79,451 research outputs found

    L2L_2 boosting in kernel regression

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    In this paper, we investigate the theoretical and empirical properties of L2L_2 boosting with kernel regression estimates as weak learners. We show that each step of L2L_2 boosting reduces the bias of the estimate by two orders of magnitude, while it does not deteriorate the order of the variance. We illustrate the theoretical findings by some simulated examples. Also, we demonstrate that L2L_2 boosting is superior to the use of higher-order kernels, which is a well-known method of reducing the bias of the kernel estimate.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ160 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

    Non-renormalization of two and three Point Correlators of N=4 SYM in N=1 Superspace

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    Certain two and three point functions of gauge invariant primary operators of N=4{\cal N}=4 SYM are computed in N=1{\cal N}=1 superspace keeping all the th\th-components. This allows one to read off many component descendent correlators. Our results show the only possible gYM2g^2_{YM} corrections to the free field correlators are contact terms. Therefore they vanish for operators at separate points, verifying the known non-renormalization theorems. This also implies the results are consistent with N=4{\cal N}=4 supersymmetry even though the Lagrangian we use has only N=1{\cal N}=1 manifest supersymmetry. We repeat some of the calculations using supersymmetric Landau gauge and obtain, as expected, the same results as those of supersymmetric Feynman gauge.Comment: 10 pages, 20 eps figures, references adde

    Cold Compressed Baryonic Matter with Hidden Local Symmetry and Holography

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    I describe a novel phase structure of cold dense baryonic matter predicted in a hidden local symmetry approach anchored on gauge theory and in a holographic dual approach based on the Sakai-Sugimoto model of string theory. This new phase is populated with baryons with half-instanton quantum number in the gravity sector which is dual to half-skyrmion in gauge sector in which chiral symmetry is restored while light-quark hadrons are in the color-confined phase. It is suggested that such a phase that aries at a density above that of normal nuclear matter and below or at the chiral restoration point can have a drastic influence on the properties of hadrons at high density, in particular on short-distance interactions between nucleons, e.g., multi-body forces at short distance and hadrons -- in particular kaons -- propagating in a dense medium. Potentially important consequences on the structure of compact stars will be predicted.Comment: 15 pages, to appear in proceedings of "Strong Coupling Gauge Theories in LHC Era (SCGT09)," Nagoya, Japa

    Anisotropic strains and magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3}

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    Thin films of perovskite manganite La_{0.7}Ca_{0.3}MnO_{3} were grown epitaxially on SrTiO_3(100), MgO(100) and LaAlO_3(100) substrates by the pulsed laser deposition method. Microscopic structures of these thin film samples as well as a bulk sample were fully determined by x-ray diffraction measurements. The unit cells of the three films have different shapes, i.e., contracted tetragonal, cubic, and elongated tetragonal for SrTiO_3, MgO, and LaAlO_3 cases, respectively, while the unit cell of the bulk is cubic. It is found that the samples with cubic unit cell show smaller peak magnetoresistance than the noncubic ones do. The present result demonstrates that the magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3} can be controlled by lattice distortion via externally imposed strains.Comment: Revtex, 10 pages, 2 figure
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