6,953 research outputs found
Scaling of Non-Perturbatively O(a) Improved Wilson Fermions: Hadron Spectrum, Quark Masses and Decay Constants
We compute the hadron mass spectrum, the quark masses and the meson decay
constants in quenched lattice QCD with non-perturbatively improved
Wilson fermions. The calculations are done for two values of the coupling
constant, and 6.2, and the results are compared with the
predictions of ordinary Wilson fermions. We find that the improved action
reduces lattice artifacts as expected
The SU(3) Beta Function from Numerical Stochastic Perturbation Theory
The SU(3) beta function is computed from Wilson loops to 20th order numerical
stochastic perturbation theory. An attempt is made to include massless
fermions, whose contribution is known analytically to 4th order. The question
whether the theory admits an infrared stable fixed point is addressed.Comment: 10 pages, 7 figures, version to be published in Physics Letters
Test of constancy of speed of light with rotating cryogenic optical resonators
A test of Lorentz invariance for electromagnetic waves was performed by
comparing the resonance frequencies of two optical resonators as a function of
orientation in space. In terms of the Robertson-Mansouri-Sexl theory, we obtain
, a ten-fold improvement compared to
the previous best results. We also set a first upper limit for a so far unknown
parameter of the Standard Model Extension test theory,
.Comment: 4 pages, 2 figures, accepted for publication Phys. Rev. A (2005
Behavior in normal and reduced gravity of an enclosed liquid/gas system with nonuniform heating from above
The temperature and velocity fields have been investigated for a single-phase gas system and a two-layer gas-and-liquid system enclosed in a circular cylinder being heated suddenly and nonuniformly from above. The transient response of the gas, liquid, and container walls was modelled numerically in normal and reduced gravity (10 to the -5 g). Verification of the model was accomplished via flow visualization experiments in 10 cm high by 10 cm diameter plexiglass cylinders
Projecting the Kondo Effect: Theory of the Quantum Mirage
A microscopic theory is developed for the projection (quantum mirage) of the
Kondo resonance from one focus of an elliptic quantum corral to the other
focus. The quantum mirage is shown to be independent of the size and the shape
of the ellipse, and experiences \lambda_F/4 oscillations (\lambda_F is the
surface-band Fermi wavelength) with an increasing semimajor axis length. We
predict an oscillatory behavior of the mirage as a function of a weak magnetic
field applied perpendicular to the sample.Comment: 4 pages 2 figures include
Non-Perturbative versus Perturbative Renormalization of Lattice Operators
Our objective is to compute the moments of the deep-inelastic structure
functions of the nucleon on the lattice. A major source of uncertainty is the
renormalization of the lattice operators that enter the calculation. In this
talk we compare the renormalization constants of the most relevant twist-two
bilinear quark operators which we have computed non-perturbatively and
perturbatively to one loop order. Furthermore, we discuss the use of tadpole
improved perturbation theory.Comment: 4 pages, uuencoded postscript file. Contribution to Lattice 95. Also
available from http://www.desy.de/pub/preprints/desy/199
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