24,708 research outputs found

    Point-source detection system rejects spatially extended radiation sources

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    System employing digital space correlation to suppress false target signals in a point-target tracking device is a reliable method for discriminating a distant target from false targets in the field of view of an infrared detection system or tracking device

    Comment on "Perfect imaging with positive refraction in three dimensions"

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    Leonhard and Philbin [Phys. Rev. A 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit

    Polymers for spacecraft hardware - Materials characterization, part I Interim report, Mar. - Dec. 1966

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    Environmental testing of polymeric materials for spacecraft hardwar

    Global Classical Solutions of the Boltzmann Equation with Long-Range Interactions and Soft Potentials

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    In this work we prove global stability for the Boltzmann equation (1872) with the physical collision kernels derived by Maxwell in 1866 for the full range of inverse power intermolecular potentials, r(p1)r^{-(p-1)} with p>2p>2. This completes the work which we began in (arXiv:0912.0888v1). We more generally cover collision kernels with parameters s(0,1)s\in (0,1) and γ\gamma satisfying γ>(n2)2s\gamma > -(n-2)-2s in arbitrary dimensions Tn×Rn\mathbb{T}^n \times \mathbb{R}^n with n2n\ge 2. Moreover, we prove rapid convergence as predicted by the Boltzmann H-Theorem. When γ+2s0\gamma + 2s \ge 0, we have exponential time decay to the Maxwellian equilibrium states. When γ+2s<0\gamma + 2s < 0, our solutions decay polynomially fast in time with any rate. These results are constructive. Additionally, we prove sharp constructive upper and lower bounds for the linearized collision operator in terms of a geometric fractional Sobolev norm; we thus observe that a spectral gap exists only when γ+2s0\gamma + 2s \ge 0, as conjectured in Mouhot-Strain (2007).Comment: This file has not changed, but this work has been combined with (arXiv:0912.0888v1), simplified and extended into a new preprint, please see the updated version: arXiv:1011.5441v

    Numerical study of the relativistic three-body quantization condition in the isotropic approximation

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    We present numerical results showing how our recently proposed relativistic three-particle quantization condition can be used in practice. Using the isotropic (generalized ss-wave) approximation, and keeping only the leading terms in the effective range expansion, we show how the quantization condition can be solved numerically in a straightforward manner. In addition, we show how the integral equations that relate the intermediate three-particle infinite-volume scattering quantity, Kdf,3\mathcal K_{\text{df},3}, to the physical scattering amplitude can be solved at and below threshold. We test our methods by reproducing known analytic results for the 1/L1/L expansion of the threshold state, the volume dependence of three-particle bound-state energies, and the Bethe-Salpeter wavefunctions for these bound states. We also find that certain values of Kdf,3\mathcal K_{\text{df},3} lead to unphysical finite-volume energies, and give a preliminary analysis of these artifacts.Comment: 32 pages, 21 figures, JLAB-THY-18-2657, CERN-TH-2018-046; version 2: corrected typos, updated references, minor stylistic changes---consistent with published versio
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