6,270 research outputs found
Transformation Optics with Photonic Band Gap Media
We introduce a class of optical media based on adiabatically modulated,
dielectric-only, and potentially extremely low-loss, photonic crystals. The
media we describe represent a generalization of the eikonal limit of
transformation optics (TO). The foundation of the concept is the possibility to
fit frequency isosurfaces in the k-space of photonic crystals with elliptic
surfaces, allowing them to mimic the dispersion relation of light in
anisotropic effective media. Photonic crystal cloaks and other TO devices
operating at visible wavelengths can be constructed from optically transparent
substances like glasses, whose attenuation coefficient can be as small as 10
dB/km, suggesting the TO design methodology can be applied to the development
of optical devices not limited by the losses inherent to metal-based, passive
metamaterials.Comment: 4 pages, 4 figure
Born-Infeld type Gravity
Generalizations of gravitational Born-Infeld type lagrangians are
investigated. Phenomenological constraints (reduction to Einstein-Hilbert
action for small curvature, spin two ghost freedom and absence of Coulomb like
Schwarschild singularity) select one effective lagrangian whose dynamics is
dictated by the tensors g_{\mu\nu} and R_{\mu\nu\rho\sigma}(not R_{\mu\nu} or
the scalar R).Comment: 7 pages, 3 figures, revte
Born-Infeld electrostatics in the complex plane
The complex method to obtain 2-dimensional Born-Infeld electrostatic
solutions is presented in a renewed form. The solutions are generated by a
holomorphic seed that makes contact with the Coulombian complex potential. The
procedure is exemplified by solving the Born-Infeld multipolar configurations.
Besides, it is shown that the attractive force between two equal but opposite
charges is lower than its Coulombian partner; it decreases up to vanish when
the charges approach each other below a distance ruled by the Born-Infeld
constant.Comment: 15 pages, 4 figure
Born-Regulated Gravity in Four Dimensions
Previous work involving Born-regulated gravity theories in two dimensions is
extended to four dimensions. The action we consider has two dimensionful
parameters. Black hole solutions are studied for typical values of these
parameters. For masses above a critical value determined in terms of these
parameters, the event horizon persists. For masses below this critical value,
the event horizon disappears, leaving a ``bare mass'', though of course no
singularity.Comment: LaTeX, 15 pages, 2 figure
Entanglement Generation by Qubit Scattering in Three Dimensions
A qubit (a spin-1/2 particle) prepared in the up state is scattered by local
spin-flipping potentials produced by the two target qubits (two fixed spins),
both prepared in the down state, to generate an entangled state in the latter
when the former is found in the down state after scattering. The scattering
process is analyzed in three dimensions, both to lowest order and in full order
in perturbation, with an appropriate renormalization for the latter. The
entanglement is evaluated in terms of the concurrence as a function of the
incident and scattering angles, the size of the incident wave packet, and the
detector resolution, to clarify the key elements for obtaining an entanglement
with high quality. The characteristics of the results are also discussed in the
context of (in)distinguishability of alternative paths for a quantum particle.Comment: 21 pages, 19 figures, the final versio
Comparison of imaging with sub-wavelength resolution in the canalization and resonant tunnelling regimes
We compare the properties of subwavelength imaging in the visible wavelength
range for metal-dielectric multilayers operating in the canalization and the
resonant tunnelling regimes. The analysis is based on the transfer matrix
method and time domain simulations. We show that Point Spread Functions for the
first two resonances in the canalization regime are approximately Gaussian in
shape. Material losses suppress transmission for higher resonances, regularise
the PSF but do not compromise the resolution. In the resonant tunnelling
regime, the MTF may dramatically vary in their phase dependence. Resulting PSF
may have a sub-wavelength thickness as well as may be broad with multiple
maxima and a rapid phase modulation. We show that the width of PSF may be
reduced by further propagation in free space, and we provide arguments to
explain this surprising observation.Comment: 17 pages,12 figure
Wigner quasi-probability distribution for the infinite square well: energy eigenstates and time-dependent wave packets
We calculate the Wigner quasi-probability distribution for position and
momentum, P_W^(n)(x,p), for the energy eigenstates of the standard infinite
well potential, using both x- and p-space stationary-state solutions, as well
as visualizing the results. We then evaluate the time-dependent Wigner
distribution, P_W(x,p;t), for Gaussian wave packet solutions of this system,
illustrating both the short-term semi-classical time dependence, as well as
longer-term revival and fractional revival behavior and the structure during
the collapsed state. This tool provides an excellent way of demonstrating the
patterns of highly correlated Schrodinger-cat-like `mini-packets' which appear
at fractional multiples of the exact revival time.Comment: 45 pages, 16 embedded, low-resolution .eps figures (higher
resolution, publication quality figures are available from the authors);
submitted to American Journal of Physic
Power dependence of pure spin current injection by quantum interference
We investigate the power dependence of pure spin current injection in GaAs
bulk and quantum-well samples by a quantum interference and control technique.
Spin separation is measured as a function of the relative strength of the two
transition pathways driven by two laser pulses. By keeping the relaxation time
of the current unchanged, we are able to relate the spin separation to the
injected average velocity. We find that the average velocity is determined by
the relative strength of the two transitions in the same way as in classical
interference. Based on this, we conclude that the density of injected pure spin
current increases monotonically with the excitation laser intensities. The
experimental results are consistent with theoretical calculations based on
Fermi's golden rule.Comment: 6 pages, 4 figure
On the physical origins of the negative index of refraction
The physical origins of negative refractive index are derived from a dilute
microscopic model, producing a result that is generalized to the dense
condensed phase limit. In particular, scattering from a thin sheet of electric
and magnetic dipoles driven above resonance is used to form a fundamental
description for negative refraction. Of practical significance, loss and
dispersion are implicit in the microscopic model. While naturally occurring
negative index materials are unavailable, ferromagnetic and ferroelectric
materials provide device design opportunities.Comment: 4 pages, 1 figur
In search of a working notion of lex sportiva
The emergence of a lex specialis regime and its interaction with the established, governing lex generalis in their overlapping spheres of application is always an intriguing legal relationship to explore. In this article, the focus will be on the development of legal principles and rules that have been/can be collectively described as lex sportiva. However, it is notable that those involved in the consideration, usage and application of this notion have not agreed as to the scope and delimitation of the concept. It is debated whether lex sportiva exists in the first place, its legal sources and its purpose. The risk is for the concept becoming redundant when not vilified as a hidden strategy to exclude non-sports-related law from the ambit of sport. Through an examination of the different propositions to the framework of the term, this article will shed light on the existence, utility and limits of the development of this conceptualisation
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