30,338 research outputs found
Making electromagnetic wavelets
Electromagnetic wavelets are constructed using scalar wavelets as
superpotentials, together with an appropriate polarization. It is shown that
oblate spheroidal antennas, which are ideal for their production and reception,
can be made by deforming and merging two branch cuts. This determines a unique
field on the interior of the spheroid which gives the boundary conditions for
the surface charge-current density necessary to radiate the wavelets. These
sources are computed, including the impulse response of the antenna.Comment: 29 pages, 4 figures; minor corrections and addition
A low-frequency radio survey of the planets with RAE-2
Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025 to 13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE-2
Solution of Einstein’s Causality Problem: The AHK Theorem
'Chance' is defined as an event on the time scale withour any cause before it appears. That means, that cause and effect is identical. This is the only way to integrate chance into a consistent theory of causality. The identity of cause and effect is called AHK theorem (Aristotle-Hegel-Kaiser)
The solar elogation distribution of low frequency radio bursts
Over 500 days of low frequency (less than 5 MHz) radio observations from the IMP-6 spacecraft were accumulated to produce a two dimensional map (frequency versus elongation) of solar type III burst occurrences. This map indicates that most solar bursts are emitted at the second harmonic of the plasma frequency rather than the fundamental. The map also shows that the solar wind electron density varies
MARKET IMPACTS OF BOVINE SOMATROPIN: A SUPPLY AND DEMAND ANALYSIS
The potential economic impacts of the introduction of bovine somatotropin (bST) on U.S. milk supply and demand are analyzed using a national model of Class I and Class II milk markets. The results indicate that the introduction of bST will lead to lower milk prices, higher milk production, and larger government purchases of dairy products. Unlike previous economic analyses of bST, this analysis considers both supply and demand effects of bST. The implication is that studies that ignore potential demand-side effects may produce misleading results.Demand and Price Analysis,
AN ANNOTATIVE BIBLIOGRAPHY OF RESEARCH ON THE ECONOMIC EFFECTS OF CLIMATE CHANGE ON AGRICULTURE
Anthropogenic emissions of carbon dioxide and other "greenhouse" gases have the potential to substantially warm climates worldwide. While the timing and magnitude of global warming is uncertain, scientists on the Intergovernmental Panel on Climate Change (IPCC) predict that average global temperature may increase by 1.5- 4.5³C (2.7-8.1³F) over the next 100 years. Changes in precipitation will likely accompany any changes in temperature. However, the magnitude, and even direction of these changes is difficult to predict with much confidence on a regional basis. The agricultural sector may be profoundly affected by future changes in temperature, precipitation, solar radiation, and carbon dioxide concentrations. Over the past decade, there has been a growing body of research examining the potential impacts of climate change on agriculture. The purpose of this paper is to report and summarize recent research on the potential economic impacts of global climate change on agriculture. To that end, an annotative bibliography of articles is presented in this paper.Environmental Economics and Policy,
Dominant -exchange nucleon-nucleon interaction: Spin-spin and tensor potentials
We calculate at two-loop order in chiral perturbation theory the
electromagnetic corrections to the two-pion exchange nucleon-nucleon
interaction that is generated by the isovector spin-flip
contact-vertex proportional to the large low-energy constant GeV. We find that the respective -exchange potentials
contain sizeable isospin-breaking components which reach up to -4% of
corresponding isovector -exchange potentials. The typical values of these
novel charge-independence breaking spin-spin and tensor potentials are MeV and MeV, at a nucleon distance of fm. The
charge-symmetry breaking spin-spin and tensor potentials come out a factor of
2.4 smaller. Our analytical results for these presumably dominant
isospin-violating spin-spin and tensor NN-forces are in a form such that they
can be easily implemented into phase-shift analyses and few-body calculations.Comment: 7 pages, 1 figure, 2 tables, to be published in Physical Review C:
Brief report
Electromagnetic corrections to the dominant two-pion exchange nucleon-nucleon potential
We calculate at two-loop order in chiral perturbation theory the
electromagnetic corrections to the dominant two-pion exchange nucleon-nucleon
interaction that is generated by the isoscalar contact-vertex
proportional to the large low-energy constant . We find that the
respective -exchange potential contains sizeable isospin-breaking
components which amount to about -1% of the strongly attractive isoscalar
central -exchange potential. The typical value of these novel
charge-independence and charge-symmetry breaking central potentials is MeV at a nucleon distance of fm. Our analytical result
for this presumably dominant -exchange interaction is in a form
such that it can be easily implemented into phase-shift analyses and few-body
calculations.Comment: 7 pages, 1 figure, to be published in Physical Review C (2006): Brief
Report
Decay dynamics in the coupled-dipole model
Cooperative scattering in cold atoms has gained renewed interest, in
particular in the context of single-photon superradiance, with the recent
experimental observation of super-and subradiance in dilute atomic clouds.
Numerical simulations to support experimental signatures of cooperative
scattering are often limited by the number of dipoles which can be treated,
well below the number of atoms in the experiments. In this paper, we provide
systematic numerical studies aimed at matching the regime of dilute atomic
clouds. We use a scalar coupled-dipole model in the low excitation limit and an
exclusion volume to avoid density-related effects. Scaling laws for super-and
subradiance are obtained and the limits of numerical studies are pointed out.
We also illustrate the cooperative nature of light scattering by considering an
incident laser field, where half of the beam has a phase shift. The
enhanced subradiance obtained under such condition provides an additional
signature of the role of coherence in the detected signal
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