3,148 research outputs found
Quantum fluids in nanopores
We describe calculations of the properties of quantum fluids inside nanotubes
of various sizes. Very small radius () pores confine the gases to a line, so
that a one-dimensional (1D) approximation is applicable; the low temperature
behavior of 1D He is discussed. Somewhat larger pores permit the particles
to move off axis, resulting eventually in a transition to a cylindrical shell
phase--a thin film near the tube wall; we explored this behavior for H. At
even larger nm, both the shell phase and an axial phase are present.
Results showing strong binding of cylindrical liquids He and He are
discussed.Comment: 8 pages, 4 figures, uses ws-ijmpb, graphicx, xspace; minor revisions
from version published in Proc. 13th Intl. Conference on Recent Progress in
Many-Body Theories (QMBT13), Buenos Aires, 200
Realizability of metamaterials with prescribed electric permittivity and magnetic permeability tensors
We show that any pair of real symmetric tensors \BGve and \BGm can be
realized as the effective electric permittivity and effective magnetic
permeability of a metamaterial at a given fixed frequency. The construction
starts with two extremely low loss metamaterials, with arbitrarily small
microstructure, whose existence is ensured by the work of Bouchitt{\'e} and
Bourel and Bouchitt\'e and Schweizer, one having at the given frequency a
permittivity tensor with exactly one negative eigenvalue, and a positive
permeability tensor, and the other having a positive permittivity tensor, and a
permeability tensor having exactly one negative eigenvalue. To achieve the
desired effective properties these materials are laminated together in a
hierarchical multiple rank laminate structure, with widely separated length
scales, and varying directions of lamination, but with the largest length scale
still much shorter than the wavelengths and attenuation lengths in the
macroscopic effective medium.Comment: 12 pages, no figure
Spectral representation of the effective dielectric constant of graded composites
We generalize the Bergman-Milton spectral representation, originally derived
for a two-component composite, to extract the spectral density function for the
effective dielectric constant of a graded composite. This work has been
motivated by a recent study of the optical absorption spectrum of a graded
metallic film [Applied Physics Letters, 85, 94 (2004)] in which a broad
surface-plasmon absorption band has been shown to be responsible for enhanced
nonlinear optical response as well as an attractive figure of merit. It turns
out that, unlike in the case of homogeneous constituent components, the
characteristic function of a graded composite is a continuous function because
of the continuous variation of the dielectric function within the constituent
components. Analytic generalization to three dimensional graded composites is
discussed, and numerical calculations of multilayered composites are given as a
simple application.Comment: Physical Review E, submitted for publication
Twenty-first semiannual report to Congress, 1 January - 30 June 1969
Manned space flights, satellite observations, space sciences, and air traffic control - NASA report to Congress for 1 Jan. to 30 June 196
Electromagnetic field fluctuations near a dielectric-vacuum boundary and surface divergences in the ideal conductor limit
We consider the electric and magnetic field fluctuations in the vacuum state
in the region external to a half-space filled with a homogeneous
non-dissipative dielectric. We discuss an appropriate limit to an ideal metal
and concentrate our interest on the renormalized field fluctuations, or
equivalently to renormalized electric and magnetic energy densities, in the
proximity of the dielectric-vacuum interface. We show that surface divergences
of field fluctuations arise at the interface in an appropriate ideal conductor
limit, and that our limiting procedure allows to discuss in detail their
structure. Field fluctuations close to the surface can be investigated through
the retarded Casimir-Polder interaction with an appropriate polarizable body.Comment: 6 pages, 2 figure
Statistical-mechanical theory of the overall magnetic properties of mesocrystals
The mesocrystal showing both electrorheological and magnetorheological
effects is called electro-magnetorheological (EMR) solids. Prediction of the
overall magnetic properties of the EMR solids is a challenging task due to the
coexistence of the uniaxially anisotropic behavior and structural transition as
well as long-range interaction between the suspended particles. To consider the
uniaxial anisotropy effect, we present an anisotropic Kirkwood-Fr\"{o}hlich
equation for calculating the effective permeabilities by adopting an explicit
characteristic spheroid rather than a characteristic sphere used in the
derivation of the usual Kirkwood-Fr\"{o}hlich equation. Further, by applying an
Ewald-Kornfeld formulation we are able to investigate the effective
permeability by including the structural transition and long-range interaction
explicitly. Our theory can reduce to the usual Kirkwood-Fr\"{o}hlich equation
and Onsager equation naturally. To this end, the numerical simulation shows the
validity of monitoring the structure of EMR solids by detecting their effective
permeabilities.Comment: 14 pages, 1 figur
Dirac and Klein-Gordon particles in one-dimensional periodic potentials
We evaluate the dispersion relation for massless fermions, described by the
Dirac equation, and for zero-spin bosons, described by the Klein-Gordon
equation, moving in two dimensions and in the presence of a one-dimensional
periodic potential. For massless fermions the dispersion relation shows a zero
gap for carriers with zero momentum in the direction parallel to the barriers
in agreement with the well-known "Klein paradox". Numerical results for the
energy spectrum and the density of states are presented. Those for fermions are
appropriate to graphene in which carriers behave relativistically with the
"light speed" replaced by the Fermi velocity. In addition, we evaluate the
transmission through a finite number of barriers for fermions and zero-spin
bosons and relate it with that through a superlattice.Comment: 9 pages, 12 figure
Electromagnetic semitransparent -function plate: Casimir interaction energy between parallel infinitesimally thin plates
We derive boundary conditions for electromagnetic fields on a
-function plate. The optical properties of such a plate are shown to
necessarily be anisotropic in that they only depend on the transverse
properties of the plate. We unambiguously obtain the boundary conditions for a
perfectly conducting -function plate in the limit of infinite
dielectric response. We show that a material does not "optically vanish" in the
thin-plate limit. The thin-plate limit of a plasma slab of thickness with
plasma frequency reduces to a -function plate
for frequencies () satisfying . We show that the Casimir interaction energy between two parallel perfectly
conducting -function plates is the same as that for parallel perfectly
conducting slabs. Similarly, we show that the interaction energy between an
atom and a perfect electrically conducting -function plate is the usual
Casimir-Polder energy, which is verified by considering the thin-plate limit of
dielectric slabs. The "thick" and "thin" boundary conditions considered by
Bordag are found to be identical in the sense that they lead to the same
electromagnetic fields.Comment: 21 pages, 7 figures, references adde
Theory of Optical Transmission through Elliptical Nanohole Arrays
We present a theory which explains (in the quasistatic limit) the
experimentally observed [R. Gordon, {\it et al}, Phys. Rev. Lett. {\bf 92},
037401 (2004)] squared dependence of the depolarization ratio on the aspect
ratio of the holes, as well as other features of extraordinary light
transition. We calculated the effective dielectric tensor of a metal film
penetrated by elliptical cylindrical holes and found the extraordinarily light
transmission at special frequencies related to the surface plasmon resonances
of the composite film. We also propose to use the magnetic field for getting a
strong polarization effect, which depends on the ratio of the cyclotron to
plasmon frequencies.Comment: 4 pages, 4 figure
Investigation of a 0.6 Hub-tip Radius-ratio Transonic Turbine Designed for Secondary-flow Study IV : Rotor Loss Patterns as Determined by Hot-wire Anemometers with Rotor Operating in a Circumferentially Uniform Inlet Flow Field
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