scholarly journals Global propagation of massive quantum fields in the plane gravitational waves and electromagnetic backgrounds

2021 ◽  
Author(s):  
Krzysztof Andrzejewski ◽  
P. Kosiński
Keyword(s):  
Cross Sections ◽  
Electromagnetic Waves ◽  
Quantum Fields ◽  
Circularly Polarized ◽  
Dirac Delta ◽  
Phase Corrections ◽  
General Plane ◽  
Discrete Change ◽  
Infinite Range ◽  
Plane Gravitational Waves

Abstract The behavior of massive quantum fields in the general plane wave spacetime and external, non-plane, electromagnetic waves is studied. The asymptotic conditions, the ``in" (``out") states and the cross sections are analysed. It is observed that, despite of the singularities encountered, the global form of these states can be obtained: at the singular points the Dirac delta-like behavior emerges and there is a discrete change of phase of the wave function after passing through each singular point. The relations between these phase corrections and local charts are discussed. Some examples of waves of infinite range (including the circularly polarized ones) are presented for which the explicit form of solutions can be obtained. All these results concern both the scalar as well as spin one-half fields; in latter case the change of the spin polarization after the general sandwich wave has passed is studied.

Gravitational waves in general relativity III. Exact plane waves

1959 ◽  
Vol 251 (1267) ◽  
pp. 519-533 ◽  
Keyword(s):  
Plane Wave ◽  
Gravitational Waves ◽  
Electromagnetic Waves ◽  
Plane Waves ◽  
Flat Space ◽  
Field Equations ◽  
Test Particles ◽  
Wave Space ◽  
General Plane ◽  
Plane Gravitational Waves

Plane gravitational waves are here defined to be non-flat solutions of Einstein’s empty spacetime field equations which admit as much symmetry as do plane electromagnetic waves, namely, a 5-parameter group of motions. A general plane-wave metric is written down and the properties of plane wave space-times are studied in detail. In particular, their characterization as 4 plane ’ is justified further by the construction of 4 sandwich waves ’ bounded on both sides by (null) hyperplanes in flat space-time. It is shown that the passing of a sandwich wave produces a relative acceleration in free test particles, and inferred from this that such waves transport energy.

Disorientation of Cs(62P1/2) atoms, induced in collisions with noble gases

1976 ◽  
Vol 54 (7) ◽  
pp. 748-752 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Buffer Gas ◽  
Resonance Fluorescence ◽  
Circularly Polarized ◽  
Low Field ◽  
Good Agreement ◽  
Gas Pressures

The disorientation of 62P1/2 cesium atoms, induced in collisions with noble gas atoms in their ground states, was systematically investigated by monitoring the depolarization of cesium resonance fluorescence in relation to noble gas pressures. The Cs atoms, contained together with a buffer gas in a fluorescence cell and located in zero magnetic field, were excited and oriented by irradiation with circularly polarized 8943 Å resonance radiation, and the resonance fluorescence, emitted in an approximately backward direction, was analyzed with respect to circular polarization. The experiments yielded the following disorientation cross sections which have been corrected for the effects of nuclear spin: Cs–He: 4.9 ± 0.7 Å2; Cs–Ne: 2.1 ± 0.3 Å2; Cs–Ar: 5.6 ± 0.8 Å2; Cs–Kr: 5.8 ± 0.9 Å2; Cs–Xe: 6.3 ± 0.9 Å2. The results are in good agreement with most of the available zero-field and low-field data.

scholarly journals Electromagnetic Waves Through Disordered Systems: Comparison of Intensity, Transmission and Conductance

2001 ◽  
Vol 694 ◽  
Author(s):  
Fredy R Zypman ◽  
Gabriel Cwilich
Keyword(s):  
Probability Distribution ◽  
Disordered Systems ◽  
Electromagnetic Waves ◽  
Delta Function ◽  
Rayleigh Distribution ◽  
Dirac Delta Function ◽  
Universal Form ◽  
Dirac Delta ◽  
Diffusive Regime ◽  
Analytical Expressions

AbstractWe obtain the statistics of the intensity, transmission and conductance for scalar electromagnetic waves propagating through a disordered collection of scatterers. Our results show that the probability distribution for these quantities x, follow a universal form, YU(x) = xne−xμ. This family of functions includes the Rayleigh distribution (when α=0, μ=1) and the Dirac delta function (α →+ ∞), which are the expressions for intensity and transmission in the diffusive regime neglecting correlations. Finally, we find simple analytical expressions for the nth moment of the distributions and for to the ratio of the moments of the intensity and transmission, which generalizes the n! result valid in the previous case.

scholarly journals The Effect of Attenuation from Fish Shoals on Long-Range, Wide-Area Acoustic Sensing in the Ocean

2019 ◽  
Vol 11 (21) ◽  
pp. 2464 ◽  
Author(s):  
Daniel Duane ◽  
Byunggu Cho ◽  
Ankita D. Jain ◽  
Olav Rune Godø ◽  
Nicholas C. Makris
Keyword(s):  
Remote Sensing ◽  
Long Range ◽  
Cross Sections ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Wide Area ◽  
Line Transect ◽  
Acoustic Sensing ◽  
Underwater Acoustic ◽  
Primary Means

