8,416 research outputs found
Tunneling mechanism of light transmission through metallic films
A mechanism of light transmission through metallic films is proposed,
assisted by tunnelling between resonating buried dielectric inclusions. This is
illustrated by arrays of Si spheres embedded in Ag. Strong transmission peaks
are observed near the Mie resonances of the spheres. The interaction among
various planes of spheres and interference effects between these resonances and
the surface plasmons of Ag lead to mixing and splitting of the resonances.
Transmission is proved to be limited only by absorption. For small spheres, the
effective dielectric constant can be tuned to values close to unity and a
method is proposed to turn the resulting materials invisible.Comment: 4 papges, 5 figure
The Analysis of Multijet Events Produced at High Energy Hadron Colliders
We define and discuss a set of (4N - 4) parameters that can be used to
analyse events in which N jets have been produced in high energy hadron-hadron
collisions. These multijet variables are the multijet mass and (4N - 5)
independent dimensionless parameters. To illustrate the use of the variables
QCD predictions are presented for events with up to five jets produced at the
Fermilab Tevatron Proton-Antiproton Collider. These QCD predictions are
compared with the predictions of a model in which multijet events uniformly
populate the N-body phase-space
The Rich Lack Close Neighbours: The Dependence of Blue-Straggler Fraction on Metallicity
Blue straggler stars (BSS) have been identified in star clusters and in field
populations in our own Milky Way galaxy and in its satellite galaxies. They
manifest as stars bluer and more luminous than the dominant old population, and
usually have a spatial distribution that follows the old population. Their
progenitors are likely to have been close binaries. We investigate trends of
the BSS population in dwarf spheroidal galaxies (dSph) and in the bulge of the
Milky Way and find an anti-correlation between the relative frequency of BSS
and the metallicity of the parent population. The rate of occurrence of BSS in
the metal-poor dwarf galaxies is approximately twice that found in the
solar-metallicity bulge population. This trend of decreasing relative
population of BSS with increasing metallicity mirrors that found for the
close-binary fraction in the field population of the Milky Way. We argue that
the dominant mode of BSS formation in low-density environments is likely to be
mass transfer in close-binary systems. It then follows that the similarity
between the trends for BSS in the dSph and field stars in our Galaxy supports
the proposal that the small-scale fragmentation during star formation is driven
by the same dominant physical process, despite the diversity in environments,
plausibly gravitational instability of proto-stellar discs.Comment: 11 pages, 3 figures, MNRAS in press (March 202
Relativistic predictions of spin observables for exclusive proton knockout reactions
Within the framework of the relativistic distorted wave impulse approximation
(DWIA), we investigate the sensitivity of complete sets of polarization
transfer observables for exclusive proton knockout from the 3s,
2d and 2d states in Pb, at an incident laboratory
kinetic energy of 202 MeV, and for coincident coplanar scattering angles
(, ), to different distorting optical potentials,
finite-range (FR) versus zero-range (ZR) approximations to the DWIA, as well as
medium-modified meson-nucleon coupling constants and meson masses. Results are
also compared to the nonrelativistic DWIA predictions based on the
Schr\"{o}dinger equation.Comment: Submitted for publication to Physicical Review C, 23 pages, 7 figure
Plasmon tunability in metallodielectric metamaterials
The dielectric properties of metamaterials consisting of periodically
arranged metallic nanoparticles of spherical shape are calculated by rigorously
solving Maxwell's equations. Effective dielectric functions are obtained by
comparing the reflectivity of planar surfaces limiting these materials with
Fresnel's formulas for equivalent homogeneous media, showing mixing and
splitting of individual-particle modes due to inter-particle interaction.
