3,066 research outputs found

    Skewed distributions fixed by diagonal partons at small x,\xi and γpVp\gamma^* p \to Vp at HERA

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    We show that the skewed parton distributions are completely determined at small x and \xi by the conventional diagonal partons. We study the application to diffractive vector meson production at HERA.Comment: 3 pages, LATeX, no figures, uses npb.sty, presented at the DIS99 Workshop, Zeuthen, Germany, April 19-23, 1999, to appear in the proceeding

    The CantiClever: a dedicated probe for magnetic force microscopy

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    We present a new cantilever for magnetic-force microscopy (MFM), the CantiClever, which is not derived from atomic-force microscopy (AFM) probes but optimized for MFM. Our design integrates the cantilever and the magnetic tip in a single manufacturing process with the use of silicon micromachining techniques, which allows for batch fabrication of the probes. This manufacturing process enables precise control on all dimensions of the magnetic tip, resulting in a very thin magnetic element with a very high aspect ratio. Using. the CantiClever, magnetic features down to 30 nm could be observed in a CAMST reference sample

    Vanadium, an element required by animals but not by plants

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    Wave scattering by small bodies and creating materials with a desired refraction coefficient

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    Asymptotic solution to many-body wave scattering problem is given in the case of many small scatterers. The small scatterers can be particles whose physical properties are described by the boundary impedances, or they can be small inhomogeneities, whose physical properties are described by their refraction coefficients. Equations for the effective field in the limiting medium are derived. The limit is considered as the size aa of the particles or inhomogeneities tends to zero while their number M(a)M(a) tends to infinity. These results are applied to the problem of creating materials with a desired refraction coefficient. For example, the refraction coefficient may have wave-focusing property, or it may have negative refraction, i.e., the group velocity may be directed opposite to the phase velocity. This paper is a review of the author's results presented in MR2442305 (2009g:78016), MR2354140 (2008g:82123), MR2317263 (2008a:35040), MR2362884 (2008j:78010), and contains new results.Comment: In this paper the author's invited plenary talk at the 7-th PACOM (PanAfrican Congress of Mathematicians), is presente

    Searching for a light Fermiophobic Higgs Boson at the Tevatron

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    We propose new production mechanisms for light fermiophobic Higgs bosons (hfh_f) with suppressed couplings to vector bosons (VV) at the Fermilab Tevatron. These mechanisms (e.g. qqH±hfqq'\to H^\pm h_f) are complementary to the conventional process qqVhfqq'\to Vh_f, which suffers from a strong suppression of 1/tan2β1/\tan^2\beta in realistic models with a hfh_f. The new mechanisms extend the coverage at the Tevatron Run II to the larger tanβ\tan\beta region, and offer the possibility of observing new event topologies with up to 4 photons.Comment: 15 pages, including 5 eps-figure

    A class of quasicontractive semigroups acting on Hardy and Dirichlet space

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    This paper provides a complete characterization of quasicontractive C0-semigroups on Hardy and Dirichlet space with a prescribed generator of the form Af = Gf ′. We show that such semigroups are semigroups of composition operators, and we give simple sufficient and necessary condition on G. Our techniques are based on ideas from semigroup theory, such as the use of numerical ranges

    Scattering of electromagnetic waves by many thin cylinders: theory and computational modeling

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    Electromagnetic (EM) wave scattering by many parallel infinite cylinders is studied asymptotically as a tends to 0, where a is the radius of the cylinders. It is assumed that the centres of the cylinders are distributed so that their numbers is determined by some positive function N(x). The function N(x) >= 0 is a given continuous function. An equation for the self-consistent (limiting) field is derived as a tends to 0. The cylinders are assumed perfectly conducting. Formula for the effective refraction coefficient of the new medium, obtained by embedding many thin cylinders into a given region, is derived. The numerical results presented demonstrate the validity of the proposed approach and its efficiency for solving the many-body scattering problems, as well as the possibility to create media with negative refraction coefficients.Comment: 21 pages, 13 figure
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