5,614 research outputs found
Self-Interacting Electromagnetic Fields and a Classical Discussion on the Stability of the Electric Charge
The present work proposes a discussion on the self-energy of charged
particles in the framework of nonlinear electrodynamics. We seek magnet- ically
stable solutions generated by purely electric charges whose electric and
magnetic fields are computed as solutions to the Born-Infeld equa- tions. The
approach yields rich internal structures that can be described in terms of the
physical fields with explicit analytic solutions. This suggests that the
anomalous field probably originates from a magnetic excitation in the vacuum
due to the presence of the very intense electric field. In addition, the
magnetic contribution has been found to exert a negative pressure on the
charge. This, in turn, balances the electric repulsion, in such a way that the
self-interaction of the field appears as a simple and natural classical
mechanism that is able to account for the stability of the electron charge.Comment: 8 pages, 1 figur
Evaluation of Born and local effective charges in unoriented materials from vibrational spectra
We present an application of the Lorentz model in which fits to vibrational
spectra or a Kramers Kronig analysis are employed along with several useful
formalisms to quantify microscopic charge in unoriented (powdered) materials.
The conditions under which these techniques can be employed are discussed, and
we analyze the vibrational response of a layered transition metal
dichalcogenide and its nanoscale analog to illustrate the utility of this
approach.Comment: 9 pages, 1 figur
New Perspective on the Optical Theorem of Classical Electrodynamics
A general proof of the optical theorem (also known as the optical
cross-section theorem) is presented that reveals the intimate connection
between the forward scattering amplitude and the absorption-plus-scattering of
the incident wave within the scatterer. The oscillating electric charges and
currents as well as the electric and magnetic dipoles of the scatterer, driven
by an incident plane-wave, extract energy from the incident beam at a certain
rate. The same oscillators radiate electro-magnetic energy into the far field,
thus giving rise to well-defined scattering amplitudes along various
directions. The essence of the proof presented here is that the extinction
cross-section of an object can be related to its forward scattering amplitude
using the induced oscillations within the object but without an actual
knowledge of the mathematical form assumed by these oscillations.Comment: 7 pages, 1 figure, 12 reference
The Fertility Problem Inventory and Infertility-Related Stress: A Case Study
More than seven million people of childbearing age in the United States experience infertility. Oftentimes, for women, the experience of infertility is stressful. The Fertility Problem Inventory (FPI) has been used to quantitatively measure women’s experience of infertility-related stress. However, the construct of infertility-related stress is poorly described in existing literature. The purpose of this case study was to understand how women experience the FPI as a measure of infertility-related stress. To address this issue, women who were undergoing infertility treatment completed the FPI and participated in unstructured interviews. Archival documents were also retrieved to corroborate findings and satisfy saturation. Results indicated that the FPI is lacking in structure and organization to describe women’s experiences of infertility-related stress. Specifically, women described feeling infertility having an influence upon their identity and their coping
Duality Between Spatial and Angular Shift in Optical Reflection
We report a unified representation of the spatial and angular Goos-Hanchen
and Imbert-Fedorov shifts that occur when a light beam reflects from a plane
interface. We thus reveal the dual nature of spatial and angular shifts in
optical beam reflection. In the Goos-Hanchen case we show theoretically and
experimentally that this unification naturally arises in the context of
reflection from a lossy surface (e.g., a metal).Comment: 4 pages, 3 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
The temperature dependence of the isothermal bulk modulus at 1 bar pressure
It is well established that the product of the volume coefficient of thermal
expansion and the bulk modulus is nearly constant at temperatures higher than
the Debye temperature. Using this approximation allows predicting the values of
the bulk modulus. The derived analytical solution for the temperature
dependence of the isothermal bulk modulus has been applied to ten substances.
The good correlations to the experiments indicate that the expression may be
useful for substances for which bulk modulus data are lacking
Surface spontaneous parametric down-conversion
Surface spontaneous parametric down-conversion is predicted as a consequence
of continuity requirements for electric- and magnetic-field amplitudes at a
discontinuity of chi2 nonlinearity. A generalization of the usual two-photon
spectral amplitude is suggested to describe this effect. Examples of nonlinear
layered structures and periodically-poled nonlinear crystals show that surface
contributions to spontaneous down-conversion can be important.Comment: 4 pages, 3 figure
Nonaffine Correlations in Random Elastic Media
Materials characterized by spatially homogeneous elastic moduli undergo
affine distortions when subjected to external stress at their boundaries, i.e.,
their displacements \uv (\xv) from a uniform reference state grow linearly
with position \xv, and their strains are spatially constant. Many materials,
including all macroscopically isotropic amorphous ones, have elastic moduli
that vary randomly with position, and they necessarily undergo nonaffine
distortions in response to external stress. We study general aspects of
nonaffine response and correlation using analytic calculations and numerical
simulations. We define nonaffine displacements \uv' (\xv) as the difference
between \uv (\xv) and affine displacements, and we investigate the
nonaffinity correlation function
and related functions. We introduce four model random systems with random
elastic moduli induced by locally random spring constants, by random
coordination number, by random stress, or by any combination of these. We show
analytically and numerically that scales as A |\xv|^{-(d-2)}
where the amplitude is proportional to the variance of local elastic moduli
regardless of the origin of their randomness. We show that the driving force
for nonaffine displacements is a spatial derivative of the random elastic
constant tensor times the constant affine strain. Random stress by itself does
not drive nonaffine response, though the randomness in elastic moduli it may
generate does. We study models with both short and long-range correlations in
random elastic moduli.Comment: 22 Pages, 18 figures, RevTeX
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