6,193 research outputs found
Casimir Energies and Pressures for -function Potentials
The Casimir energies and pressures for a massless scalar field associated
with -function potentials in 1+1 and 3+1 dimensions are calculated. For
parallel plane surfaces, the results are finite, coincide with the pressures
associated with Dirichlet planes in the limit of strong coupling, and for weak
coupling do not possess a power-series expansion in 1+1 dimension. The relation
between Casimir energies and Casimir pressures is clarified,and the former are
shown to involve surface terms. The Casimir energy for a -function
spherical shell in 3+1 dimensions has an expression that reduces to the
familiar result for a Dirichlet shell in the strong-coupling limit. However,
the Casimir energy for finite coupling possesses a logarithmic divergence first
appearing in third order in the weak-coupling expansion, which seems
unremovable. The corresponding energies and pressures for a derivative of a
-function potential for the same spherical geometry generalizes the TM
contributions of electrodynamics. Cancellation of divergences can occur between
the TE (-function) and TM (derivative of -function) Casimir
energies. These results clarify recent discussions in the literature.Comment: 16 pages, 1 eps figure, uses REVTeX
Surface Divergences and Boundary Energies in the Casimir Effect
Although Casimir, or quantum vacuum, forces between distinct bodies, or
self-stresses of individual bodies, have been calculated by a variety of
different methods since 1948, they have always been plagued by divergences.
Some of these divergences are associated with the volume, and so may be more or
less unambiguously removed, while other divergences are associated with the
surface. The interpretation of these has been quite controversial. Particularly
mysterious is the contradiction between finite total self-energies and surface
divergences in the local energy density. In this paper we clarify the role of
surface divergences.Comment: 8 pages, 1 figure, submitted to proceedings of QFEXT0
Reply to the Comment on "The Lifshitz-Matsubara sum formula for the Casimir pressure between magnetic metallic mirrors"
We reply to the "Comment on 'The Lifshitz-Matsubara sum formula for the
Casimir pressure between magnetic metallic mirrors'" [arXiv:1604.06432]. We
believe the comment misrepresents our papers, and fails to provide a plausible
resolution to the conflict between theory and experiment.Comment: To appear in Phys. Rev.
Data visualization within urban models
Models of urban environments have many uses for town planning, pre-visualization of new building work and utility service planning. Many of these models are three-dimensional, and increasingly there is a move towards real-time presentation of such large models. In this paper we present an algorithm for generating consistent 3D models from a combination of data sources, including Ordnance Survey ground plans, aerial photography and laser height data. Although there have been several demonstrations of automatic generation of building models from 2D vector map data, in this paper we present a very robust solution that generates models that are suitable for real-time presentation. We then demonstrate a novel pollution visualization that uses these models
Green's Dyadic Approach of the Self-Stress on a Dielectric-Diamagnetic Cylinder with Non-Uniform Speed of Light
We present a Green's dyadic formulation to calculate the Casimir energy for a
dielectric-diamagnetic cylinder with the speed of light differing on the inside
and outside. Although the result is in general divergent, special cases are
meaningful. It is pointed out how the self-stress on a purely dielectric
cylinder vanishes through second order in the deviation of the permittivity
from its vacuum value, in agreement with the result calculated from the sum of
van der Waals forces.Comment: 8 pages, submitted to proceedings of QFEXT0
The Reality of Casimir Friction
For more than 35 years theorists have studied quantum or Casimir friction,
which occurs when two smooth bodies move transversely to each other,
experiencing a frictional dissipative force due to quantum electromagnetic
fluctuations, which break time-reversal symmetry. These forces are typically
very small, unless the bodies are nearly touching, and consequently such
effects have never been observed, although lateral Casimir forces have been
seen for corrugated surfaces. Partly because of the lack of contact with
phenomena, theoretical predictions for the frictional force between parallel
plates, or between a polarizable atom and a metallic plate, have varied widely.
Here we review the history of these calculations, show that theoretical
consensus is emerging, and offer some hope that it might be possible to
experimentally confirm this phenomenon of dissipative quantum electrodynamics.Comment: 12 pages, 2 figure
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