61,232 research outputs found
The radial distributions of a heavy-light meson on a lattice
In an earlier work, the charge (vector) and matter (scalar) radial
distributions of heavy-light mesons were measured in the quenched approximation
on a 16^3 times 24 lattice with a quark-gluon coupling of 5.7, a lattice
spacing of 0.17 fm, and a hopping parameter corresponding to a light quark mass
about that of the strange quark.
Several improvements are now made: 1) The configurations are generated using
dynamical fermions with a quark-gluon coupling of 5.2 (a lattice spacing of
0.14 fm); 2) Many more gauge configurations are included (78 compared with the
earlier 20); 3) The distributions at many off-axis, in addition to on-axis,
points are measured; 4) The data-analysis is much more complete. In particular,
distributions involving excited states are extracted.
The exponential decay of the charge and matter distributions can be described
by mesons of mass 0.9+-0.1 and 1.5+-0.1 GeV respectively - values that are
consistent with those of vector and scalar qqbar-states calculated directly
with the same lattice parameters.Comment: 3 pages, 4 figures, Lattice2002(heavyquark
A Classical Manifestation of the Pauli Exclusion Principle
The occupied and unoccupied fermionic BPS quantum states of a type-IIA string
stretched between a D6-brane and an orthogonal D2-brane are described in
M-theory by two particular holomorphic curves embedded in a Kaluza-Klein
monopole. The absence of multiply-occupied fermionic states --- the Pauli
exclusion principle --- is manifested in M-theory by the absence of any other
holomorphic curves satisfying the necessary boundary conditions. Stable,
non-BPS states with multiple strings joining the D6-brane and D2-brane are
described M-theoretically by non-holomorphic curves.Comment: harvmac 6 pages. Final version as published in JHE
Curvature terms in D-brane actions and their M-theory origin
We derive the complete terms of effective D-brane actions,
for arbitrary ambient geometries and world-volume embeddings, at lowest order
(disk-level) in the string-loop expansion. These terms reproduce the
corrections to string scattering amplitudes, and are consistent
with duality conjectures. In the particular case of the D3-brane with trivial
normal bundle, considerations of invariance lead to a
complete sum of D-instanton corrections for both the parity-conserving and the
parity-violating parts of the effective action. These corrections are required
for the cancellation of the modular anomalies of massless modes, and are
consistent with the absence of chiral anomalies in the intersection domain of
pairs of D-branes. We also show that the parity-conserving part of the
non-perturbative R^2 action follows from a one-loop quantum calculation in the
six-dimensional world-volume of the M5-brane compactified on a two-torus.Comment: tex file, 31 pages, uses harvmac. Some rewriting of section 2,
conclusions and appendix B, in particular in what concerns the discussion of
seven-branes in the conclusions and the structure of terms in
appendix B. Other minor corrections plus added reference
Flux-tube Structure, Sum Rules and Beta-functions in SU(2)
Action and energy flux-tube profiles are computed, in SU(2) with
beta=2.4,2.5, for two quarks up to 1 fm apart and for which the colour fields
are in their ground state (A_1g) and the first (E_u) and higher (A'_1g) excited
gluonic states. When these profiles are integrated over all space, a scaling
comparison is made between the beta=2.4 and 2.5 data. Using sum rules, these
integrated forms also permit an estimate to be made of generalised
beta-functions giving b(2.4)=-0.312(15), b(2.5)=-0.323(9), f(2.4)=0.65(1) and
f(2.5)=0.68(1). When the profiles are integrated only over planes transverse to
the interquark line and assuming underlying string features, scaling
comparisons are again made near the centres of the interquark line for the
largest interquark distances. For the A'_{1g} case, some of the profiles
exhibit a 'dip-like' structure characteristic of the Isgur-Paton model.Comment: 3 pages, 6 eps figures. Presented at LATTICE9
Four-quark flux distribution and binding in lattice SU(2)
The full spatial distribution of the color fields of two and four static
quarks is measured in lattice SU(2) field theory at separations up to 1 fm at
beta=2.4. The four-quark case is equivalent to a qbar q qbar q system in SU(2)
and is relevant to meson-meson interactions. By subtracting two-body flux tubes
from the four-quark distribution we isolate the flux contribution connected
with the four-body binding energy. This contribution is further studied using a
model for the binding energies. Lattice sum rules for two and four quarks are
used to verify the results.Comment: 46 pages including 71 eps figures. 3D color figures are available at
www.physics.helsinki.fi/~ppennane/pics
Flight prototype regenerative particulate filter system development
The effort to design, fabricate, and test a flight prototype Filter Regeneration Unit used to regenerate (clean) fluid particulate filter elements is reported. The design of the filter regeneration unit and the results of tests performed in both one-gravity and zero-gravity are discussed. The filter regeneration unit uses a backflush/jet impingement method of regenerating fluid filter elements that is highly efficient. A vortex particle separator and particle trap were designed for zero-gravity use, and the zero-gravity test results are discussed. The filter regeneration unit was designed for both inflight maintenance and ground refurbishment use on space shuttle and future space missions
FARM LEVEL IRRIGATION TECHNOLOGY DECISIONS OVER TIME
A time-series cross-sectional model of irrigation technology choice is developed for an irrigation district in California's Central Valley to show how changes in the relative price of irrigation water and variations in water supply over time influence the choice of irrigation system. Results indicate changes in crop mix and variations in water supply are at least as important as price in determining the choice of irrigation system.Farm Management,
Interactions of heavy-light mesons
The potential between static-light mesons forming a meson-meson or a
meson-antimeson system is calculated in quenched and unquenched SU(3) gauge
theory. We use the Sheikholeslami-Wohlert action and statistical estimators of
light quark propagators with maximal variance reduction. The dependence of the
potentials on the light quark spin and isospin and the effect of meson exchange
is investigated. Our main motivation is exploration of bound states of two
mesons and string breaking. The latter also involves the two-quark potential
and the correlation between two-quark and two-meson states.Comment: Contribution to LATTICE99 (QCD spectrum). 3 pages, 4 eps figure
THE IMPORTANCE OF TARIFF STRUCTURE IN CONSERVATION PRICING
Resource /Energy Economics and Policy,
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