4,926 research outputs found
Nonperturbative calculation of Born-Infeld effects on the Schroedinger spectrum of the hydrogen atom
We present the first nonperturbative numerical calculations of the
nonrelativistic hydrogen spectrum as predicted by first-quantized
electrodynamics with nonlinear Maxwell-Born-Infeld field equations. We also
show rigorous upper and lower bounds on the ground state.
When judged against empirical data our results significantly restrict the
range of viable values of the new electromagnetic constant which is introduced
by the Born-Infeld theory.
We assess Born's own proposal for the value of his constant.Comment: 4p., 2 figs, 1 table; submitted for publicatio
Adiabatic and Non-Adiabatic Contributions to the Free Energy from the Electron-Phonon Interaction for Na, K, Al, and Pb
We calculate the adiabatic contributions to the free energy due to the
electron--phonon interaction at intermediate temperatures, for the elemental metals Na, K, Al, and Pb. Using our
previously published results for the nonadiabatic contributions we show that
the adiabatic contribution, which is proportional to at low
temperatures and goes as at high temperatures, dominates the
nonadiabatic contribution for temperatures above a cross--over temperature,
, which is between 0.5 and 0.8 , where is the melting
temperature of the metal. The nonadiabatic contribution falls as for
temperatures roughly above the average phonon frequency.Comment: Updated versio
Genuine Dyons in Born-Infeld Electrodynamics
Study of magnetic monopoles in the original version of Born-Infeld (BI)
electrodynamics is performed. It then is realized that interesting new physics
emerge and they include exotic behavior of radial electric monopole field such
as its regularity as and its changing behavior with the absence or
presence of the radial magnetic monopole field. This last point has been
interpreted as the manifestation of the existence of point-like dyons in
abelian BI theory. Two pieces of clear evidences in favor of this dyon
interpretation are provided. It is also demonstrated that despite these unique
features having no analogues in standard Maxwell theory, the cherished Dirac
quantisation condition remains unchanged. Lastly, comments are given concerning
that dyons found here in the original version of BI electrodynamics should be
distinguished from the ones with the same name or BIons being studied in the
recent literature on D-brane physics.Comment: 19 pages, Revtex, references added, no other change
A technique for optimal temperature estimation for modeling sunrise/sunset thermal snap disturbance torque
A predictive temperature estimation technique which can be used to drive a model of the Sunrise/Sunset thermal 'snap' disturbance torque experienced by low Earth orbiting spacecraft is described. The twice per orbit impulsive disturbance torque is attributed to vehicle passage in and out of the Earth's shadow cone (umbra), during which large flexible appendages undergo rapidly changing thermal conditions. Flexible members, in particular solar arrays, experience rapid cooling during umbra entrance (Sunset) and rapid heating during exit (Sunrise). The thermal 'snap' phenomena has been observed during normal on-orbit operations of both the LANDSAT-4 satellite and the Communications Technology Satellite (CTS). Thermal 'snap' has also been predicted to be a dominant source of error for the TOPEX satellite. The fundamental equations used to model the Sunrise/Sunset thermal 'snap' disturbance torque for a typical solar array like structure will be described. For this derivation the array is assumed to be a thin, cantilevered beam. The time varying thermal gradient is shown to be the driving force behind predicting the thermal 'snap' disturbance torque and therefore motivates the need for accurate estimates of temperature. The development of a technique to optimally estimate appendage surface temperature is highlighted. The objective analysis method used is structured on the Gauss-Markov Theorem and provides an optimal temperature estimate at a prescribed location given data from a distributed thermal sensor network. The optimally estimated surface temperatures could then be used to compute the thermal gradient across the body. The estimation technique is demonstrated using a typical satellite solar array
Single and double slit scattering of wave packets
The scattering of wave packets from a single slit and a double slit with the
Schr\"odinger equation, is studied numerically and theoretically.
The phenomenon of diffraction of wave packets in space and time in the
backward region, previously found for barriers and wells, is encountered here
also.
A new phenomenon of forward diffraction that occurs only for packets thiner
than the slit, or slits, is calculated numerically as well as, in a theoretical
approximation to the problem. This diffraction occurs at the opposite end of
the usual diffraction phenomena with monochromatic waves.Comment: Latex format, 35 pages, 15 eps (some colored) figure
Polarization and angular distribution of the radiation emitted in laser-assisted recombination
The effect of an intense external linear polarized radiation field on the
angular distributions and polarization states of the photons emitted during the
radiative recombination is investigated. It is predicted, on symmetry grounds,
and corroborated by numerical calculations of approximate recombination rates,
that emission of elliptically polarized photons occurs when the momentum of the
electron beam is not aligned to the direction of the oscillating field.
Moreover, strong modifications to the angular distributions of the emitted
photons are induced by the external radiation field.Comment: 5 pages, 3 figure
Seasat data utilization project
During the three months of orbital operations, the satellite returned data from the world's oceans. Dozens of tropical storms, hurricanes and typhoons were observed, and two planned major intensive surface truth experiments were conducted. The utility of the Seasat-A microwave sensors as oceanographic tools was determined. Sensor and geophysical evaluations are discussed, including surface observations, and evaluation summaries of an altimeter, a scatterometer, a scanning multichannel microwave radiometer, a synthetic aperture radar, and a visible and infrared radiometer
Perfect imaging with positive refraction in three dimensions
Maxwell's fish eye has been known to be a perfect lens within the validity
range of ray optics since 1854. Solving Maxwell's equations we show that the
fish-eye lens in three dimensions has unlimited resolution for electromagnetic
waves
An analytic model of rotationally inelastic collisions of polar molecules in electric fields
We present an analytic model of thermal state-to-state rotationally inelastic
collisions of polar molecules in electric fields. The model is based on the
Fraunhofer scattering of matter waves and requires Legendre moments
characterizing the "shape" of the target in the body-fixed frame as its input.
The electric field orients the target in the space-fixed frame and thereby
effects a striking alteration of the dynamical observables: both the phase and
amplitude of the oscillations in the partial differential cross sections
undergo characteristic field-dependent changes that transgress into the partial
integral cross sections. As the cross sections can be evaluated for a field
applied parallel or perpendicular to the relative velocity, the model also
offers predictions about steric asymmetry. We exemplify the field-dependent
quantum collision dynamics with the behavior of the Ne-OCS() and
Ar-NO() systems. A comparison with the close-coupling calculations
available for the latter system [Chem. Phys. Lett. \textbf{313}, 491 (1999)]
demonstrates the model's ability to qualitatively explain the field dependence
of all the scattering features observed
Mie scattering by a charged dielectric particle
We study for a dielectric particle the effect of surplus electrons on the
anomalous scattering of light arising from the transverse optical phonon
resonance in the particle's dielectric constant. Excess electrons affect the
polarizability of the particle by their phonon-limited conductivity, either in
a surface layer (for negative electron affinity) or the conduction band (for
positive electron affinity). We demonstrate that surplus electrons shift an
extinction resonance in the infrared. This offers an optical way to measure the
charge of the particle and thus to use it in a plasma as a minimally invasive
electric probe.Comment: 5 pages, 5 figures, accepted manuscrip
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