51,453 research outputs found

    Lifting of Quantum Linear Spaces and Pointed Hopf Algebras of order p^3

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    We propose the following principle to study pointed Hopf algebras, or more generally, Hopf algebras whose coradical is a Hopf subalgebra. Given such a Hopf algebra A, consider its coradical filtration and the associated graded coalgebra grad(A). Then grad(A) is a graded Hopf algebra, since the coradical A_0 of A is a Hopf subalgebra. In addition, there is a projection \pi: grad(A) \to A_0; let R be the algebra of coinvariants of \pi. Then, by a result of Radford and Majid, R is a braided Hopf algebra and grad(A) is the bosonization (or biproduct) of R and A_0: grad(A) is isomorphic to (R # A_0). The principle we propose to study A is first to study R, then to transfer the information to grad(A) via bosonization, and finally to lift to A. In this article, we apply this principle to the situation when R is the simplest braided Hopf algebra: a quantum linear space. As consequences of our technique, we obtain the classification of pointed Hopf algebras of order p^3 (p an odd prime) over an algebraically closed field of characteristic zero; with the same hypothesis, the characterization of the pointed Hopf algebras whose coradical is abelian and has index p or p^2; and an infinite family of pointed, non-isomorphic, Hopf algebras of the same dimension. This last result gives a negative answer to a conjecture of I. Kaplansky.Comment: AmsTeX, 28 pages. To be published in J. of Algebr

    IR-TF Relation In The Zone Of Avoidance With 2MASS

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    Using the Tully-Fisher relation, one can map the peculiar velocity field and estimate the mass in regions such as the Great Attractor. 2MASS is surveying the full sky in J, H and K bands and has the great advantage that it allows us to detect galaxies more uniformly to lower Galactic latitude than optical surveys. This study shows the feasibility of using 2MASS and the TF relation to probe large scale structure. We found that (i) we can use axis ratio b/ab/a up to 0.5; (ii) intrinsic extinction is present (up to 0.5mag at J, 0.1 mag at K); (iii) the zero-point of the TF relation is independent of the 2MASS magnitude measurement and is consistent with the HST Key-Project value; (iv) the 2MASS K-band 20th mag/arcsec2^2 isophotal aperture magnitude produces the best TF relation; and (v) there is no type dependence of the residualsComment: 8 pages, Latex using newpasp.sty. Matches version to appear in Mapping the Hidden Universe: The Universe Behind the Milky Way - The Universe in HI, ASP Conference Series 2000, eds R.C.Kraan-Korteweg, P.A. Henning and H. Andernach (matched to published version; abstract bug in v2 fixed

    Magnetic field induced 3D to 1D crossover in Sr0:9La0:1CuO2

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    The effect of the magnetic field on the critical behavior of Sr0:9La0:1CuO2 is explored in terms of reversible magnetization data. As the correlation length transverse to the magnetic field Hi,applied along the i-axis, cannot grow beyond the limiting magnetic length LHi, related to the average distance between vortex lines, one expects a magnetic field induced finite size effect. Invoking the scaling theory of critical phenomena we provide clear evidence for this effect. It implies that in type II superconductors there is a 3D to 1D crossover line Hpi(T). Consequently, below Tc and above Hpi(T) uperconductivity is confined to cylinders with diameter LHi(1D). Accordingly, there is no continuous phase transition in the (H,T)-plane along the Hc2-lines as predicted by the mean-field treatment.Comment: 4 pages, 5 figure

    Pressure effects on the superconducting properties of YBa_2Cu_4O_8

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    Measurements of the magnetization under high hydrostatic pressure (up to 10.2 kbar) in YBa_2Cu_4O_8 were carried out. From the scaling analysis of the magnetization data the pressure induced shifts of the transition temperature T_c, the volume V and the anisotropy \gamma have been obtained. It was shown that the pressure induced relative shift of T_c mirrors essentially that of the anisotropy. This observation uncovers a novel generic property of anisotropic type II superconductors, that inexistent in the isotropic case.Comment: 4 pages, 3 figure

    Electric field effect modulation of transition temperature, mobile carrier density and in-plane penetration depth in NdBa2Cu3O(7-delta) thin films

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    We explore the relationship between the critical temperature, T_c, the mobile areal carrier density, n_2D, and the zero temperature magnetic in-plane penetration depth, lambda_ab(0), in very thin underdoped NdBa2Cu3O{7-delta} films near the superconductor to insulator transition using the electric field effect technique. We observe that T_c depends linearly on both, n_2D and lambda_ab(0), the signature of a quantum superconductor to insulator (QSI) transition in two dimensions with znu-bar where z is the dynamic and nu-bar the critical exponent of the in-plane correlation length.Comment: 4 pages, 4 figure

    The 110 watt per kilogram lightweight solar array system

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    This ultralightweight solar array system is applied to three generic mission types: (1) interplanetary, (2) geosynchronous, and (3) manned space station. The requirements of each of these missions, as they pertain to the solar array, are presented. Existing lightweight solar array system concepts are reviewed, along with conclusions regarding the applicability of this technology to the feasibility of the ultralightweight solar array system. Several system concepts are included for further evaluation. The existing technology base, as it pertains to solar cells, solar cell covers, interconnects and substrates, and deployable booms, is reviewed. The attitude control of spacecraft with large flexible solar arrays is also discussed
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