496 research outputs found
RANS-based Aerodynamic Shape Optimization of a Blended-Wing-Body Aircraft
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106453/1/AIAA2013-2586.pd
Lattice QCD with mixed actions
We discuss some of the implications of simulating QCD when the action used
for the sea quarks is different from that used for the valence quarks. We
present exploratory results for the hadron mass spectrum and pseudoscalar meson
decay constants using improved staggered sea quarks and HYP-smeared overlap
valence quarks. We propose a method for matching the valence quark mass to the
sea quark mass and demonstrate it on UKQCD clover data in the simpler case
where the sea and valence actions are the same.Comment: 15 pages, 10 figures some minor modification to text and figures.
Accepted for publicatio
Modeling Boundary Layer Ingestion Using a Coupled Aeropropulsive Analysis
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143109/1/1.C034601.pd
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
Current Renormalisation Constants with an O(a)-improved Fermion Action
Using chiral Ward identities, we determine the renormalisation constants of
bilinear quark operators for the Sheikholeslami-Wohlert action lattice at
beta=6.2. The results are obtained with a high degree of accuracy. For the
vector current renormalisation constant we obtain Z_V=0.817(2)(8), where the
first error is statistical and the second is due to mass dependence of Z_V.
This is close to the perturbative value of 0.83. For the axial current
renormalisation constant we obtain Z_A = 1.045(+10 -14), significantly higher
than the value obtained in perturbation theory. This is shown to reduce the
difference between lattice estimates and the experimental values for the
pseudoscalar meson decay constants, but a significant discrepancy remains. The
ratio of pseudoscalar to scalar renormalisation constants, Z_P/Z_S, is less
well determined, but seems to be slightly lower than the perturbative value.Comment: 8 pages uuencoded compressed postscript file. Article to be submitted
to Phys.Rev.
Light hadron spectroscopy with O(a) improved dynamical fermions
We present the first results for the static quark potential and the light
hadron spectrum using dynamical fermions at using an O(a) improved
Wilson fermion action together with the standard Wilson plaquette action for
the gauge part. Sea quark masses were chosen such that the pseudoscalar-vector
mass ratio, m_PS/m_V$, varies from 0.86 to 0.67. Finite-size effects are
studied by using three different volumes, 8^3\cdot 24, 12^3\cdot 24 and
16^3\cdot 24. Comparing our results to previous ones obtained using the
quenched approximation, we find evidence for sea quark effects in quantities
like the static quark potential and the vector-pseudoscalar hyperfine
splitting.Comment: 38 pages, 14 Postscript figure, LaTe
Light Hadron Spectrum in Quenched Lattice QCD with Staggered Quarks
Without chiral extrapolation, we achieved a realistic nucleon to (\rho)-meson
mass ratio of (m_N/m_\rho = 1.23 \pm 0.04 ({\rm statistical}) \pm 0.02 ({\rm
systematic})) in our quenched lattice QCD numerical calculation with staggered
quarks. The systematic error is mostly from finite-volume effect and the
finite-spacing effect is negligible. The flavor symmetry breaking in the pion
and (\rho) meson is no longer visible. The lattice cutoff is set at 3.63 (\pm)
0.06 GeV, the spatial lattice volume is (2.59 (\pm) 0.05 fm)(^3), and bare
quarks mass as low as 4.5 MeV are used. Possible quenched chiral effects in
hadron mass are discussed.Comment: 5 pages and 5 figures, use revtex
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
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