41,882 research outputs found
Macroscopic approximation to relativistic kinetic theory from a nonlinear closure
We use a macroscopic description of a system of relativistic particles based
on adding a nonequilibrium tensor to the usual hydrodynamic variables. The
nonequilibrium tensor is linked to relativistic kinetic theory through a
nonlinear closure suggested by the Entropy Production Principle; the evolution
equation is obtained by the method of moments, and together with
energy-momentum conservation closes the system. Transport coefficients are
chosen to reproduce second order fluid dynamics if gradients are small. We
compare the resulting formalism to exact solutions of Boltzmann's equation in
0+1 dimensions and show that it tracks kinetic theory better than second order
fluid dynamics.Comment: v2: 6 two-column pages, 2 figures. Corrected typos and a numerical
error, and added reference
A hydrodynamic approach to QGP instabilities
We show that the usual linear analysis of QGP Weibel instabilities based on
the Maxwell-Boltzmann equation may be reproduced in a purely hydrodynamic
model. The latter is derived by the Entropy Production Variational Method from
a transport equation including collisions, and can describe highly
nonequilibrium flow. We find that, as expected, collisions slow down the growth
of Weibel instabilities. Finally, we discuss the strong momentum anisotropy
limit.Comment: 11 pages, no figures. v2: minor changes, added references. Accepted
in Phys. Rev.
On the nature of the Lambda(1405) as a superposition of two states
We use recent data on the reaction with the
mass distribution of forming the with a peak
at 1420 MeV and a relatively narrow width of MeV, together with
those of the reaction to show that there are two
states instead of one as so far assumed.Comment: Contribution to the PANIC05 Conference, Santa Fe, October 200
Triangle singularities in and
We study the appearance of structures in the decay of the into and final states by forming
invariant mass distributions of and pairs,
respectively. The structure in the distribution is associated to the
kinematical triangle singularity that appears when the () decay process is followed by the decay
of the into and the subsequent rescattering of the () pair forming the ()
resonance. We find this type of non-resonant peaks at 2850 MeV in the invariant
mass of pairs from decays and
around 3000 MeV in the invariant mass of pairs from decays. By employing the measured branching ratios of
the and decays, we
predict the branching ratios for the processes into and , in the vicinity of the
triangle singularity peak, to be about and ,
respectively. The observation of this reaction would also give extra support to
the molecular picture of the and .Comment: 18 pages, 15 figures, accepted version for publication in Eur. Phys.
J.
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