34,934 research outputs found
Anomalous Transport Processes in Anisotropically Expanding Quark-Gluon Plasmas
We derive an expression for the anomalous viscosity in an anisotropically
expanding quark-gluon-plasma, which arises from interactions of thermal partons
with dynamically generated color fields. The anomalous viscosity dominates over
the collisional viscosity for large velocity gradients or weak coupling. This
effect may provide an explanation for the apparent ``nearly perfect'' liquidity
of the matter produced in nuclear collisions at RHIC without the assumption
that it is a strongly coupled state.Comment: 31 pages, 1 figure, some typos in published version are correcte
To what extent would the poorest consumers nutritionally and socially benefit from a global food tax and subsidy reform ? A framed field experiment based on daily food intake
In this paper we propose a new method in experimental economics, designed to evaluate the effectiveness of public policy incentives aimed at altering consumer behaviors. We apply this method to wide-ranging policies on food prices, which use subsidies to increase the consumption of healthy products and taxes to reduce that of unhealthy ones. Our protocol allows for observation of an individual’s daily food consumption before and after the policy. We examine two separate policies: the one subsidizes fruit and vegetables, while the other one combines taxes and subsidies. We measure their nutritional and economic impacts on the choices of low-income French consumers, compared to a reference group. Both policies have a positive effect on the nutritional quality of food choices of the two groups but initial gaps widen, especially with the subsidies. In the low-income group this can be explained by an initially unfavorable pattern and by weaker price elasticities. The redistributive effects are therefore doubly regressive. Moreover, the individual price elasticities, that the experimental approach enables us to measure, show widely diverse behaviors. They are counter-effective for close to 40% of our sample of poor women.OBESITY;PUBLIC POLICY;SOCIAL INEQUALITIES;POVERTY;INCOME REDISTRIBUTION;REGRESSIVE TAX;INDIVIDUALIZED PRICE INDEX;NUTRITIONAL TAX SYSTEM;FOOD TAX
Comment on ``Intensity correlations and mesoscopic fluctuations of diffusing photons in cold atoms''
In a recent Letter (Phys. Rev. Lett. \textbf{98}, 083601 (2007),
arXiv:cond-mat/0610804), O. Assaf and E. Akkermans claim that the angular
correlations of the light intensity scattered by a cloud of cold atoms with
internal degeneracy (Zeeman sublevels) of the ground state overcome the usual
Rayleigh law. More precisely, they found that they become exponentially large
with the size of the sample. In what follows, we will explain why their results
are wrong and, in contrary, why the internal degeneracy leads to lower
intensity correlations.Comment: 1 page. Comment submitted to PR
Flame sprayed dielectric coatings improve heat dissipation in electronic packaging
Heat sinks in electronic packaging can be flame sprayed with dielectric coatings of alumina or beryllia and finished off with an organic sealer to provide high heat and electrical resistivity
``Plug and play'' systems for quantum cryptography
We present a time-multiplexed interferometer based on Faraday mirrors, and
apply it to quantum key distribution. The interfering pulses follow exactly the
same spatial path, ensuring very high stability and self balancing. Use of
Faraday mirrors compensates automatically any birefringence effects and
polarization dependent losses in the transmitting fiber. First experimental
results show a fringe visibility of 0.9984 for a 23km-long interferometer,
based on installed telecom fibers.Comment: LaTex, 6 pages, with 2 Postscript figures, Submitted to Applied
Physics Letter
Emission of Massive Scalar Fields by a Higher-Dimensional Rotating Black-Hole
We perform a comprehensive study of the emission of massive scalar fields by
a higher-dimensional, simply rotating black hole both in the bulk and on the
brane. We derive approximate, analytic results as well as exact numerical ones
for the absorption probability, and demonstrate that the two sets agree very
well in the low and intermediate-energy regime for scalar fields with mass
m_\Phi < 1 TeV in the bulk and m_\Phi < 0.5 TeV on the brane. The numerical
values of the absorption probability are then used to derive the Hawking
radiation power emission spectra in terms of the number of extra dimensions,
angular-momentum of the black hole and mass of the emitted field. We compute
the total emissivities in the bulk and on the brane, and demonstrate that,
although the brane channel remains the dominant one, the bulk-over-brane energy
ratio is considerably increased (up to 33%) when the mass of the emitted field
is taken into account.Comment: 28 pages, 18 figure
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