8,319 research outputs found

    Geodesics on the Ellipsoid and Monodromy

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    The equations for geodesic flow on the ellipsoid are well known, and were first solved by Jacobi in 1838 by separating the variables of the Hamilton-Jacobi equation. In 1979 Moser investigated the case of the general ellipsoid with distinct semi-axes and described a set of integrals which weren't know classically. After reviewing the properties of geodesic flow on the three dimensional ellipsoid with distinct semi-axes, we investigate the three dimensional ellipsoid with the two middle semi-axes being equal, corresponding to a Hamiltonian invariant under rotations. The system is Liouville-integrable and thus the invariant manifolds corresponding to regular points of the energy momentum map are 3-dimensional tori. An analysis of the critical points of the energy momentum maps gives the bifurcation diagram. We find the fibres of the critical values of the energy momentum map, and carry out an analysis of the action variables. We show that the obstruction to the existence of single valued globally smooth action variables is monodromy.Comment: 24 pages, 7 figure

    Phase equilibrium modeling for high temperature metallization on GaAs solar cells

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    Recent trends in performance specifications and functional requirements have brought about the need for high temperature metallization technology to be developed for survivable DOD space systems and to enhance solar cell reliability. The temperature constitution phase diagrams of selected binary and ternary systems were reviewed to determine the temperature and type of phase transformation present in the alloy systems. Of paramount interest are the liquid-solid and solid-solid transformations. Data are being utilized to aid in the selection of electrical contact materials to gallium arsenide solar cells. Published data on the phase diagrams for binary systems is readily available. However, information for ternary systems is limited. A computer model is being developed which will enable the phase equilibrium predictions for ternary systems where experimental data is lacking

    Double non-equivalent chain structure on vicinal Si(557)-Au surface

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    We study electronic and topographic properties of the vicinal Si(557)-Au surface using scanning tunneling microscopy and reflection of high energy electron diffraction technique. STM data reveal double wire structures along terraces. Moreover behavior of the voltage dependent STM tip - surface distance is different in different chains. While the one chain shows oscillations of the distance which are sensitive to the sign of the voltage bias, the oscillations in the other chain remain unchanged with respect to the positive/negative biases. This suggests that one wire has metallic character while the other one - semiconducting. The experimental results are supplemented by theoretical calculations within tight binding model suggesting that the observed chains are made of different materials, one is gold and the other one is silicon chain.Comment: 9 pages, 12 figures, accepted for publication in Phys. Rev.

    Jet substructure as a new Higgs search channel at the LHC

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    It is widely considered that, for Higgs boson searches at the Large Hadron Collider, WH and ZH production where the Higgs boson decays to b anti-b are poor search channels due to large backgrounds. We show that at high transverse momenta, employing state-of-the-art jet reconstruction and decomposition techniques, these processes can be recovered as promising search channels for the standard model Higgs boson around 120 GeV in mass.Comment: 4 pages, 3 figure
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