2,052 research outputs found
Excitations of the static quark-antiquark system in several gauge theories
The spectrum of gluons in the presence of a static quark-antiquark pair is
studied using Monte Carlo simulations on anisotropic space-time lattices. For
very small quark-antiquark separations R, the level orderings and approximate
degeneracies disagree with the expectations from an effective string theory. As
the quark-antiquark separation R increases, a dramatic rearrangement of the
energies occurs, and above 2 fm, all of the levels studied show behavior
consistent with an effective string description. The energy spacings are nearly
pi/R, but a tantalizing fine structure remains. In addition to 4-dimensional
SU(3) gauge theory, results from 3-dimensional SU(2) and compact U(1) gauge
theories are also presented.Comment: 12 pages, 4 figures, talk presented at the International Conference
on Color Confinement and Hadrons in Quantum Chromodynamics (Confinement
2003), RIKEN, July 21-24, 200
The heavy-quark hybrid meson spectrum in lattice QCD
Recent findings on the spectrum of heavy-quark mesons from computer
simulations of quarks and gluons in lattice QCD are summarized, with particular
attention to quark-antiquark states bound by an excited gluon field. The
validity of a Born-Oppenheimer treatment for such systems is discussed. Recent
results on glueball masses, the light-quark 1-+ hybrid meson mass, and the
static three-quark potential are summarized.Comment: 15 pages, 13 figures, talk given at the Workshop on Scalar Mesons: An
Interesting Puzzle for QCD, SUNY Institute of Technology, Utica, NY, May
16-18, 2003, submitted to American Institute of Physics Conference
Proceedings. After publication, it will be found at
http://proceedings.aip.org/proceedings
A Concert Hall for Albuquerque, New Mexico
The problem is to design a cultural center in Albuquerque consisting of an art museum and a concert hall. The problem requires the establishment of a location and and site planning of the massing relationship between the concert hall and the museum. Then, the concert hall is to be extracted for extensive development in design
Bacterial Quality of Private Water Wells in Clark County, Arkansas
Most private water wells in Clark County appeared to be contaminated by bacteria, apparently entering the wells from surface water seepage. Eighteen to 24% of the wells investigated were positive for fecal contamination. Deeper wells were less often contaminated. More than one-half of the wells sampled exceeded recommended limits of inorganic chemicals for safe potable water. High concentrations of iron and manganese were most common, exceeding recommended limits in more than 40% of the well
The Casimir Energy Paradox of the QCD String
It is widely thought that the early onset of the asymptotic Casimir energy
with unit conformal charge signals bosonic string formation of the confining
flux connecting a static quark-antiquark pair in QCD. This is observed on a
scale where most of the string eigenmodes do not exist and the few stable modes
above the ground state are displaced. Hints for the resolution of this paradox
are suggested.Comment: Lattice2003(topology
Location-Quality-aware Policy Optimisation for Relay Selection in Mobile Networks
Relaying can improve the coverage and performance of wireless access
networks. In presence of a localisation system at the mobile nodes, the use of
such location estimates for relay node selection can be advantageous as such
information can be collected by access points in linear effort with respect to
number of mobile nodes (while the number of links grows quadratically).
However, the localisation error and the chosen update rate of location
information in conjunction with the mobility model affect the performance of
such location-based relay schemes; these parameters also need to be taken into
account in the design of optimal policies. This paper develops a Markov model
that can capture the joint impact of localisation errors and inaccuracies of
location information due to forwarding delays and mobility; the Markov model is
used to develop algorithms to determine optimal location-based relay policies
that take the aforementioned factors into account. The model is subsequently
used to analyse the impact of deployment parameter choices on the performance
of location-based relaying in WLAN scenarios with free-space propagation
conditions and in an measurement-based indoor office scenario.Comment: Accepted for publication in ACM/Springer Wireless Network
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