1,546 research outputs found
Collective modes and correlations in one-component plasmas
The static and time-dependent potential and surface charge correlations in a
plasma with a boundary are computed for different shapes of the boundary. The
case of a spheroidal or spherical one-component plasma is studied in detail
because experimental results are available for such systems. Also, since there
is some knowlegde both experimental and theoretical about the electrostatic
collective modes of these plasmas, the time-dependent correlations are computed
using a method involving these modes.Comment: 20 pages, plain TeX, submitted to Phys. Rev.
Evolution of Ultracold, Neutral Plasmas
We present the first large-scale simulations of an ultracold, neutral plasma,
produced by photoionization of laser-cooled xenon atoms, from creation to
initial expansion, using classical molecular dynamics methods with open
boundary conditions. We reproduce many of the experimental findings such as the
trapping efficiency of electrons with increased ion number, a minimum electron
temperature achieved on approach to the photoionization threshold, and
recombination into Rydberg states of anomalously-low principal quantum number.
In addition, many of these effects establish themselves very early in the
plasma evolution ( ns) before present experimental observations begin.Comment: 4 pages, 3 figures, submitted to PR
Slow relaxation in the two dimensional electron plasma under the strong magnetic field
We study slow relaxation processes in the point vortex model for the
two-dimensional pure electron plasma under the strong magnetic field. By
numerical simulations, it is shown that, from an initial state, the system
undergoes the fast relaxation to a quasi-stationary state, and then goes
through the slow relaxation to reach a final state. From analysis of simulation
data, we find (i) the time scale of the slow relaxation increases linearly to
the number of electrons if it is measured by the unit of the bulk rotation
time, (ii) during the slow relaxation process, each electron undergoes an
superdiffusive motion, and (iii) the superdiffusive motion can be regarded as
the Levy flight, whose step size distribution is of the power law. The time
scale that each electron diffuses over the system size turns out to be much
shorter than that of the slow relaxation, which suggests that the correlation
among the superdiffusive trajectories is important in the slow relaxation
process.Comment: 11pages, 19 figures. Submitted to J. Phys. Soc. Jp
Glueball spectrum and the Pomeron in the Wilson loop approach
Using a nonperturbative method based on asymptotic behaviour of Wilson loops
we calculate masses of glueballs and corresponding Regge-trajectories. The only
input is string tension fixed by meson Regge slope, while perturbative
contributions to spin splittings are defined by standard alpha_s values. The
masses of lowest glueball states are in a perfect agreement with lattice
results. The leading glueball trajectory which is associated with Pomeron is
discussed in details and its mixing with f and f' trajectories is taken into
account.Comment: LaTeX2e, 49 pages, 2 figure
Decay constants of the heavy-light mesons from the field correlator method
Meson Green's functions and decay constants in different
channels are calculated using the Field Correlator Method. Both,
spectrum and , appear to be expressed only through universal
constants: the string tension , , and the pole quark masses.
For the -wave states the calculated masses agree with the experimental
numbers within MeV. For the and mesons the values of are equal to 210(10) and 260(10) MeV, respectively, and their ratio
=1.24(3) agrees with recent CLEO experiment. The values MeV are obtained for the , , and mesons
with the ratio =1.19(2) and =1.14(2). The decay constants
for the first radial excitations as well as the decay constants
in the vector channel are also calculated. The difference of
about 20% between and , and directly follows
from our analytical formulas.Comment: 37 pages, 10 tables, RevTeX
A consistent treatment for pion form factors in space-like and time-like regions
We write down some relevant matrix elements for the scattering and decay
processes of the pion by considering a quark-meson vertex function. The pion
charge and transition form factors , , and
are extracted from these matrix elements using a relativistic
quark model on the light-front. We found that, the form factors and
in the space-like region agree well with experiment.
Furthermore, the branching ratios of all observed decay modes of the neutral
pion, that are related to the form factors and
in the time-like region, are all consistent with the data as
well. Additionally, in the time-like region, which deals with the
nonvalence contribution, is also discussed.Comment: 24 pages, 6 figures, to appear in Phys. Rev.
Baryon magnetic moments in the QCD string approach
Magnetic moments of baryons composed of light and strange quarks are computed
for the first time through the only parameter of the model -- string tension
. Resulting theoretical values differ from the experimental ones
typically by about
10%.Comment: LaTeX, 13 pages; misprints are correcte
Dislocation-Mediated Melting: The One-Component Plasma Limit
The melting parameter of a classical one-component plasma is
estimated using a relation between melting temperature, density, shear modulus,
and crystal coordination number that follows from our model of
dislocation-mediated melting. We obtain in good agreement
with the results of numerous Monte-Carlo calculations.Comment: 8 pages, LaTe
Melting of the classical bilayer Wigner crystal: influence of the lattice symmetry
The melting transition of the five different lattices of a bilayer crystal is
studied using the Monte-Carlo technique. We found the surprising result that
the square lattice has a substantial larger melting temperature as compared to
the other lattice structures, which is a consequence of the specific topology
of the temperature induced defects. A new melting criterion is formulated which
we show to be universal for bilayers as well as for single layer crystals.Comment: 4 pages, 5 figures (postscript files). Accepted in Physical Review
Letter
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