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[en] Spin rotation of spin-1/2 particles involved in planar channeling in straight and bent crystals is described in a consistent quantum mechanical manner. This is done by solving the Dirac equation in the Foldy-Wouthuysen representation, constructing an operator equation of motion for the spin, and calculating the average value of the spin precession frequency. For the case of channeling in bent crystals agreement is observed between the classical and quantum mechanical expressions, provided that the field of the planes is approximated by a harmonic potential. The effect of spin rotation in straight crystals is also examined. 17 refs
[en] The rarely mentioned fact that a pure boost in general distorts the axes of the boosted frame is shown to influence significantly the Thomas precession effect as observed in the laboratory frame. As a result the Thomas precession appears to be accompanied by a ‘wobbling’ motion of the axes of precessing rest frame connected with a moving particle. A simple method to get an exact solution for the development of the orientation of the frame axes in the case of uniform rotation of the particle is given. This is equivalent to finding the orientation of the spin vector used in the BMT theory. The discrepancy known from the literature in describing the spin, as performing a uniform rotation or as revealing in the same situation some additional oscillatory behaviour, is explained by pointing out two conceptually different approaches, ‘hybrid’ and fully consistent, in presenting the Thomas precession. (paper)
[en] New pulse timing results are given for six of the pulsars reported by Davies et al. following one or two years of observation at 430 MHz. Additional observations of pulsar JP 1953 have resulted in a spin-down age measurement (P/P) of 8.6 +- 1.3 x 109 years. A speedup of about one part in 109 has occurred in pulsar 1906+00, commencing in 1974 April with a relaxation time of about 37 days
[en] The Centrifuge Procession Analyzer (CPA) is a microcomputer-based instrument which detects precession motion in a gas centrifuge machine and calculates the amplitude and frequency of precession. The CPA consists of a printed circuit board which contains signal-conditioning circuitry and a 24-bit counter and an INTEL iSBC 80/24 single/board computer. Pression motion is detected by monitoring a signal generated by a variable reluctance pick-up coil in the top of the centrifuge machine. This signal is called a Fidler signal. The initial Fidler signal triggers a counter which is clocked by a high-precision, 20.000000-MHz, temperature-controlled, crystal oscillator. The contents of the counter are read by the computer and the counter reset after every ten Fidler signals. The speed of the centrifuge machine and the amplitude and frequency of precession are calculated and the results are displayed on a liquid crystal display on the front panel of the CPA. The report contains results from data generated by a Fidler signal simulator and data taken when the centrifuge was operated under three test conditions: (1) nitrogen gas during drive-up, steady state, and drive-down; (2) xenon gas during slip test, steady state, and the addition of gas; and (3) no gas during steady state. The qualitative results were consistent with experience with centrifuge machines using UF6 in that the amplitude of precession increased and the frequency of precession decreased during drive-up, drive-down and the slip check. The magnitude of the amplitude and frequency of precession were proportional to the molecular weight of the gases in steady state
[en] We report the serendipitous discovery of a disk-eclipse system OGLE-LMC-ECL-11893. The eclipse occurs with a period of 468 days, a duration of about 15 days, and a deep (up to ΔmI ≈ 1.5), peculiar, and asymmetric profile. A possible origin of such an eclipse profile involves a circumstellar disk. The presence of the disk is confirmed by the H-α line profile from the follow-up spectroscopic observations, and the star is identified as Be/Ae type. Unlike the previously known disk-eclipse candidates, the eclipses of OGLE-LMC-ECL-11893 retain the same shape throughout the span of ∼17 yr (13 orbital periods), indicating no measurable orbital precession of the disk.
[en] The frequency of precession of an orbital gyroscope, using a scalar theory of gravitation developed in previous papers, is calculated. In those papers it has been demonstrated that the scalar theory proposed can explain the four 'crucial tests' of relativity, and also it is compatible with the present observational astronomical data (i.e., the expansion of the universe). By comparing the precession frequency obtained with this theory with the Einstein's result a difference is observed and therefore the gyroscope experiment could be used to decide wich theory agrees with reality
[en] The Transiting Exoplanet Survey Satellite (TESS) recently observed 18 transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6 ± 11.7 s earlier than had been predicted, based on data stretching back to 2007. This is unlikely to be the result of a clock error, because TESS observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with a constant period, ruling out an 81.6 s offset at the 6.4σ level. The 1.3 day orbital period of WASP-4b appears to be decreasing at a rate of ms per year. The apparent period change might be caused by tidal orbital decay or apsidal precession, although both interpretations have shortcomings. The gravitational influence of a third body is another possibility, though at present there is minimal evidence for such a body. Further observations are needed to confirm and understand the timing variation.
[en] It is shown that for a solid body following a curvilinear trajectory its rotation angle due to the effect of the special theory of relativity (Thomson precession) is numerically equal to the rest-frame-observed solid angle through which the body-fixed axis turns as a consequence of the rotation change the body image undergoes due to Lorentz length contraction and the retardation of the light emitted by various portions of the body. In classical mechanics, the same relation connects the solid-body rotation angle to the actual solid angle that the body-fixed axis describes as the body performs a conical motion - which is a consequence of Ishlinskii's theorem. (methodological notes)