Acoustics is the primary means of long-range and wide-area sensing in the ocean due to the severe attenuation of electromagnetic waves in seawater. While it is known that densely packed fish groups can attenuate acoustic signals during long-range propagation in an ocean waveguide, previous experimental demonstrations have been restricted to single line transect measurements of either transmission or backscatter and have not directly investigated wide-area sensing and communication issues. Here we experimentally show with wide-area sensing over 360° in the horizontal and ranges spanning many tens of kilometers that a single large fish shoal can significantly occlude acoustic sensing over entire sectors spanning more than 30° with corresponding decreases in detection ranges by roughly an order of magnitude. Such blockages can comprise significant impediments to underwater acoustic remote sensing and surveillance of underwater vehicles, marine life and geophysical phenomena as well as underwater communication. This makes it important to understand the relevant mechanisms and accurately predict attenuation from fish in long-range underwater acoustic sensing and communication. To do so, we apply an analytical theory derived from first principles for acoustic propagation and scattering through inhomogeneities in an ocean waveguide to model propagation through fish shoals. In previous experiments, either the attenuation from fish in the shoal or the scattering cross sections of fish in the shoal were measured but not both, making it impossible to directly confirm a theoretical prediction on attenuation through the shoal. Here, both measurements have been made and they experimentally confirm the waveguide theory presented. We find experimentally and theoretically that attenuation can be significant when the sensing frequency is near the resonance frequency of the shoaling fish. Negligible attenuation was observed in previous low-frequency ocean acoustic waveguide remote sensing (OAWRS) experiments because the sensing frequency was sufficiently far from the swimbladder resonance peak of the shoaling fish or the packing densities of the fish shoals were not sufficiently high. We show that common heuristic approaches that employ free space scattering assumptions for attenuation from fish groups can lead to significant errors for applications involving long-range waveguide propagation and scattering.

Whistler instability in plasmas with anisotropic and non-Maxwellian velocity distributions

1971 ◽  
Vol 6 (3) ◽  
pp. 449-456 ◽  
Author(s):  
Kai Fong Lee
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Maxwell Equations ◽  
Transverse Velocity ◽  
Distribution Functions ◽  
Loss Cone ◽  
Circularly Polarized ◽  
Electron Plasmas ◽  
Thermal Spread ◽  
The Magnetic Field

The instability of right-handed, circularly polarized electromagnetic waves, propagating along an external magnetic field (whistler mode), is studied for electron plasmas with distribution functions peaked at some non-zero value of the transverse velocity. Based on the linearized Vlasov-Maxwell equations, the criteria for instability are given both for non-resonant instabilities arising from distribution functions with no thermal spread parallel to the magnetic field, and for resonant instabilities arising from distribution functions with Maxwellian dependence in the parallel velocities. It is found that, in general, the higher the average perpendicular energy, the more is the plasma susceptible to the whistler instability. These criteria are then applied to a sharply peaked ring distribution, and to loss-cone distributions of the Dory, Guest & Harris (1965) type.

Double passage of electromagnetic waves through magnetized plasma: approximation of independent normal waves

Open Physics ◽  
2010 ◽  
Vol 8 (3) ◽  
Author(s):  
Yury Kravtsov ◽  
Bohdan Bieg
Keyword(s):  
Electromagnetic Wave ◽  
Characteristic Feature ◽  
Electromagnetic Waves ◽  
Polarization State ◽  
Normal Modes ◽  
Practical Interest ◽  
Magnetized Plasma ◽  
Fast Wave ◽  
Circularly Polarized ◽  
Normal Waves

AbstractPolarization properties of electromagnetic waves, double-passed through magnetized plasma, are studied. Analyses are performed in the case of non-interacting normal modes, propagating in homogeneous and weakly inhomogeneous plasmas, and for three kinds of reflectors: metallic plane, 2D corner retro-reflector (2D-CR), and cubic corner retro-reflector (CCR). It is shown that an electromagnetic wave, reflected from a metallic plane and from a CCR, contains only “velocity-preserving” channels, whose phases are doubled in comparison with those of a single-passage propagation. At the same time, an electromagnetic wave reflected from a 2D-CR is shown to contain both “velocity-preserving” and “velocity-converting” channels, the latter converting the fast wave into the slow one and vice-versa. One characteristic feature of “velocity-converting” channels is that they reproduce the initial polarization state near the source, which might be of practical interest for plasma interferometry. In the case of circularly polarized modes, “velocity-preserving” channels completely disappear, and only “velocity-converting” channels are to be found.

scholarly journals Modeling and Simulation of stochastically deformed Waveguides using Schelkunoff's Method

2018 ◽  
Vol 16 ◽  
pp. 35-41
Author(s):  
Hoang Duc Pham ◽  
Soeren Ploennigs ◽  
Wolfgang Mathis
Keyword(s):  
Cross Sections ◽  
Electromagnetic Waves ◽  
Analytic Solution ◽  
Propagation Constant ◽  
Circular Waveguide ◽  
Transverse Field ◽  
Field Pattern ◽  
Coupled Mode ◽  
Special Cases ◽  
Cylindrical Waveguides

Abstract. This paper deals with the propagation of electromagnetic waves in cylindrical waveguides with irregularly deformed cross-sections. The general theory of electromagnetic waves is of high interest because of its practical use as a transmission medium. But only in a few special cases, an analytic solution of Maxwell's equations and the appropriate boundary conditions can be found (Spencer, 1951). The coupled-mode theory, also known as Schelkunoff's method, is a semi-numerical method for computing electromagnetic waves in hollow and cylindrical waveguides bounded by perfect electric walls (Saad, 1985). It allows to calculate the transverse field pattern and the propagation constant. The aim of this paper is to derive the so-called generalized telegraphist's equations for irregular deformed waveguides. Subsequently, the method's application will be used on a circular waveguide as an illustrating example.

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