7,912 research outputs found
Discrete coherent states for higher Landau levels
We consider the quantum dynamics of a charged particle evolving under the
action of a constant homogeneous magnetic field, with emphasis on the discrete
subgroups of the Heisenberg group (in the Euclidean case) and of the SL(2, R)
group (in the Hyperbolic case). We investigate completeness properties of
discrete coherent states associated with higher order Euclidean and hyperbolic
Landau levels, partially extending classic results of Perelomov and of
Bargmann, Butera, Girardello and Klauder. In the Euclidean case, our results
follow from identifying the completeness problem with known results from the
theory of Gabor frames. The results for the hyperbolic setting follow by using
a combination of methods from coherent states, time-scale analysis and the
theory of Fuchsian groups and their associated automorphic forms.Comment: Revised for Annals of Physic
A study of high frequency nonlinear combustion instability in baffled annular liquid propellant rocket motors
Computer program contains mathematical model which provides relationship between engine gas dynamics and combustion processes. Mathematically simulated explosions initiate gas disturbances. Design methods for damping disturbances can be studied to prevent future engine shutdown or destruction
Experimental tests on the lifetime Asymmetry
The experimental test problem of the left-right polarization-dependent
lifetime asymmetry is discussed. It shows that the existing experiments cannot
demonstrate the lifetime asymmetry to be right or wrong after analyzing the
measurements on the neutron, the muon and the tau lifetime, as well as the
experiment. However, It is pointed out emphatically that the SLD and the
E158 experiments, the measurements of the left-right integrated cross section
asymmetry in boson production by collisions and by
electron-electron M{\o}ller scattering, can indirectly demonstrate the lifetime
asymmetry. In order to directly demonstrate the lifetime asymmetry, we propose
some possible experiments on the decays of polarized muons. The precise
measurement of the lifetime asymmetry could have important significance for
building a muon collider, also in cosmology and astrophysics. It would provide
a sensitive test of the standard model in particle physics and allow for
exploration of the possible interactions.Comment: 11 pages, 1 figur
Efficiency of a Brownian information machine
A Brownian information machine extracts work from a heat bath through a
feedback process that exploits the information acquired in a measurement. For
the paradigmatic case of a particle trapped in a harmonic potential, we
determine how power and efficiency for two variants of such a machine operating
cyclically depend on the cycle time and the precision of the positional
measurements. Controlling only the center of the trap leads to a machine that
has zero efficiency at maximum power whereas additional optimal control of the
stiffness of the trap leads to an efficiency bounded between 1/2, which holds
for maximum power, and 1 reached even for finite cycle time in the limit of
perfect measurements.Comment: 9 pages, 2 figure
Effective hadronic Lagrangian for charm mesons
An effective hadronic Lagrangian including the charm mesons is introduced to
study their interactions in hadronic matter. Using coupling constants that are
determined either empirically or by the SU(4) symmetry, we have evaluated the
absorption cross sections of and the scattering cross sections of
and by and mesons.Comment: 5 pages, 4 eps figures, presented at Strangeness 2000, Berkeley. Uses
iopart.cl
Four-jet angular distributions and color charge measurements: leading order versus next-to-leading order
We present the next-to-leading order perturbative QCD prediction to the
four-jet angular distributions used by experimental collaborations at LEP for
measuring the QCD color charge factors. We compare our results to ALEPH data
corrected to parton level. We perform a leading order ``measurement'' of the
QCD color factor ratios by fitting the leading order perturbative predictions
to the next-to-leading order result. Our result shows that in an experimental
analysis for measuring the color charge factors the use of the O()
QCD predictions instead of the O() results may shift the center of
the fit by a relative factor of 1+2\as in the direction.Comment: 14 pages, 10 tables, 5 figures, revtex, eps style
Universal features of the off-equilibrium fragmentation with the Gaussian dissipation
We investigate universal features of the off-equilibrium sequential and
conservative fragmentation processes with the dissipative effects which are
simulated by the Gaussian random inactivation process. The relation between the
fragment multiplicity scaling law and the fragment size distribution is studied
and a dependence of scaling exponents on the parameters of fragmentation and
inactivation rate functions is established.Comment: 10 pages, 2 figure
Energy Conservation Constraints on Multiplicity Correlations in QCD Jets
We compute analytically the effects of energy conservation on the
self-similar structure of parton correlations in QCD jets. The calculations are
performed both in the constant and running coupling cases. It is shown that the
corrections are phenomenologically sizeable. On a theoretical ground, energy
conservation constraints preserve the scaling properties of correlations in QCD
jets beyond the leading log approximation.Comment: 11 pages, latex, 5 figures, .tar.gz version avaliable on
ftp://www.inln.unice.fr
Determination of the QCD color factor ratio CA/CF from the scale dependence of multiplicity in three jet events
I examine the determination of the QCD color factor ratio CA/CF from the
scale evolution of particle multiplicity in e+e- three jet events. I fit an
analytic expression for the multiplicity in three jet events to event samples
generated with QCD multihadronic event generators. I demonstrate that a one
parameter fit of CA/CF yields the expected result CA/CF=2.25 in the limit of
asymptotically large energies if energy conservation is included in the
calculation. In contrast, a two parameter fit of CA/CF and a constant offset to
the gluon jet multiplicity, proposed in a recent study, does not yield
CA/CF=2.25 in this limit. I apply the one parameter fit method to recently
published data of the DELPHI experiment at LEP and determine the effective
value of CA/CF from this technique, at the finite energy of the Z0 boson, to be
1.74+-0.03+-0.10, where the first uncertainty is statistical and the second is
systematic.Comment: 20 pages including 6 figures Version 2 corrects typographical error
in equation (2
Microbial communities shifts in dark fermentative H2 production at mesophilic, thermophylic and hyperthermophylic conditions
Hydrogen is foreseen as a viable CO2-neutral alternative to fossil fuels for generation of energy.
Production of H2 from wastes/wastewaters is possible as this is one of the main products resulting from
anaerobic fermentation of organic compounds. If hydrogenotrophic methanogens are suppressed, H2-rich
biogas can be recovered from anaerobic reactors. In order to optimize and improve H2 production, it is
essential to get more insight into the composition and structure of the microbial communities involved in
the process. In this study microbial community shifts in expanded granular sludge blanket (EGSB)
reactors producing H2 at different temperatures and organic loading rates (OLR) were studied using PCRDGGE
fingerprinting analysis. The aim was to get more insight into the microbiology of dark
fermentative hydrogen production at mesophilic, thermophilic and hyperthermophilic temperatures. Three
EGSB reactors were inoculated with granular biomass previously treated with heat to suppress
methanogens. Reactors were operated at 37, 55 and 70 ÂșC with 5gCOD L-1of a mixture containing glucose
and L-arabinose (1:1); pH was kept at 5.5. OLR applied varied from 5 to 16. PCR amplification of the
16S rRNA gene and subsequent DGGE analysis of sludge samples collected from the reactors at different
operational times showed different profiling, mainly correlated with differences in temperature. Bacterial
diversity (measured as the number of bands) in sludge samples from reactors operating at 55 ÂșC and 70ÂșC
was remarkably lower than in sludges growing at 37ÂșC. No significant changes on DGGE profiles
diversity were observed with the increase of OLR over time
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