2,033 research outputs found

    Beyond the Small-Angle Approximation For MBR Anisotropy from Seeds

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    In this paper we give a general expression for the energy shift of massless particles travelling through the gravitational field of an arbitrary matter distribution as calculated in the weak field limit in an asymptotically flat space-time. It is {\it not} assumed that matter is non-relativistic. We demonstrate the surprising result that if the matter is illuminated by a uniform brightness background that the brightness pattern observed at a given point in space-time (modulo a term dependent on the oberver's velocity) depends only on the matter distribution on the observer's past light-cone. These results apply directly to the cosmological MBR anisotropy pattern generated in the immediate vicinity of of an object like a cosmic string or global texture. We apply these results to cosmic strings, finding a correction to previously published results for in the small-angle approximation. We also derive the full-sky anisotropy pattern of a collapsing texture knot.Comment: 23 pages, FERMILAB-Pub-94/047-

    A Finite-Bound Partition Equinumerosity Result Generalizing a Solution of a Problem Posed by Andrews and Deutsch

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    We introduce a finite-bound extension of a partition equinumerosity result which was orignally proposed as a problem by Andrews and Deutsch in 2016, and given a generalized form in 2018 by Smoot and Yang. We also give a simple bijective proof, itself an extension of the proof given of the 2018 generalization

    The Dipole Observed in the COBE DMR Four-Year Data

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    The largest anisotropy in the cosmic microwave background (CMB) is the ≈3\approx 3 mK dipole assumed to be due to our velocity with respect to the CMB. Using the four year data set from all six channels of the COBE Differential Microwave Radiometers (DMR), we obtain a best-fit dipole amplitude 3.358±0.001±0.0233.358 \pm 0.001 \pm 0.023 mK in the direction (l,b)=(264deg⁥.31±0deg⁥.04±0deg⁥.16,+48deg⁥.05±0deg⁥.02±0deg⁥.09)(l,b)=(264\deg.31 \pm 0\deg.04 \pm 0\deg.16, +48\deg.05 \pm 0\deg.02 \pm 0\deg.09), where the first uncertainties are statistical and the second include calibration and combined systematic uncertainties. This measurement is consistent with previous DMR and FIRAS resultsComment: New and improved version; to be published in ApJ next mont

    A scale-dependent cosmology for the inhomogeneous Universe

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    A scale-dependent cosmology is proposed in which the Robertson-Walker metric and the Einstein equation are modified in such a way that Ω0\Omega_0, H0H_0 and the age of the Universe all become scale-dependent. Its implications on the observational cosmology are discussed.Comment: 7 pages, in RevTex. To be appeared in TAUP '9

    Contribution of Extragalactic Infrared Sources to CMB Foreground Anisotropy

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    We estimate the level of confusion to Cosmic Microwave Background anisotropy measurements caused by extragalactic infrared sources. CMB anisotropy observations at high resolution and high frequencies are especially sensitive to this foreground. We use data from the COBE satellite to generate a Galactic emission spectrum covering mm and sub-mm wavelengths. Using this spectrum as a template, we predict the microwave emission of the 5319 brightest infrared galaxies seen by IRAS. We simulate skymaps over the relevant range of frequencies (30-900 GHz) and instrument resolutions (10'-10 degrees Full Width Half Max). Analysis of the temperature anisotropy of these skymaps shows that a reasonable observational window is available for CMB anisotropy measurements.Comment: 14 pages (LaTex source), 3 PostScript figures. Final version, to appear in ApJLetters May 1. Expanded discussion of systematic error

    Archeops, mapping the CMB sky from large to small angular scales

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    Archeops is a balloon-borne experiment designed to measure the temperature fluctuations of the CMB on a large region of the sky (≃30\simeq 30%) with a high angular resolution (10 arcminutes) and a high sensitivity (60ÎŒK60\mu K per pixel). Archeops will perform a measurement of the CMB anisotropies power spectrum from large angular scales (ℓ≃30\ell\simeq 30) to small angular scales (ℓ≃800\ell \simeq 800). Archeops flew for the first time for a test flight in July 1999 from Sicily to Spain and the first scientific flight took place from Sweden to Russia in January 2001. The data analysis is on its way and I present here preliminary results, realistic simulations showing the expected accuracy on the measurement of the power spectrum and perspectives for the incoming flights (Winter 2001/2003).Comment: 6 pages, 6 figures, proceedings to TAUP2001 conference, LNGS, Italy, Sept. 200

    Use of Current 2010 Forest Disturbance Monitoring Products for the Conterminous United States in Aiding a National Forest Threat Early Warning System

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    This presentation discusses contributions of near real time (NRT) MODIS forest disturbance detection products for the conterminous United States to an emerging national forest threat early warning system (EWS). The latter is being developed by the USDA Forest Service s Eastern and Western Environmental Threat Centers with help from NASA Stennis Space Center and the Oak Ridge National Laboratory. Building off work done in 2009, this national and regional forest disturbance detection and viewing capability of the EWS employs NRT MODIS NDVI data from the USGS eMODIS group and historical NDVI data from standard MOD13 products. Disturbance detection products are being computed for 24 day composites that are refreshed every 8 days. Products for 2010 include 42 dates of the 24 day composites. For each compositing date, we computed % change in forest maximum NDVI products for 2010 with respect to each of three historical baselines of 2009, 2007-2009, and 2003-2009,. The three baselines enable one to view potential current, recent, and longer term forest disturbances. A rainbow color table was applied to each forest change product so that potential disturbances (NDVI drops) were identified in hot color tones and growth (NDVI gains) in cold color tones. Example products were provided to end-users responsible for forest health monitoring at the Federal and State levels. Large patches of potential forest disturbances were validated based on comparisons with available reference data, including Landsat and field survey data. Products were posted on two internet mapping systems for US Forest Service internal and collaborator use. MODIS forest disturbance detection products were computed and posted for use in as little as 1 day after the last input date of the compositing period. Such products were useful for aiding aerial disturbance detection surveys and for assessing disturbance persistence on both inter- and intra-annual scales. Multiple 2010 forest disturbance events were detected across the nation, including damage from ice storms, tornadoes, caterpillars, bark beetles, and wildfires. This effort enabled improved NRT forest disturbance monitoring capabilities for this nation-wide forest threat EWS
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