229 research outputs found

    Independent Loop Invariants for 2+1 Gravity

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    We identify an explicit set of complete and independent Wilson loop invariants for 2+1 gravity on a three-manifold M=R×ΣgM=\R\times\Sigma^g, with Σg\Sigma^g a compact oriented Riemann surface of arbitrary genus gg. In the derivation we make use of a global cross section of the PSU(1,1)PSU(1,1)-principal bundle over Teichm\"uller space given in terms of Fenchel-Nielsen coordinates.Comment: 11pp, 2 figures (postscript, compressed and uu-encoded), TeX, Pennsylvania State University, CGPG-94/7-

    On fusion algebra of chiral SU(N)kSU(N)_{k} models

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    We discuss some algebraic setting of chiral SU(N)kSU(N)_{k} models in terms of the statistical dimensions of their fields. In particular, the conformal dimensions and the central charge of the chiral SU(N)kSU(N)_{k} models are calculated from their braid matrices. Futhermore, at level K=2, we present the characteristic polynomials of their fusion matrices in a factored form.Comment: 11 pages, ioplpp

    New Loop Representations for 2+1 Gravity

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    Since the gauge group underlying 2+1-dimensional general relativity is non-compact, certain difficulties arise in the passage from the connection to the loop representations. It is shown that these problems can be handled by appropriately choosing the measure that features in the definition of the loop transform. Thus, ``old-fashioned'' loop representations - based on ordinary loops - do exist. In the case when the spatial topology is that of a two-torus, these can be constructed explicitly; {\it all} quantum states can be represented as functions of (homotopy classes of) loops and the scalar product and the action of the basic observables can be given directly in terms of loops.Comment: 28pp, 1 figure (postscript, compressed and uuencoded), TeX, Pennsylvania State University, CGPG-94/5-

    Dynamical Stability of Six-Dimensional Warped Brane-Worlds

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    We study a generalization of the Randall-Sundrum mechanism for generating the weak/Planck hierarchy, which uses two rather than one warped extra dimension, and which requires no negative tension branes. A 4-brane with one exponentially large compact dimension plays the role of the Planck brane. We investigate the dynamical stability with respect to graviton, graviphoton and radion modes. The radion is shown to have a tachyonic instability for certain models of the 4-brane stress-energy, while it is stable in others, and massless in a special case. If stable, its mass is in the milli-eV range, for parameters of the model which solve the hierarchy problem. The radion is shown to couple to matter with gravitational strength, so that it is potentially detectable by submillimeter-range gravity experiments. The radion mass can be increased using a bulk scalar field in the manner of Goldberger and Wise, but only to order MeV, due to the effect of the large extra dimension. The model predicts a natural scale of 10^{13} GeV on the 4-brane, making it a natural setting for inflation from the ultraviolet brane.Comment: 28 pages, 7 figure

    Sigma-model for Generalized Composite p-branes

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    A multidimensional gravitational model containing several dilatonic scalar fields and antisymmetric forms is considered. The manifold is chosen in the form M = M_0 x M_1 x ... x M_n, where M_i are Einstein spaces (i > 0). The block-diagonal metric is chosen and all fields and scale factors of the metric are functions on M_0. For the forms composite (electro-magnetic) p-brane ansatz is adopted. The model is reduced to gravitating self-interacting sigma-model with certain constraints. In pure electric and magnetic cases the number of these constraints is m(m - 1)/2 where m is number of 1-dimensional manifolds among M_i. In the "electro-magnetic" case for dim M_0 = 1, 3 additional m constraints appear. A family of "Majumdar-Papapetrou type" solutions governed by a set of harmonic functions is obtained, when all factor-spaces M_k are Ricci-flat. These solutions are generalized to the case of non-Ricci-flat M_0 when also some additional "internal" Einstein spaces of non-zero curvature are added to M. As an example exact solutions for D = 11 supergravity and related 12-dimensional theory are presented.Comment: 33 pages, Latex. Some corrections and rearrangements are mad

    フィールドにおける3次元歩行動作解析システムの開発

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    The purpose of this study was to clarify the effectiveness and possible problems that may occur when using the walking movement analysis system of three dimensions in the field. Cinematography was performed using an optical signal with four sets of digital camcorders synchronously. First, in order to clarify measurement accuracy, the error of distance and angle in the actual value and calculation value, was examined. Next, the walking movements during free walking in the field using this system was analyzed employing ten young men,and the variables were compared with studies preceding this study. The following results were obtained: 1.It is more desirable to digitize using large projectors, such as a huge screen, when analyzing fine angles or distance of images of the whole body that is photographed. 2.It was thought that if the definition of each joint angle or the height of toe at heel contact is the same, the value of each variable acquired is similar to preceding studies. Therefore,it can be concluded that this walking movement analysis system of three dimensions is effective. When analyzing images, it is necessary to raise measurement accuracy and to consider error factors irrespective of the field or laboratory
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