8,324 research outputs found
An experiment to detect gravity at sub-mm scale with high-Q mechanical oscillators
Silicon double paddle oscillators are well suited for the detection of weak
forces because of their high Q factor (about 10^5 at room temperature). We
describe an experiment aimed at the detection of gravitational forces between
masses at sub-mm distance using such an oscillator. Gravitational excitation is
produced by a rotating aluminium disk with platinum segments. The force
sensitivity of this apparatus is about 10 fN at room temperature for 1000 s
averaging time at room temperature. The current limitations to detection of the
gravitational force are mentioned.Comment: 19 pages, to appear in Proceedings of the Tenth Marcel Grossmann
Meeting on General Relativity, edited by M. Novello, S. Perez-Bergliaffa and
R. Ruffini, World Scientific. Revision: portable format and revised figure
Evaluation of Packing_3D Code for Design of Variable-Depth, Bent-Chamber Acoustic Liners
Increases in the bypass ratio for commercial aircraft engines have caused the broadband fan noise component to become dominant. As a result, there is a need to develop improved acoustic liners suitable for absorption of this fan noise over a wide frequency range, preferably up to at least two octaves. Variable depth liners with bent chambers and three-dimensional geometries present one way to achieve this goal, however, they can be difficult and time-consuming to design due to their complexity and volume constraints. A packing code, called Packing3D, has been developed that automatically designs the chamber configurations of such liners once the chamber dimensions and volume constraints are known. The code uses a randomized trial and error approach to place each chamber in a representation of the liner sample, then returns a colored diagram and sufficient information for the liner sample to be fabricated. For evaluation, the code is used to design four liner samples of varying levels of complexity. These samples are tested with and without a mesh facesheet in the NASA Langley Normal Incidence Tube, and the results are compared to predictions computed in COMSOL. The results indicate that the packing code is able to quickly design samples that are predictable, achieve the desired absorption spectrum, fit the given constraints, and are able to be built. This code is flexible, lends itself to optimization, and allows samples to be designed quickly, accurately, and efficiently
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
Two-point functions of quenched lattice QCD in Numerical Stochastic Perturbation Theory
We summarize the higher-loop perturbative computation of the ghost and gluon
propagators in SU(3) Lattice Gauge Theory. Our final aim is to compare with
results from lattice simulations in order to expose the genuinely
non-perturbative content of the latter. By means of Numerical Stochastic
Perturbation Theory we compute the ghost and gluon propagators in Landau gauge
up to three and four loops. We present results in the infinite volume and limits, based on a general fitting strategy.Comment: 3 pages, 5 figures, talk at conference QCHS-IX, Madrid 201
Two-point functions of quenched lattice QCD in Numerical Stochastic Perturbation Theory. (I) The ghost propagator in Landau gauge
This is the first of a series of two papers on the perturbative computation
of the ghost and gluon propagators in SU(3) Lattice Gauge Theory. Our final aim
is to eventually compare with results from lattice simulations in order to
enlight the genuinely non-perturbative content of the latter. By means of
Numerical Stochastic Perturbation Theory we compute the ghost propagator in
Landau gauge up to three loops. We present results in the infinite volume and
limits, based on a general strategy that we discuss in detail.Comment: 27 pages, 11 figure
A Lattice Evaluation of the Deep-Inelastic Structure Functions of the Nucleon
The lower moments of the unpolarized and polarized deep-inelastic structure
functions of the nucleon are calculated on the lattice. The calculation is done
with Wilson fermions and for three values of the hopping parameter , so
that we can perform the extrapolation to the chiral limit. Particular emphasis
is put on the renormalization of lattice operators. The renormalization
constants, which lead us from lattice to continuum operators, are computed
perturbatively to one loop order as well as non-perturbatively.Comment: 11 pages, uuencoded postscript file. Talk given at Workshop QCD on
Massively Parallel Computers, Yamagata, March 1995. Also available from
http://www.desy.de/pub/preprints/desy/199
The lattice ghost propagator in Landau gauge up to three loops using Numerical Stochastic Perturbation Theory
We complete our high-accuracy studies of the lattice ghost propagator in
Landau gauge in Numerical Stochastic Perturbation Theory up to three loops. We
present a systematic strategy which allows to extract with sufficient precision
the non-logarithmic parts of logarithmically divergent quantities as a function
of the propagator momentum squared in the infinite-volume and limits.
We find accurate coincidence with the one-loop result for the ghost self-energy
known from standard Lattice Perturbation Theory and improve our previous
estimate for the two-loop constant contribution to the ghost self-energy in
Landau gauge. Our results for the perturbative ghost propagator are compared
with Monte Carlo measurements of the ghost propagator performed by the Berlin
Humboldt university group which has used the exponential relation between
potentials and gauge links.Comment: 8 pages, 6 figures, XXVII International Symposium on Lattice Field
Theory - LAT2009, Beijin
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