11,461 research outputs found
Parton and Hadron Correlations in Jets
Correlation between shower partons is first studied in high jets. Then
in the framework of parton recombination the correlation between pions in
heavy-ion collisions is investigated. Since thermal partons play very different
roles in central and peripheral collisions, it is found that the correlation
functions of the produced hadrons behave very differently at different
centralities, especially at intermediate . The correlation function that
can best exhibit the distinctive features is suggested. There is not a great
deal of overlap between what we can calculate and what has been measured.
Nevertheless, some aspects of our results compare favorably with experimental
data.Comment: 28 pages in Latex + 13 figures. This is a revised version with
extended discussions added without quantitative changes in the result
Hourly Variability in Q0957+561
We have continued our effort to re-reduce archival Q0957+561 brightness
monitoring data and present results for 1629 R-band images using the methods
for galaxy subtraction and seeing correction reported previously. The new
dataset comes from 4 observing runs, several nights apiece, with sampling of
typically 5 minutes, which allows the first measurement of the structure
function for variations in the R-band from timescales of hours to years.
Comparison of our reductions to previous reductions of the same data, and to
r-band photometry produced at Apache Point Observatory shows good overall
agreement. Two of the data runs, separated by 417 days, permit a sharpened
value for the time delay of 417.4 days, valid only if the time delay is close
to the now-fashionable 417-day value; our data do not constrain a delay if it
is more than three days from this 417-day estimate. Our present results show no
unambiguous signature of the daily microlensing, though a suggestive feature is
found in the data. Both time delay measurement and microlensing searches suffer
from from the lack of sampling at half-day offsets, inevitable at a single
observatory, hence the need for round-the-clock monitoring with participation
by multiple observatories.Comment: AASTeX 4.0 preprint style, 21 pages, 8 EPS figure
Loss tolerant linear optical quantum memory by measurement-based quantum computing
We give a scheme for loss tolerantly building a linear optical quantum memory which itself is tolerant to qubit loss. We use the encoding recently introduced in Varnava et al 2006 Phys. Rev. Lett. 97 120501, and give a method for efficiently achieving this. The entire approach resides within the 'one-way' model for quantum computing (Raussendorf and Briegel 2001 Phys. Rev. Lett. 86 5188–91; Raussendorf et al 2003 Phys. Rev. A 68 022312). Our results suggest that it is possible to build a loss tolerant quantum memory, such that if the requirement is to keep the data stored over arbitrarily long times then this is possible with only polynomially increasing resources and logarithmically increasing individual photon life-times
Ridge Formation Induced by Jets in Collisions at 7 TeV
An interpretation of the ridge phenomenon found in pp collisions at 7 TeV is
given in terms of enhancement of soft partons due to energy loss of semihard
jets. A description of ridge formation in nuclear collisions can directly be
extended to pp collisions, since hydrodynamics is not used, and azimuthal
anisotropy is generated by semihard scattering. Both the p_T and multiplicity
dependencies are well reproduced. Some suggestions are made about other
observables.Comment: Expanded version to be published in Phys. Rev.
Poisson smooth structures on stratified symplectic spaces
In this paper we introduce the notion of a smooth structure on a stratified
space, the notion of a Poisson smooth structure and the notion of a weakly
symplectic smooth structure on a stratified symplectic space, refining the
concept of a stratified symplectic Poisson algebra introduced by Sjamaar and
Lerman. We show that these smooth spaces possess several important properties,
e.g. the existence of smooth partitions of unity. Furthermore, under mild
conditions many properties of a symplectic manifold can be extended to a
symplectic stratified space provided with a smooth Poisson structure, e.g. the
existence and uniqueness of a Hamiltonian flow, the isomorphism between the
Brylinski-Poisson homology and the de Rham homology, the existence of a
Leftschetz decomposition on a symplectic stratified space. We give many
examples of stratified symplectic spaces possessing a Poisson smooth structure
which is also weakly symplectic.Comment: 21 page, final version, to appear in the Proceedings of the 6-th
World Conference on 21st Century Mathematic
Interpretation of F106B and CV580 in-flight lightning data and form factor determination
Two topics of in-flight aircraft/lightning interaction are addressed. The first is the analysis of measured data from the NASA F106B Thunderstorm Research Aircraft and the CV580 research program run by the FAA and Wright-Patterson Air Force Base. The CV580 data was investigated in a mostly qualitative sense, while the F106B data was subjected to both statistical and quantitative analysis using linear triggered lightning finite difference models. The second main topic is the analysis of field mill data and the calibration of the field mill systems. The calibration of the F106B field mill system was investigated using an improved finite difference model of the aircraft having a spatial resolution of one-quarter meter. The calibration was applied to measured field mill data acquired during the 1985 thunderstorm season. The experimental determination of form factors useful for field mill calibration was also investigated both experimentally and analytically. The experimental effort involved the use of conducting scale models and an electrolytic tank. An analytic technique was developed to aid in the understanding of the experimental results
Direct current superconducting quantum interferometers with asymmetric shunt resistors
We have investigated asymmetrically shunted Nb/Al-AlO/Nb direct current
(dc) superconducting quantum interference devices (SQUIDs). While keeping the
total resistance identical to a comparable symmetric SQUID with , we shunted only one of the two Josephson junctions with
. Simulations predict that the optimum energy resolution
and thus also the noise performance of such an asymmetric SQUID can
be 3--4 times better than that of its symmetric counterpart. Experiments at a
temperature of 4.2\,K yielded for an asymmetric
SQUID with an inductance of . For a comparable symmetric device
was achieved, confirming our simulation results.Comment: 5 pages, 4 figure
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