25,521 research outputs found
An Accelerated Multiboson Algorithm for Coulomb Gases with Dynamical Dielectric Effects
A recent reformulation [1] of the problem of Coulomb gases in the presence of
a dynamical dielectric medium showed that finite temperature simulations of
such systems can be accomplished on the basis of completely local Hamiltonians
on a spatial lattice by including additional bosonic fields. For large systems,
the Monte Carlo algorithm proposed in Ref. [1] becomes inefficient due to a low
acceptance rate for particle moves in a fixed background multiboson field. We
show here how this problem can be circumvented by use of a coupled
particle-multiboson update procedure that improves acceptance rates on large
lattices by orders of magnitude. The method is tested on a one-component plasma
with neutral dielectric particles for a variety of system sizes.Comment: 13 pages, 2 figures, fixed typos, added reference
Local Simulation Algorithms for Coulomb Gases with Dynamical Dielectric Effects
We discuss the application of the local lattice technique of Maggs and
Rossetto to problems that involve the motion of objects with different
dielectric constants than the background. In these systems the simulation
method produces a spurious interaction force which causes the particles to move
in an unphysical manner. We show that this term can be removed using a variant
of a method known from high-energy physics simulations, the multiboson method,
and demonstrate the effectiveness of this corrective method on a system of
neutral particles. We then apply our method to a one-component plasma to show
the effect of the spurious interaction term on a charged system.Comment: 13 pages, 4 figure
On gigahertz spectral turnovers in pulsars
Pulsars are known to emit non-thermal radio emission that is generally a
power-law function of frequency. In some cases, a turnover is seen at
frequencies around 100~MHz. Kijak et al. have reported the presence of a new
class of ''Gigahertz Peaked Spectrum'' (GPS) pulsars that show spectral
turnovers at frequencies around 1 GHz. We apply a model based on free-free
thermal absorption to explain these turnovers in terms of surrounding material
such as the dense environments found in HII regions, Pulsar Wind Nebulae
(PWNe), or in cold, partially ionized molecular clouds. We show that the
turnover frequency depends on the electron temperature of the environment close
to the pulsar, as well as the emission measure along the line of sight. We
fitted this model to the radio fluxes of known GPS pulsars and show that it can
replicate the GHz turnover. From the thermal absorption model, we demonstrate
that normal pulsars would exhibit a GPS-like behaviour if they were in a dense
environment. We discuss the application of this model in the context of
determining the population of neutron stars within the central parsec of the
Galaxy. We show that a non-negligible fraction of this population might exhibit
high-frequency spectral turnovers, which has implications on the detectability
of these sources in the Galactic centre.Comment: 7 pages, 3 figures, Accepted for publication in MNRA
RURAL ECONOMIC DEVELOPMENT: NEW OPPORTUNITIES AND CHALLENGES FOR COMMERCIAL BANKERS
The report discusses commercial banks' role in supporting economic development in rural America. It details demographic and economic trends in rural America. It discusses a number of economic development programs available to commercial bankers and to private sector/public sector partnerships. Finally, the report proposes a set of new tools for commercial bankers to further strengthen their participation in rural community economic development. Note: Figures are not included in the machine readable copy--contact the authors for more information.demographic trends, economic trends, rural America, role of commercial banks, economic development programs, new tools for bankers, Community/Rural/Urban Development, Financial Economics,
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