931 research outputs found
A van der Waals free energy in electrolytes revisited
A system of three electrolytes separated by two parallel planes is
considered. Each region is described by a dielectric constant and a Coulomb
fluid in the Debye-H\"uckel regime. In their book Dispersion Forces, Mahanty
and Ninham have given the van der Waals free energy of this system. We rederive
this free energy by a different method, using linear response theory and the
electrostatic Maxwell stress tensor for obtaining the dispersion force.Comment: 7 pages. PACS numbers updated. References update
Indigenous Representation in Cinema
Indigenous people are underrepresented offscreen on film-sets, and misrepresented onscreen. This has always been true in cinema and progress towards proper representation has been incredibly slow.
This has effects both on Indigenous people, and how the rest of society views them. It limits career opportunities for Indigenous filmmakers, restricts Indigenous role models on film, and reinforces cultural misunderstandings in society.https://ir.lib.uwo.ca/headandheartprogram_2019/1007/thumbnail.jp
Resonance Interaction Induced by Metal Surfaces Catalyses Atom Pair Breakage
We present the theory for retarded resonance interaction between two
identical atoms at arbitrary positions near a metal surface. The dipole-dipole
resonance interaction force that binds isotropically excited atom pairs
together in free space may turn repulsive close to an ideal (totally
reflecting) metal surface. On the other hand, close to an infinitely permeable
surface it may turn more attractive. We illustrate numerically how the
dipole-dipole resonance interaction between two oxygen atoms near a metal
surface may provide a repulsive energy of the same order of magnitude as the
ground-state binding energy of an oxygen molecule. As a complement we also
present results from density-functional theory.Comment: 5 pages, 5 figure
Atomic resonance interaction in dielectric media
The retarded resonance interaction in dielectric media between a ground state atom and an excited atom were investigated. The whole system was represented by a superposition of states:symmetric and antisymmetric with respect to interchange of atoms. While the antisymmetric state can be long lived, the asymmetric state is likely to decay into two ground state atoms. The retarded limit large deviations were demonstrated
Thermal radiation and near-field energy density of thin metallic films
We study the properties of thermal radiation emitted by a thin dielectric
slab, employing the framework of macroscopic fluctuational electrodynamics.
Particular emphasis is given to the analytical construction of the required
dyadic Green's functions. Based on these, general expressions are derived for
both the system's Poynting vector, describing the intensity of propagating
radiation, and its energy density, containing contributions from
non-propagating modes which dominate the near-field regime. An extensive
discussion is then given for thin metal films. It is shown that the radiative
intensity is maximized for a certain film thickness, due to Fabry-Perot-like
multiple reflections inside the film. The dependence of the near-field energy
density on the distance from the film's surface is governed by an interplay of
several length scales, and characterized by different exponents in different
regimes. In particular, this energy density remains finite even for arbitrarily
thin films. This unexpected feature is associated with the film's low-frequency
surface plasmon polariton. Our results also serve as reference for current
near-field experiments which search for deviations from the macroscopic
approach
Retardation turns the van der Waals attraction into Casimir repulsion already at 3 nm
Casimir forces between surfaces immersed in bromobenzene have recently been
measured by Munday et al. Attractive Casimir forces were found between gold
surfaces. The forces were repulsive between gold and silica surfaces. We show
the repulsion is due to retardation effects. The van der Waals interaction is
attractive at all separations. The retardation driven repulsion sets in already
at around 3 nm. To our knowledge retardation effects have never been found at
such a small distance before. Retardation effects are usually associated with
large distances
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