11,294 research outputs found
Charge Superselection Sectors for Scalar QED on the Lattice
The lattice model of scalar quantum electrodynamics (Maxwell field coupled to
a complex scalar field) in the Hamiltonian framework is discussed.
It is shown that the algebra of observables of this
model is a -algebra, generated by a set of gauge-invariant elements
satisfying the Gauss law and some additional relations. Next, the faithful,
irreducible and non-degenerate representations of are
found. They are labeled by the value of the total electric charge, leading to a
decomposition of the physical Hilbert space into charge superselection sectors.
In the Appendices we give a unified description of spinorial and scalar quantum
electrodynamics and, as a byproduct, we present an interesting example of
weakly commuting operators, which do not commute strongly
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
Centrality Scaling of the Distribution of Pions
From the preliminary data of PHENIX on the centrality dependence of the
spectrum in at midrapidity in heavy-ion collisions, we show that
a scaling behavior exists that is independent of the centrality. It is then
shown that degrades with increasing exponentially with a
decay constant that can be quantified. A scaling distribution in terms of an
intuitive scaling variable is derived that is analogous to the KNO scaling. No
theoretical models are used in any part of this phenomenological analysis.Comment: 4 pages RevTex, 5 figures include
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.
Critical Fluctuation of Wind Reversals in Convective Turbulence
The irregular reversals of wind direction in convective turbulence are found
to have fluctuating intervals that can be related to critical behavior. It is
shown that the net magnetization of a 2D Ising lattice of finite size
fluctuates in the same way. Detrended fluctuation analysis of the wind reversal
time series results in a scaling behavior that agrees with that of the Ising
problem. The properties found suggest that the wind reversal phenomenon
exhibits signs of self-organized criticality.Comment: 4 RevTeX pages + 3 figures in ep
Dihadron Correlation in Jets Produced in Heavy-Ion Collisions
The difference between the structures of jets produced in heavy-ion and
hadronic collisions can best be exhibited in the correlations between particles
within those jets. We study the dihadron correlations in jets in the framework
of parton recombination. Two types of triggers, and proton, are
considered. It is shown that the recombination of thermal and shower partons
makes the most important contribution to the spectra of the associated
particles at intermediate . In collisions the only significant
contribution arises from shower-shower recombination, which is negligible in
heavy-ion collisions. Moments of the associated-particle distributions are
calculated to provide simple summary of the jet structures for easy comparison
with experiments.Comment: 24 pages in Latex + 5 figure
Efficiency of supplementing saccharomyces cerevisiae var. ellipsoideus for improved growth performance and carcass yield in broilers
The use of dietary additives is becoming a very interesting practise to improve animal health and performance in poultry production. Thepax® is a prebiotic that includes inactivated Saccharomyces cerevisiae Var. ellipsoideus cells and nutrients such as vitamins, enzymes, amino acids and short chain polypeptides. The effects of supplementing diet by Thepax® via potable water on growth and carcass yield were studied in broilers. Two treatments, an active with Thepax® and a control treatment, were used on 120 male and female chicks of the Hubbard JV breed. Birds were divided into 6 groups of 20 birds each managed on floor and received the same starter, grower and finisher concentrates based on maize and soybean meal during a 37 days trial period. Thepax®(0.5 ml of the additive for 1 litre of water) was used during only one month. Body weight and daily growth rate seemed to increase by 6.2% and 6.4%, respectively, in birds receiving Thepax® compared to control birds. Feed conversion ratio and water intake were similar (P≥0.201) for both groups of birds. The effect of the additive was important on birds’ health. The mortality rate decreased (P=0.0241) by around 71% in birds receiving Thepax®compared to that in control birds. Furthermore, the active group of birds deposited (P = 0.0172) less abdominal fat (-35.2%) without affecting carcass yield. Positive effects of Thepax® with its structure and composition may be an important additional source of nutrients supports growth and enhance feed ingredients digestibility and beneficial intestinal microflora activity in broilers. In conclusion, Thepax® administered to broilers in drinkable water may improve birds’ health and reduce abdominal fat without compromising carcass yield
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ISO Detection of CO<sup>+</sup> toward the protostar IRAS 16293-2422
In this letter we report the detection of eight high-N rotational transitions of CO+ towards a low mass protostar, IRAS 16293-2422. The source was observed with the Long Wavelength Spectrometer on board the Infrared Space Observatory. This is the first time that CO+ has been detected in a low luminosity source and the first time that high-N lines have been detected in any source. The detection of these lines was not predicted by models and consequently, their interpretation is a challenge. We discuss the possibility that the observed CO+ emission originates in the dense inner regions illuminated by the UV field created in the accretion shock (formed by infalling material), and conclude that this is an improbable explanation. We have also considered the possibility that a strong, dissociative J-shock at ~ 500 AU from the star is the origin of the CO+ emission. This model predicts CO+ column densities in rough agreement with the observations if the magnetic field is ~ 1 mG and the shock velocity is 100 km s-1
Trapped-ion quantum error-correcting protocols using only global operations
Quantum error-correcting codes are many-body entangled states that are
prepared and measured using complex sequences of entangling operations. Each
element of such an entangling sequence introduces noise to delicate quantum
information during the encoding or reading out of the code. It is important
therefore to find efficient entangling protocols to avoid the loss of
information. Here we propose an experiment that uses only global entangling
operations to encode an arbitrary logical qubit to either the five-qubit
repetition code or the five-qubit code, with a six-ion Coulomb crystal
architecture in a Penning trap. We show that the use of global operations
enables us to prepare and read out these codes using only six and ten global
entangling pulses, respectively. The proposed experiment also allows the
acquisition of syndrome information during readout. We provide a noise analysis
for the presented protocols, estimating that we can achieve a six-fold
improvement in coherence time with noise as high as on each
entangling operation.Comment: 7 pages, 4 figures, published version, comments are welcom
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Detection of CO<sup>+</sup> with ISO towards the protostar IRAS16293-242
We observed the low luminosity (and low mass) protostar IRAS16293-2422 with the Long Wavelength Spectrometer on board the Infrared Space Observatory. The observed line spectrum is very reach and shows transitions of several molecules and atoms. Here we report the detection of eight high-N rotational transitions of CO+. This is the first time that CO+ has been detected in a low luminosity source and the first time that high-N lines have been detected in any source. The detection of these lines was not predicted by models and consequently, their interpretation is a challenge. We discuss the possibility that the observed CO+ emission originates in the dense inner regions illuminated by the UV field created in the accretion shock (formed by infalling material), and conclude that this is an improbable explanation. We have also considered the possibility that a strong, dissociative J-shock at ~500 AU from the star is the origin of the CO+ emission. This model predicts CO+ column densities in rough agreement with the observations if the magnetic field is ~1 mG and the shock velocity is 100 km s-1
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