Search results for "waves"

Polarization in p-p and $$\bar p - p$$ elastic scatteringelastic scattering

1970

Elastic pion scattering on the deuteron in a multiple scattering model

1996

Pion elastic scattering on deuterium is studied in the KMT multiple scattering approach developed in momentum space. Using a Paris wave function and the same methods and approximations as commonly used in pion scattering on heavier nuclei excellent agreement with differential cross section data is obtained for a wide range of pion energies. Only for $T_{\pi}>250$ MeV and very backward angles, discrepancies appear that are reminiscent of disagreements in pion scattering on $^3$He, $^3$H, and $^4$He. At low energies the second order corrections have been included. Polarization observables are studied in detail. While tensor analyzing powers are well reproduced, vector analyzing powers exhibit…

�ber die Abh�ngigkeit des Polarisationsgrades vom Streuwinkel bei Mott-Streuung langsamer Elektronen

1965

The angular dependence of polarizationP(Θ) of electrons elastically scattered by a beam of mercury atoms is measured in a double scattering experiment for electron energies of 0,9; 1,2; and 1,5 keV. The results are compared with theory and found to be in good agreement. Maximum degree of polarization measured isP=0,53±0,10 (electron current 10−12A).

A PROJECT-POSED APPROACH TO REAL BODY DYNAMICS: THE ROLE OF CONSTRAINTS IN ELASTIC WAVE PROPAGATION

2010

In this paper we present some results of a project-posed approach to the teaching of mechanical wave propagation focused on observations and measurements of wave properties in solids and on modelling of these properties by using different simulation tools. In particular, the propagation speed of sound waves in metallic rods is studied by using simple experimental arrangements based on the measurements of contact times between a small body and long metallic rods with which the body can collide. An interesting effect of this approach is the revision of students’ ideas about the rigid body model, studied at high school or college level and usually hardly followed by deepening on the fundamenta…

No effects of pulsed radio frequency electromagnetic fields on melatonin, cortisol, and selected markers of the immune system in man.

2001

There is growing public concern that radio frequency electromagnetic fields may have adverse biological effects. In the present study eight healthy male students were tested to see whether or not radio frequency electromagnetic fields as used in modern digital wireless telecommunication (GSM standard) have noticeable effects on salivary melatonin, cortisol, neopterin, and immunoglobulin A (sIgA) levels during and several hours after exposure. In a specifically designed, shielded experimental chamber, the circularly polarized electromagnetic field applied was transmitted by an antenna positioned 10 cm behind the head of upright sitting test persons. The carrier frequency of 900 MHz was pulse…

Communication modes in vector diffraction

2010

The communication modes, which mathematically correspond to singular value decomposition, have proven a useful concept in optical scalar-field diffraction, with applications in resolution studies, image synthesis, and wave propagation. For optical near-field geometries the communication modes have to be extended to electromagnetic field accounting for the polarization properties. In this paper we present the vector-valued communication modes method based on the rigorous electric-field diffraction integral. As a special case the transverse-electric scalar field modes are obtained. The intensity and polarization properties of the leading electromagnetic communication modes in near-field arran…

Electromagnetic field fluctuations near a dielectric-vacuum boundary and surface divergences in the ideal conductor limit

2012

We consider the electric and magnetic field fluctuations in the vacuum state in the region external to a half-space filled with a homogeneous non-dissipative dielectric. We discuss an appropriate limit to an ideal metal and concentrate our interest on the renormalized field fluctuations, or equivalently to renormalized electric and magnetic energy densities, in the proximity of the dielectric-vacuum interface. We show that surface divergences of field fluctuations arise at the interface in an appropriate ideal conductor limit, and that our limiting procedure allows to discuss in detail their structure. Field fluctuations close to the surface can be investigated through the retarded Casimir-…

Biorthonormal-basis method for the vector description of optical-fiber modes

1998

This paper gives the theoretical basis for the development of real vector modal methods to describe optical-fiber modes. To this end, the vector wave equations, which determine the electromagnetic fields, are written in terms of a pair of linear, nonself-adjoint operators, whose eigenvectors satisfy biorthogonality relations. The key of our method is to obtain a matrix representation of the vector wave equations in a basis that is defined by the modes of an auxiliary system. Our proposed technique can be applied to fibers with any profile, even those with a complex refractive index. An example is discussed to illustrate our approach.

Computation of the field diffracted by a local surface defect: application to tip–sample interaction in the photon scanning tunneling microscope

1996

We use a method based on the Fourier transform of the electromagnetic field to compute the field diffracted by a local deformation of a plane boundary surface. We give a complete development of each step of the technique. To show the interaction that exists between the probe of a near-field optical microscope and the observed sample, we use the model of a truncated cone-shaped tip above a rectangular surface defect. We compute the electrical intensity along a line located between the tip and the local surface defect. We show the influence of the polarization of the incident wave and the effect of the position of the tip with respect to the position of the surface defect.

The electromagnetic group: Bosonic BRST charge

1990

Abstract We give an infinite-dimensional Lie group from which a group approach to quantization (GAQ) derives a Gupta-Bleuler-like quantization for the electromagnetic field. The incorporation into the group law of the gauge transformation properties of Aμ(x), Aμ(x) → Aμ(x) + ∂μφ, requires a non-conventional generator which is related to the BRST charge.