Group velocity and propagation of numerical errors

1972 ◽  
Author(s):  
C. KENTZER
Keyword(s):  
Group Velocity ◽  
Numerical Errors

Current status of special planetary and lunar theories and ephemerides

1966 ◽  
Vol 25 ◽  
pp. 266-267
Author(s):  
R. L. Duncombe
Keyword(s):  
Observational Data ◽  
Current Status ◽  
Numerical Errors

An examination of some specialized lunar and planetary ephemerides has revealed inconsistencies in the adopted planetary masses, the presence of non-gravitational terms, and some outright numerical errors. They should be considered of temporary usefulness only, subject to subsequent amendment as required for the interpretation of observational data.

Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions

1990 ◽  
Vol 48 (2) ◽  
pp. 110-111 ◽  
Author(s):  
F. Hasselbach ◽  
A. Schäfer
Keyword(s):  
Group Velocity ◽  
Wave Packets ◽  
Index Of Refraction ◽  
Electron Wave ◽  
Fringe Contrast ◽  
Faraday Cage ◽  
Optical Index ◽  
Wien Filter ◽  
Coherent Wave ◽  
Electric And Magnetic Fields

Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

The four-dimensional group velocity

1978 ◽  
Vol 125 (7) ◽  
pp. 549-565 ◽  
Author(s):  
V.G. Polevoi ◽  
S.M. Rytov
Keyword(s):  
Group Velocity ◽  
Dimensional Group

ESTIMATION OF THOMSEN'S EPSILON AND DELTA IN A SINGLE CORE USING ULTRASONIC PHASE AND GROUP VELOCITY MEASUREMENTS

2019 ◽  
Author(s):  
Gabriel Gallardo-Giozza ◽  
D. Nicolás Espinoza ◽  
Carlos Torres-Verdín ◽  
Elsa Maalouf
Keyword(s):  
Group Velocity ◽  
Velocity Measurements

Negative Group Velocity of Surface Polaritons in Metal Foil Nanostructure

2017 ◽  
Vol 9 (3) ◽  
pp. 03039-1-03039-4 ◽  
Author(s):  
Y. M. Aleksandrov ◽  
◽  
V. V. Yatsishen ◽  
Keyword(s):  
Group Velocity ◽  
Metal Foil ◽  
Negative Group ◽  
Surface Polaritons ◽  
Negative Group Velocity
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