8,544 research outputs found

    Supermembrane with Non-Abelilan Gauging and Chern-Simons Quantization

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    We present non-Abelian gaugings of supermembrane for general isometries for compactifications from eleven-dimensions, starting with Abelian case as a guide. We introduce a super Killing vector in eleven-dimensional superspace for a non-Abelian group G associated with the compact space B for a general compactification, and couple it to a non-Abelian gauge field on the world-volume. As a technical tool, we use teleparallel superspace with no manifest local Lorentz covariance. Interestingly, the coupling constant is quantized for the non-Abelian group G, due to its generally non-trivial mapping \pi_3(G).Comment: 16 pages, no figures. The content has been considerably changed with non-Abelian generalizatio

    The ambivalent shadow of the pre-Wilsonian rise of international law

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    The generation of American international lawyers who founded the American Society of International Law in 1906 and nurtured the soil for what has been retrospectively called a “moralistic legalistic approach to international relations” remains little studied. A survey of the rise of international legal literature in the U.S. from the mid-19th century to the eve of the Great War serves as a backdrop to the examination of the boosting effect on international law of the Spanish American War in 1898. An examination of the Insular Cases before the US Supreme Court is then accompanied by the analysis of a number of influential factors behind the pre-war rise of international law in the U.S. The work concludes with an examination of the rise of natural law doctrines in international law during the interwar period and the critiques addressed.by the realist founders of the field of “international relations” to the “moralistic legalistic approach to international relation

    Hypervelocity particle capture: Some considerations regarding suitable target media

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    Hypervelocity particles colliding with passive capture media will be traversed by shock waves; depending on the stress amplitude, the particle may remain solid or it may melt or vaporize. Any capture mechanism considered for cosmic dust collection in low Earth-orbit must be designed such that sample alteration and hence loss of scientific information is minimized. Capture of pristine particles is fundamentally difficult, because the specific heat of melting and even vaporization is exceeded upon impact at typical, geocentric encounter velocities. From the results of calculated and observed melting behaviors it is concluded that shock stresses in excess of 50 GPA should be avoided during hypervelocity particle capture on board Space Station and that stresses 20 GPa, even at 15 km/s collision velocities, should constitute desirable instrument design goals. Some principal characteristics of the capture medium that may satisfy these requirements are identified

    Impact cratering in reduced-gravity environments: Early experiments on the NASA KC-135 aircraft

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    Impact experimentation on the NASA KC-135 Reduced-Gravity Aircraft was shown to be possible, practical, and of considerable potential use in examining the role of gravity on various impact phenomena. With a minimal facility, crater dimensional and growth-times were measured, and have demonstrated both agreement and disagreement with predictions. A larger facility with vacuum capability and a high-velocity gun would permit a much wider range of experimentation

    Projectile compositions and modal frequencies on the chemistry of micrometeoroids LDEF experiment

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    The Chemistry of Micrometeoroids Experiment (LDEF instrument A0187-1) exposed witness plates of high-purity gold (greater than 99.99 percent Au) and commercial aluminum (greater than 99 percent Al) with the objective of analyzing the residues of cosmic-dust and orbital-debris particles associated with hypervelocity impact craters. The gold substrates were located approximately 8 deg off LDEF's trailing edge (Bay A03), while the aluminum surfaces resided in Bay A11, approximately 52 deg from LDEF's leading edge. SEM-EDX techniques were employed to analyze the residues associated with 199 impacts on the gold and 415 impacts on the aluminum surfaces. The residues that could be analyzed represent natural or man-made materials. The natural particles dominate at all particle sizes less than 5 micron. It is possible to subdivide both particle populations into subclasses. Chondritic compositions dominate the natural impactors (71 percent), followed by monomineralic, mafic-silicate compositions (26 percent), and by Fe-Ni rich sulfides (approximately 3 percent). Approximately 30 percent of all craters on the gold collectors were caused by man-made debris such as aluminum, paint flakes, and other disintegrated, structural and electronic components. Equations-of-state and associated calculations of shock stresses for typical LDEF impacts into the gold and aluminum substrates suggest that substantial vaporization may have occurred during many of the impacts and is the reason why approximately 50 percent of all craters did not contain sufficient residue to permit analysis by the SEM-EDX technique. After converting the crater diameters into projectile sizes using encounter speeds typical for the trailing-edge and forward-facing (Row 11) directions, and accounting for normalized exposure conditions of the CME collectors, we derived the absolute and relative fluxes of specific projectile classes. The natural impactors encounter all LDEF pointing directions with comparable, modal frequencies suggesting compositional (and dynamic) homogeneity of the interplanetary-dust environment in near-Earth orbit

    Three-D crater analysis of LDEF impact features from stereo imagery

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    The preliminary results from attempts to derive depth and diameter information from digitized stereo images of impact features on the LDEF are reported. Contrary to our prior assumption, we find that impact craters in the T6 A1 alloy are not paraboloid in cross section, but rather are better described by a 6th-order polynomial curve. We explore the implications of this discovery

    A new orthogonalization procedure with an extremal property

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    Various methods of constructing an orthonomal set out of a given set of linearly independent vectors are discussed. Particular attention is paid to the Gram-Schmidt and the Schweinler-Wigner orthogonalization procedures. A new orthogonalization procedure which, like the Schweinler- Wigner procedure, is democratic and is endowed with an extremal property is suggested.Comment: 7 pages, latex, no figures, To appear in J. Phys

    One-loop Beta Functions for the Orientable Non-commutative Gross-Neveu Model

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    We compute at the one-loop order the beta-functions for a renormalisable non-commutative analog of the Gross Neveu model defined on the Moyal plane. The calculation is performed within the so called x-space formalism. We find that this non-commutative field theory exhibits asymptotic freedom for any number of colors. The beta-function for the non-commutative counterpart of the Thirring model is found to be non vanishing.Comment: 16 pages, 9 figure

    ASEAN-EU university network programme on EMC and SI education

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    This paper reports about a project for the creation of an innovative university course devoted to the preparation of future electronic designers to the challenges imposed by the assurance of the electrical performance of high-speed electronic systems. The target groups are future university teaching staff and future electronic systems designers. Activities are developed by means of sharing research results, seminars, experience exchange and the development of demonstrators to be used for teaching. The partnership is composed by Technical University of Turin (Italy), University of Hannover (Germany), University of Nottingham (UK), Nanyang Technological University (Singapore) and King Monguts Institute of Technology Lad-krabang, Bangkok (Thailand). The program is partially funded by the European Commission under the ASEAN-EU University Network Programme (AUNP) and its duration is 24 months
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