318 research outputs found
Computer simulation of the pure and defective surface properties of -aluminium oxide, lanthanum cuprate and neodymium cuprate
Proton lifetime bounds from chirally symmetric lattice QCD
We present results for the matrix elements relevant for proton decay in Grand
Unified Theories (GUTs). The calculation is performed at a fixed lattice
spacing a^{-1}=1.73(3) GeV using 2+1 flavors of domain wall fermions on
lattices of size 16^3\times32 and 24^3\times64 with a fifth dimension of length
16. We use the indirect method which relies on an effective field theory
description of proton decay, where we need to estimate the low energy
constants, \alpha = -0.0112(25) GeV^3 and \beta = 0.0120(26) GeV^3. We relate
these low energy constants to the proton decay matrix elements using leading
order chiral perturbation theory. These can then be combined with experimental
bounds on the proton lifetime to bound parameters of individual GUTs.Comment: 17 pages, 9 Figure
Multimission Aircraft Fuel-Burn Minimization via Multipoint Aerostructural Optimization
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140677/1/1.J052940.pd
Development of Flutter Constraints for High-fidelity Aerostructural Optimization
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143080/1/6.2017-4455.pd
Quenched QCD with O(a) improvement: I. The spectrum of light hadrons
We present a comprehensive study of the masses of pseudoscalar and vector
mesons, as well as octet and decuplet baryons computed in O(a) improved
quenched lattice QCD. Results have been obtained using the non-perturbative
definition of the improvement coefficient c_sw, and also its estimate in
tadpole improved perturbation theory. We investigate effects of improvement on
the incidence of exceptional configurations, mass splittings and the parameter
J. By combining the results obtained using non-perturbative and tadpole
improvement in a simultaneous continuum extrapolation we can compare our
spectral data to experiment. We confirm earlier findings by the CP-PACS
Collaboration that the quenched light hadron spectrum agrees with experiment at
the 10% level.Comment: 36 pages, 7 postscript figures, REVTEX; typo in Table XVIII
corrected; extended discussion of finite-size effects in sections III and
VII; version to appear in Phys. Rev.
The Hyperfine Splitting in Charmonium: Lattice Computations Using the Wilson and Clover Fermion Actions
We compute the hyperfine splitting on the lattice,
using both the Wilson and -improved (clover) actions for quenched quarks.
The computations are performed on a lattice at ,
using the same set of 18 gluon configurations for both fermion actions. We find
that the splitting is 1.83\err{13}{15} times larger with the clover action than
with the Wilson action, demonstrating the sensitivity of the spin-splitting to
the magnetic moment term which is present in the clover action. However, even
with the clover action the result is less than half of the physical
mass-splitting. We also compute the decay constants and
, both of which are considerably larger when computed using
the clover action than with the Wilson action. For example for the ratio
we find 0.32\err{1}{2} with the Wilson action
and with the clover action (the physical value is 0.44(2)).Comment: LaTeX file, 8 pages and two postscript figures. Southampton Preprint:
SHEP 91/92-27 Edinburgh Preprint: 92/51
Gauge Invariant Smearing and Matrix Correlators using Wilson Fermions at beta=6.2
We present an investigation of gauge invariant smearing for Wilson fermions
on a lattice at . We demonstrate a smearing
algorithm that allows a substantial improvement in the determination of the
baryon spectrum obtained using propagators smeared at both source and sink, at
only a small computational cost. We investigate the matrix of correlators
constructed from local and smeared operators, and are able to expose excited
states of both the mesons and baryons.Comment: at lattice `92. 4 pages latex + 3 postscript figures. Edinburgh
preprint: 92/51
The Status of Lattice Calculations of the Nucleon Structure Functions
We review our progress on the lattice calculation of low moments of both the
unpolarised and polarised nucleon structure functions.Comment: 6 pages, contribution to 29th International Symposium on the Theory
of Elementary Particles, Buckow, Germany, (29 August - 2 September 1995). 6
pages, Latex, requires espcrc2.sty, epsf.st
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