803 research outputs found
The Export Trading Company Act of 1982 and the photovoltaics industry: An assessment
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
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++
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
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
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
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
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
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
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) transition in
CO 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 .Comment: Submitted to Physical Review Letter
On the theoretical uncertainties in the muon anomalous magnetic moment
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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