7,387 research outputs found

    The rise of the Cape gentry

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    Developing Effective K-16 Geoscience Partnerships

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    This article describes the benefits of research partnerships to scientists, students, and teachers. There is growing awareness that the way science is experienced in the K-16 classroom deviates greatly from the experiences of practicing researchers. Whereas researchers are immersed in more open-ended observation and inquiry, many K-16 students find themselves cramming to memorize core scientific content in preparation for standardized examinations. This issue can be mitigated by the development of partnerships in which scientists benefit by added human resources (teachers and students) for data collection and analysis, and teachers and students benefit from a learning process that fosters creativity, sets high standards, teaches problem solving, and is highly motivating. Educational levels: Graduate or professional

    Limit sets for modules over groups on CAT(0) spaces -- from the Euclidean to the hyperbolic

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    The observation that the 0-dimensional Geometric Invariant Σ0(G;A)\Sigma ^{0}(G;A) of Bieri-Neumann-Strebel-Renz can be interpreted as a horospherical limit set opens a direct trail from Poincar\'e's limit set Λ(Γ)\Lambda (\Gamma) of a discrete group Γ\Gamma of M\"obius transformations (which contains the horospherical limit set of Γ\Gamma ) to the roots of tropical geometry (closely related to Σ0(G;A)\Sigma ^{0}(G;A) when G is abelian). We explore this trail by introducing the horospherical limit set, Σ(M;A)\Sigma (M;A), of a G-module A when G acts by isometries on a proper CAT(0) metric space M. This is a subset of the boundary at infinity of M. On the way we meet instances where Σ(M;A)\Sigma (M;A) is the set of all conical limit points, the complement of a spherical building, the complement of the radial projection of a tropical variety, or (via the Bieri-Neumann-Strebel invariant) where it is closely related to the Thurston norm.Comment: This is the final published versio

    The SDSS DR7 Galaxy Angular Power Spectrum

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    We calculate the angular power spectrum of galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) by using a quadratic estimation method with KL-compression. The primary data sample includes over 18 million galaxies covering more than 5,700 square degrees after masking areas with bright objects, reddening greater than 0.2 magnitudes, and seeing of more than 1.5 arcseconds. We test for systematic effects by calculating the angular power spectrum by SDSS stripe and find that these measurements are minimally affected by seeing and reddening. We calculate the angular power spectrum for l \leq 200 multipoles by using 40 bandpowers for the full sample, and l \leq 1000 multipoles using 50 bandpowers for individual stripes. We also calculate the angular power spectrum for this sample separated into 3 magnitude bins with mean redshifts of z = 0.171, z = 0.217, and z = 0.261 to examine the evolution of the angular power spectrum. We determine the theoretical linear angular power spectrum by projecting the 3D power spectrum to two dimensions for a basic comparison to our observational results. By minimizing the {\chi}^2 fit between these data and the theoretical linear angular power spectrum we measure a loosely-constrained fit of {\Omega}_m = 0.31^{+0.18}_{-0.11} with a linear bias of b = 0.94 \pm 0.04
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