamics of inflaton fragmentation during and after preheating in λϕ4\lambda \phi^4 chaotic inflation. The dynamics are qualitatively similar to preheating after m2ϕ2m^2 \phi^2 inflation, involving the exponential growth and subsequent expansion and collision of bubble-like inhomogeneities of the inflaton and other scalar fields. During this stage fluctuations of the fields become strongly non-Gaussian. In the quartic theory, the conformal nature of the theory allows us to extend our simulations to much greater times than is possible for the quadratic model. With these longer simulations we have been able to determine the time scale on which Gaussianity is restored, which occurs after a time on the order of a thousand inflaton oscillations.Comment: 5 pages, 5 figure

    Environmental assessment for the Satellite Power System (SPS): Studies of honey bees exposed to 2.45 GHz continuous wave electromagnetic energy

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    Post treatment brood development was normal and teratological effects were not detected at exposures of 3 to 50 mw sq cm for 30 minutes. Post treatment survival, longevity, orientation, navigation, and memory of adult bees were also normal after exposures of 3 to 50 mw sq cm for 30 minutes. Post treatment longevity of confined bees in the laboratory was normal after exposures of 3 to 50 mw sq cm for 24 hours. Thermoregulation of brood nest, foraging activity, brood rearing, and social interaction were not affected by chronic exposure to 1 mw sq cm during 28 days. In dynamic behavioral bioassays the frequency of entry and duration of activity of unrestrained, foraging adult bees was identical in microwave exposed areas versus control areas

    Theoretical Foundations and Empirical Evaluations of Partisan Fairness in District-Based Democracies

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    We clarify the theoretical foundations of partisan fairness standards for district-based democratic electoral systems, including essential assumptions and definitions not previously recognized, formalized, or in some cases even discussed. We also offer extensive empirical evidence for assumptions with observable implications. We cover partisan symmetry, the most commonly accepted fairness standard, and other perspectives. Throughout, we follow a fundamental principle of statistical inference too often ignored in this literature—defining the quantity of interest separately so its measures can be proven wrong, evaluated, and improved. This enables us to prove which of the many newly proposed fairness measures are statistically appropriate and which are biased, limited, or not measures of the theoretical quantity they seek to estimate at all. Because real-world redistricting and gerrymandering involve complicated politics with numerous participants and conflicting goals, measures biased for partisan fairness sometimes still provide useful descriptions of other aspects of electoral systems
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