134 research outputs found

    Feno e silagem como volumoso para confinamento de bovinos de corte.

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    bitstream/item/67190/1/CT-49-2001.pd

    Experimentação em rede de genótipos de trigo para duplo propósito no Rio Grande do Sul em 2000.

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    bitstream/item/84111/1/CNPT-BOL.-PESQ.-5-01.pd

    Experimentação de trigo para duplo propósito no Rio Grande do Sul, em 1999.

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    bitstream/item/84110/1/CNPT-BOL.-PESQ.-5-00.pd

    Multi-Regge kinematics and the moduli space of Riemann spheres with marked points

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    We show that scattering amplitudes in planar N = 4 Super Yang-Mills in multi-Regge kinematics can naturally be expressed in terms of single-valued iterated integrals on the moduli space of Riemann spheres with marked points. As a consequence, scattering amplitudes in this limit can be expressed as convolutions that can easily be computed using Stokes' theorem. We apply this framework to MHV amplitudes to leading-logarithmic accuracy (LLA), and we prove that at L loops all MHV amplitudes are determined by amplitudes with up to L + 4 external legs. We also investigate non-MHV amplitudes, and we show that they can be obtained by convoluting the MHV results with a certain helicity flip kernel. We classify all leading singularities that appear at LLA in the Regge limit for arbitrary helicity configurations and any number of external legs. Finally, we use our new framework to obtain explicit analytic results at LLA for all MHV amplitudes up to five loops and all non-MHV amplitudes with up to eight external legs and four loops.Comment: 104 pages, six awesome figures and ancillary files containing the results in Mathematica forma

    Mellin Amplitudes for Dual Conformal Integrals

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    Motivated by recent work on the utility of Mellin space for representing conformal correlators in AdSAdS/CFT, we study its suitability for representing dual conformal integrals of the type which appear in perturbative scattering amplitudes in super-Yang-Mills theory. We discuss Feynman-like rules for writing Mellin amplitudes for a large class of integrals in any dimension, and find explicit representations for several familiar toy integrals. However we show that the power of Mellin space is that it provides simple representations even for fully massive integrals, which except for the single case of the 4-mass box have not yet been computed by any available technology. Mellin space is also useful for exhibiting differential relations between various multi-loop integrals, and we show that certain higher-loop integrals may be written as integral operators acting on the fully massive scalar nn-gon in nn dimensions, whose Mellin amplitude is exactly 1. Our chief example is a very simple formula expressing the 6-mass double box as a single integral of the 6-mass scalar hexagon in 6 dimensions.Comment: 29+7 page

    Analytic properties of high energy production amplitudes in N=4 SUSY

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    We investigate analytic properties of the six point planar amplitude in N=4 SUSY at the multi-Regge kinematics for final state particles. For inelastic processes the Steinmann relations play an important role because they give a possibility to fix the phase structure of the Regge pole and Mandelstam cut contributions. These contributions have the Moebius invariant form in the transverse momentum subspace. The analyticity and factorization constraints allow us to reproduce the two-loop correction to the 6-point BDS amplitude in N=4 SUSY obtained earlier in the leading logarithmic approximation with the use of the s-channel unitarity. The exponentiation hypothesis for the remainder function in the multi-Regge kinematics is also investigated. The 6-point amplitude in LLA can be completely reproduced from the BDS ansatz with the use of the analyticity and Regge factorization.Comment: To appear in the proceedings of 16th International Seminar on High Energy Physics, QUARKS-2010, Kolomna, Russia, 6-12 June, 2010. 15 page
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