802 research outputs found

    The Export Trading Company Act of 1982 and the photovoltaics industry: An assessment

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    The potential advantages of recent export promotion legislation for the U.S. photovoltaics industry were assessed. The provisions of the Export Trading Company Act of 1982 were reviewed and the export trade sector was surveyed to determine what impact the Act is haviang on export company activity. The photovoltaics industry was then studied to determine whether the Act offers particular advantages for promoting its product overseas

    Four-loop moments of the heavy quark vacuum polarization function in perturbative QCD

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    New results at four-loop order in perturbative QCD for the first two Taylor coefficients of the heavy quark vacuum polarization function are presented. They can be used to perform a precise determination of the charm- and bottom-quark mass. Implications for the value of the quark masses are briefly discussed.Comment: 8 pages, 13 figures; final version accepted for publication in the journa

    Reduze - Feynman Integral Reduction in C++

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    Reduze is a computer program for reducing Feynman Integrals to master integrals employing a Laporta algorithm. The program is written in C++ and uses classes provided by the GiNaC library to perform the simplifications of the algebraic prefactors in the system of equations. Reduze offers the possibility to run reductions in parallel.Comment: 18 pages, 2 figure

    QCD Decoupling at Four Loops

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    We present the matching condition for the strong coupling contant alpha_s at a heavy quark threshold to four loops in the modified minimal subtraction scheme. Our results lead to further decrease of the theoretical uncertainty of the evolution of the strong coupling constant through heavy quark thresholds. Using a low energy theorem we furthermore derive the effective coupling of the Higgs boson to gluons (induced by a virtual heavy quark) in four- and (partially) through five-loop approximation.Comment: 21 pages, 2 figures, the complete paper is also available via the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints

    Standard and epsilon-finite Master Integrals for the rho-Parameter

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    We have constructed an epsilon-finite basis of master integrals for all new types of one-scale tadpoles which appear in the calculation of the four-loop QCD corrections to the electroweak rho-parameter. Using transformation rules from the epsilon-finite basis to the standard minimal-number-of-lines basis, we obtain as a by-product analytical expressions for few leading terms of the epsilon-expansion of all members of the standard basis. The new master integrals have been computed with the help of the Pade method and by use of difference equations independently.Comment: 26 page

    Characterization of femtosecond laser written waveguides for integrated biochemical sensing

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    Fluorescence detection is known to be one of the most sensitive among the different optical sensing techniques. This work focuses on excitation and detection of fluorescence emitted by DNA strands labeled with fluorescent dye molecules that can be excited at a specific wavelength. Excitation occurs via optical channel waveguides written with femtosecond laser pulses applied coplanar with a microfluidic channel on a glass chip. The waveguides are optically characterized in order to facilitate the design of sensing structures which can be applied for monitoring the spatial separation of biochemical\ud species as a result of capillary electrophoresis

    New Results in Four and Five Loop QED calculations

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    We report on two recent multiloop results in QED: (i) the four-loop corrections to the conversion relations between the QED charge renormalized in the on-shell and MS-bar schemes; (ii) analytical evaluation of a class of asymptotic contributions to the muon anomaly at five-loops.Comment: Talk presented at 9th DESY Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field Theory, Sondershausen, Germany, 20-25 April 200

    Recent progress in computing four-loop massive correlators

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    We report about recent progress in computing four-loop massive correlators. The expansion of these correlators in the external momentum leads to vacuum integrals. The calculation of these vacuum integrals can be used to determine Taylor expansion coefficients of the vacuum polarization function and decoupling functions in perturbative Quantum chromodynamics. New results at four-loop order for the lowest Taylor expansion coefficient of the vacuum polarization function and for the decoupling relation are presented.Comment: 4 pages, talk given at the 12th International Conference on Quantum Chromodynamics, Montpellier, 4-8th July 200

    Primary gas thermometry by means of laser-absorption spectroscopy: Determination of the Boltzmann constant

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    We report on a new optical implementation of primary gas thermometry based on laser absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) ν1+2ν210+ν3\nu_{1} + 2 \nu_{2}^{\phantom{1}0} + \nu_{3} transition in CO2_{2} gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of 1.6×104\sim1.6\times10^{-4}.Comment: Submitted to Physical Review Letter

    On the theoretical uncertainties in the muon anomalous magnetic moment

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    I present a fairly detailed discussion of various contributions to the anomalous magnetic moment of the muon a_mu. I try to give an unbiased evaluation of the validity of the SM prediction for this quantity and to point out some delicate issues involved in its calculation. I conclude that the theory uncertainties in the SM prediction for the muon anomalous magnetic moment are underestimated and a great deal of work will be required to reduce these uncertainties to the level required by experiment.Comment: 12 pages, revte
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