Detailed results for simple cubic and fcc crystals of aluminum spheres in
vacuum, silver spheres in vacuum, and silver spheres in a silicon matrix are
presented. The filling fraction of the metal f is shown to determine the
position of the plasmon modes of these metamaterials. Significant deviations
are observed with respect to Maxwell-Garnett effective medium theory for large
f, and multiple plasmons are predicted to exist in contrast to Maxwell-Garnett
theory.Comment: 6 pages, 4 figure
Recent Issues in Legal Education
Six issues in legal education, much discussed recently, were posed by the Editors of this Review to leading legal educators. These questions were and are frankly difficult and controversial, but their answers are important to our system of legal education and to our society. Capsule answers given by these distinguished legal educators are believed to be interesting and significant. Each is a personal rather than a representative opinion. Brief answers such as these, of course, are not expected to be, nor do they pretend to be, complete or profound. Their purpose is to indicate succinctly the approach of outstanding American opinion makers to difficult problems of legal education
Sequential Strong Measurements and Heat Vision
We study scenarios where a finite set of non-demolition von-Neumann
measurements are available. We note that, in some situations, repeated
application of such measurements allows estimating an infinite number of
parameters of the initial quantum state, and illustrate the point with a
physical example. We then move on to study how the system under observation is
perturbed after several rounds of projective measurements. While in the finite
dimensional case the effect of this perturbation always saturates, there are
some instances of infinite dimensional systems where such a perturbation is
accumulative, and the act of retrieving information about the system increases
its energy indefinitely (i.e., we have `Heat Vision'). We analyze this effect
and discuss a specific physical system with two dichotomic von-Neumann
measurements where Heat Vision is expected to show.Comment: See the Appendix for weird examples of heat visio
Origins of Mass
Newtonian mechanics posited mass as a primary quality of matter, incapable of
further elucidation. We now see Newtonian mass as an emergent property. Most of
the mass of standard matter, by far, arises dynamically, from back-reaction of
the color gluon fields of quantum chromodynamics (QCD). The equations for
massless particles support extra symmetries - specifically scale, chiral, and
gauge symmetries. The consistency of the standard model relies on a high degree
of underlying gauge and chiral symmetry, so the observed non-zero masses of
many elementary particles ( and bosons, quarks, and leptons) requires
spontaneous symmetry breaking. Superconductivity is a prototype for spontaneous
symmetry breaking and for mass-generation, since photons acquire mass inside
superconductors. A conceptually similar but more intricate form of
all-pervasive (i.e. cosmic) superconductivity, in the context of the
electroweak standard model, gives us a successful, economical account of
and boson masses. It also allows a phenomenologically successful, though
profligate, accommodation of quark and lepton masses. The new cosmic
superconductivity, when implemented in a straightforward, minimal way, suggests
the existence of a remarkable new particle, the so-called Higgs particle. The
mass of the Higgs particle itself is not explained in the theory, but appears
as a free parameter. Earlier results suggested, and recent observations at the
Large Hadron Collider (LHC) may indicate, the actual existence of the Higgs
particle, with mass GeV. In addition to consolidating our
understanding of the origin of mass, a Higgs particle with
GeV could provide an important clue to the future, as it is consistent with
expectations from supersymmetry.Comment: Invited review for the Central European Journal of Physics. This is
the supplement to my 2011 Solvay Conference talk promised there. It is
adapted from an invited talk given at the Atlanta APS meeting, April 2012. 33
pages, 6 figures. v2: Added update section bringing in the CERN discovery
announcemen
Algorithms for 3D rigidity analysis and a first order percolation transition
A fast computer algorithm, the pebble game, has been used successfully to
study rigidity percolation on 2D elastic networks, as well as on a special
class of 3D networks, the bond-bending networks. Application of the pebble game
approach to general 3D networks has been hindered by the fact that the
underlying mathematical theory is, strictly speaking, invalid in this case. We
construct an approximate pebble game algorithm for general 3D networks, as well
as a slower but exact algorithm, the relaxation algorithm, that we use for
testing the new pebble game. Based on the results of these tests and additional
considerations, we argue that in the particular case of randomly diluted
central-force networks on BCC and FCC lattices, the pebble game is essentially
exact. Using the pebble game, we observe an extremely sharp jump in the largest
rigid cluster size in bond-diluted central-force networks in 3D, with the
percolating cluster appearing and taking up most of the network after a single
bond addition. This strongly suggests a first order rigidity percolation
transition, which is in contrast to the second order transitions found
previously for the 2D central-force and 3D bond-bending networks. While a first
order rigidity transition has been observed for Bethe lattices and networks
with ``chemical order'', this is the first time it has been seen for a regular
randomly diluted network. In the case of site dilution, the transition is also
first order for BCC, but results for FCC suggest a second order transition.
Even in bond-diluted lattices, while the transition appears massively first
order in the order parameter (the percolating cluster size), it is continuous
in the elastic moduli. This, and the apparent non-universality, make this phase
transition highly unusual.Comment: 28 pages, 19 figure
On the use of surfaces of section in the N‐body ring problem
In the N‐body ring problem, we investigate the motion of a massless body interacting with N bodies of equal masses at the vertices of a regular polygon that rotates around a central mass. In this paper, we analyze the use of different surfaces of section in the numerical exploration of the escape in the N‐body ring problem in order to get some conclusions about the geometry of the basins of escape in the corresponding configuration spaces
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