3,317 research outputs found

    Bordos and Boundaries: Sustainable Agriculture in the High Altitude Deserts of Northwest Argentina, AD 850-1532

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    Bordos were essential for the long-term sustainability of agriculture in the high altitude desert of Antofagasta de la Sierra in Northwest Argentina during the Late (AD 850 – 1480) and Inca Period (AD 1480 – 1532). Bordos were lineal humps of soil that stimulated the pedogenesis of the predominantly sandy soils of the area. Furthermore, they served as boundaries delimiting irrigation and cultivation fields. Therefore, bordos alongside other technologies were an efficient means by which viable farming was possible in an otherwise marginal agricultural zone. Besides explaining the role of bordos in the context of Northwestern Argentine agriculture this article describes the irrigation systems in place at Antofagasta de la Sierra throughout this period and compares it to the present state of affairs. Our results demonstrate that these late Prehispanic bordos and irrigation networks were well set out and organized such that use of water and soil was efficient, proportional and fair. The Inca do not seem to have disrupted these systems or local autonomy over them. In contrast, modern water and soil is characterized by a household-level decentralized management system. This situation leads to serious conflicts over water use allocations, wastage and flawed irrigation resulting in rising ground salinization.Fil: Salminci, Pedro Miguel. Secretaría de Cultura de la Nación. Dirección Nacional de Cultura y Museos. Instituto Nacional de Antropología y Pensamiento Latinoamericano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tchilinguirian, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Cambridge. Faculty of Archaeology and Anthropology; Reino UnidoFil: Lane, Kevin John. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Cambridge. Faculty of Archaeology and Anthropology; Reino Unid

    Light pollution at high zenith angles, as measured at Cerro Tololo Inter-American Observatory

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    On the basis of measurements of the V-band sky brightness obtained at Cerro Tololo Inter-American Observatory in December 2006 and December 2008 we confirm the functional form of the basic model of Garstang (1989, 1991). At high zenith angles we measure an enhancement of a factor of two over Garstang's later model when there is no marine cloud layer over La Serena/Coquimbo. No corresponding enhancement is found in the B-band.Comment: 12 pages, 4 figures, to be published in the March, 2010, issue of Publs. of the Astron. Soc. of the Pacifi

    Quantum criticality in the two-channel pseudogap Anderson model: A test of the non-crossing approximation

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    We investigate the dynamical properties of the two-channel Anderson model using the noncrossing approximation (NCA) supplemented by numerical renormalization-group calculations. We provide evidence supporting the conventional wisdom that the NCA gives reliable results for the standard two-channel Anderson model of a magnetic impurity in a metal. We extend the analysis to the pseudogap two-channel model describing a semi-metallic host with a density of states that vanishes in power-law fashion at the Fermi energy. This model exhibits continuous quantum phase transitions between weak- and strong-coupling phases. The NCA is shown to reproduce the correct qualitative features of the pseudogap model, including the phase diagram, and to yield critical exponents in excellent agreement with the NRG and exact results. The forms of the dynamical magnetic susceptibility and impurity Green's function at the fixed points are suggestive of frequency-over-temperature scaling.Comment: 6 pages, 10 figures, to appear in the special issue of pss on Quantum Criticality and Novel Phases (QCNP12

    Physics with Beam Tau-Neutrino Appearance at DUNE

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    We explore the capabilities of the upcoming Deep Underground Neutrino Experiment (DUNE) to measure ντ\nu_\tau charged-current interactions and the associated oscillation probability P(νμ→ντ)P(\nu_\mu \to \nu_\tau) at its far detector, concentrating on how such results can be used to probe neutrino properties and interactions. DUNE has the potential to identify significantly more ντ\nu_\tau events than all existing experiments and can use this data sample to nontrivially test the three-massive-neutrinos paradigm by providing complementary measurements to those from the νe\nu_e appearance and νμ\nu_\mu disappearance channels. We further discuss the sensitivity of the ντ\nu_\tau appearance channel to several hypotheses for the physics that may lurk beyond the three-massive-neutrinos paradigm: a non-unitary lepton mixing matrix, the 3+13+1 light neutrinos hypothesis, and the existence of non-standard neutral-current neutrino interactions. Throughout, we also consider the relative benefits of the proposed high-energy tune of the Long-Baseline Neutrino Facility (LBNF) beam-line.Comment: 23 pages, 14 figures, 2 appendice

    Optimal Mass Variables for Semivisible Jets

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    Strongly coupled hidden sector theories predict collider production of invisible, composite dark matter candidates mixed with regular hadrons in the form of semivisible jets. Classical mass reconstruction techniques may not be optimal for these unusual topologies, in which the missing transverse momentum comes from massive particles and has a nontrivial relationship to the visible jet momentum. We apply the artificial event variable network, a semisupervised, interpretable machine learning technique that uses an information bottleneck, to derive superior mass reconstruction functions for several cases of resonant semivisible jet production. We demonstrate that the technique can extrapolate to unknown signal model parameter values. We further demonstrate the viability of conducting an actual search for new physics using this method, by applying the learned functions to standard model background events from quantum chromodynamics.Comment: To be submitted to SciPost Phy

    CaloDiffusion with GLaM for High Fidelity Calorimeter Simulation

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    Simulation is crucial for all aspects of collider data analysis, but the available computing budget in the High Luminosity LHC era will be severely constrained. Generative machine learning models may act as surrogates to replace physics-based full simulation of particle detectors, and diffusion models have recently emerged as the state of the art for other generative tasks. We introduce CaloDiffusion, a denoising diffusion model trained on the public CaloChallenge datasets to generate calorimeter showers. Our algorithm employs 3D cylindrical convolutions, which take advantage of symmetries of the underlying data representation. To handle irregular detector geometries, we augment the diffusion model with a new geometry latent mapping (GLaM) layer to learn forward and reverse transformations to a regular geometry that is suitable for cylindrical convolutions. The showers generated by our approach are nearly indistinguishable from the full simulation, as measured by several different metrics.Comment: 21 pages, 9 figure
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