59,173 research outputs found
Scalar Casimir Energies for Separable Coordinate Systems: Application to Semi-transparent Planes in an Annulus
We derive a simplified general expression for the two-body scalar Casimir
energy in generalized separable coordinate systems. We apply this technique to
the case of radial semi-transparent planes in the annular region between two
concentric Dirichlet cylinders. This situation is explored both analytically
and numerically.Comment: 8 pages, 5 figures. Contribution to Proceedings of 9th Conference on
Quantum Field Theory Under the Influence of External Conditions, QFEXT0
Thin film dynamics on a vertically rotating disk partially immersed in a liquid bath
The axisymmetric flow of a thin liquid film is considered for the problem of
a vertically rotating disk that is partially immersed in a liquid bath. A model
for the fully three-dimensional free-boundary problem of the rotating disk,
that drags a thin film out of the bath is set up. From this, a
dimension-reduced extended lubrication approximation that includes the meniscus
region is derived. This problem constitutes a generalization of the classic
drag-out and drag-in problem to the case of axisymmetric flow. The resulting
nonlinear fourth-order partial differential equation for the film profile is
solved numerically using a finite element scheme. For a range of parameters
steady states are found and compared to asymptotic solutions. Patterns of the
film profile, as a function of immersion depth and angular velocity are
discussed.Comment: 31 pages, 19 figures accepted: Applied Mathematical Modellin
How does Casimir energy fall? III. Inertial forces on vacuum energy
We have recently demonstrated that Casimir energy due to parallel plates,
including its divergent parts, falls like conventional mass in a weak
gravitational field. The divergent parts were suitably interpreted as
renormalizing the bare masses of the plates. Here we corroborate our result
regarding the inertial nature of Casimir energy by calculating the centripetal
force on a Casimir apparatus rotating with constant angular speed. We show that
the centripetal force is independent of the orientation of the Casimir
apparatus in a frame whose origin is at the center of inertia of the apparatus.Comment: 8 pages, 2 figures, contribution to QFEXT07 proceeding
Trajectory-Based Dynamic Map Labeling
In this paper we introduce trajectory-based labeling, a new variant of
dynamic map labeling, where a movement trajectory for the map viewport is
given. We define a general labeling model and study the active range
maximization problem in this model. The problem is NP-complete and W[1]-hard.
In the restricted, yet practically relevant case that no more than k labels can
be active at any time, we give polynomial-time algorithms. For the general case
we present a practical ILP formulation with an experimental evaluation as well
as approximation algorithms.Comment: 19 pages, 7 figures, extended version of a paper to appear at ISAAC
201
Cosmic-ray induced background intercomparison with actively shielded HPGe detectors at underground locations
The main background above 3\,MeV for in-beam nuclear astrophysics studies
with -ray detectors is caused by cosmic-ray induced secondaries. The
two commonly used suppression methods, active and passive shielding, against
this kind of background were formerly considered only as alternatives in
nuclear astrophysics experiments. In this work the study of the effects of
active shielding against cosmic-ray induced events at a medium deep location is
performed. Background spectra were recorded with two actively shielded HPGe
detectors. The experiment was located at 148\,m below the surface of the Earth
in the Reiche Zeche mine in Freiberg, Germany. The results are compared to data
with the same detectors at the Earth's surface, and at depths of 45\,m and
1400\,m, respectively.Comment: Minor errors corrected; final versio
Phase relaxation of Faraday surface waves
Surface waves on a liquid air interface excited by a vertical vibration of a
fluid layer (Faraday waves) are employed to investigate the phase relaxation of
ideally ordered patterns. By means of a combined frequency-amplitude modulation
of the excitation signal a periodic expansion and dilatation of a square wave
pattern is generated, the dynamics of which is well described by a Debye
relaxator. By comparison with the results of a linear theory it is shown that
this practice allows a precise measurement of the phase diffusion constant.Comment: 5 figure
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
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