1,492 research outputs found
W(infty)-Covariance of the Weyl-Wigner-Groenewold-Moyal Quantization
The differential structure of operator bases used in various forms of the
Weyl-Wigner-Groenewold-Moyal (WWGM) quantization is analyzed and a
derivative-based approach, alternative to the conventional integral-based one
is developed. Thus the fundamental quantum relations follow in a simpler and
unified manner. An explicit formula for the ordered products of the
Heisenberg-Weyl algebra is obtained. The W(infty) -covariance of the
WWGM-quantization in its most general form is established. It is shown that the
group action of W(infty) that is realized in the classical phase space induces
on bases operators in the corresponding Hilbert space a similarity
transformation generated by the corresponding quantum W(infty) which provides a
projective representation of the former . Explicit expressions for
the algebra generators in the classical phase space and in the Hilbert space
are given. It is made manifest that this W(infty)-covariance of the
WWGM-quantization is a genuine property of the operator bases.Comment: 14 pages, Latex file. No figures. To apear in J. Math. Phy
Relationship Among Waist Girth, Body Mass Index, Total Cholesterol In College-Aged Males
Please refer to the pdf version of the abstract located adjacent to the title
Initial State: Theory Status
I present a brief discussion of the different approaches to the study initial
state effects in heavy ion collisions in view of the recent results from Pb+Pb
and p+p collisions at the LHC.Comment: 8 pages, 6 figures. Contribution to the proceedings of the XXII
International Conference on Ultrarelativistic Nucleus-Nucleus Collisions,
QM2011. Annecy, France, 22-28 May 201
The Moyal-Lie Theory of Phase Space Quantum Mechanics
A Lie algebraic approach to the unitary transformations in Weyl quantization
is discussed. This approach, being formally equivalent to the
-quantization, is an extension of the classical Poisson-Lie formalism
which can be used as an efficient tool in the quantum phase space
transformation theory.Comment: 15 pages, no figures, to appear in J. Phys. A (2001
Projected pH reductions by 2100 might put deep North Atlantic biodiversity at risk
This study aims to evaluate the potential for impacts of ocean acidification on North Atlantic deep-sea ecosystems in response to IPCC AR5 Representative Concentration Pathways (RCPs). Deep-sea biota is likely highly vulnerable to changes in seawater chemistry and sensitive to moderate excursions in pH. Here we show, from seven fully coupled Earth system models, that for three out of four RCPs over 17% of the seafloor area below 500 m depth in the North Atlantic sector will experience pH reductions exceeding ?0.2 units by 2100. Increased stratification in response to climate change partially alleviates the impact of ocean acidification on deep benthic environments. We report on major pH reductions over the deep North Atlantic seafloor (depth >500 m) and at important deep-sea features, such as seamounts and canyons. By 2100, and under the high CO2 scenario RCP8.5, pH reductions exceeding ?0.2 (?0.3) units are projected in close to 23% (~15%) of North Atlantic deep-sea canyons and ~8% (3%) of seamounts – including seamounts proposed as sites of marine protected areas. The spatial pattern of impacts reflects the depth of the pH perturbation and does not scale linearly with atmospheric CO2 concentration. Impacts may cause negative changes of the same magnitude or exceeding the current target of 10% of preservation of marine biomes set by the convention on biological diversity, implying that ocean acidification may offset benefits from conservation/management strategies relying on the regulation of resource exploitation
Hard diffraction in hadron--hadron interactions and in photoproduction
Hard single diffractive processes are studied within the framework of the
triple--Pomeron approximation. Using a Pomeron structure function motivated by
Regge--theory we obtain parton distribution functions which do not obey
momentum sum rule. Based on Regge-- factorization cross sections for hard
diffraction are calculated. Furthermore, the model is applied to hard
diffractive particle production in photoproduction and in
interactions.Comment: 13 pages, Latex, 13 uuencoded figure
Cosmic-ray Monte Carlo predictions for forward particle production in p-p, p-Pb, and Pb-Pb collisions at the LHC
We present and compare the predictions of various cosmic-ray Monte Carlo
models for the energy (dE/deta) and particle (dN/deta) flows in p-p, p-Pb and
Pb-Pb collisions at sqrt(s) = 14, 8.8, and 5.5 TeV respectively, in the range
covered by forward LHC detectors like CASTOR or TOTEM (5.2<|eta|<6.6) and ZDC
or LHCf (|eta|>8.1 for neutrals).Comment: 5 pages, 5 figs. Poster proceedings Quark-Matter'08, Jaipur. To
appear in Indian J. of Phy
Pulse Profiles, Accretion Column Dips and a Flare in GX 1+4 During a Faint State
The Rossi X-ray Timing Explorer (RXTE) spacecraft observed the X-ray pulsar
GX 1+4 for a period of 34 hours on July 19/20 1996. The source faded from an
intensity of ~20 mCrab to a minimum of <~0.7 mCrab and then partially recovered
towards the end of the observation. This extended minimum lasted ~40,000
seconds. Phase folded light curves at a barycentric rotation period of
124.36568 +/- 0.00020 seconds show that near the center of the extended minimum
the source stopped pulsing in the traditional sense but retained a weak dip
feature at the rotation period. Away from the extended minimum the dips are
progressively narrower at higher energies and may be interpreted as
obscurations or eclipses of the hot spot by the accretion column. The pulse
profile changed from leading-edge bright before the extended minimum to
trailing-edge bright after it. Data from the Burst and Transient Source
Experiment (BATSE) show that a torque reversal occurred <10 days after our
observation. Our data indicate that the observed rotation departs from a
constant period with a Pdot/P value of ~-1.5% per year at a 4.5 sigma
significance. We infer that we may have serendipitously obtained data, with
high sensitivity and temporal resolution about the time of an accretion disk
spin reversal. We also observed a rapid flare which had some precursor
activity, close to the center of the extended minimum.Comment: 19 pages, 6 figures, accepted for publication in Astrophysical
Journal (tentatively scheduled for vol. 529 #1, 20 Jan 2000
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