30,038 research outputs found
Behavior of the sonic boom shock wave near the sonic cutoff altitude
Behavior of sonic boom shock wave near sonic cutoff altitud
Testing Einstein's time dilation under acceleration using M\"ossbauer spectroscopy
The Einstein time dilation formula was tested in several experiments. Many
trials have been made to measure the transverse second order Doppler shift by
M\"{o}ssbauer spectroscopy using a rotating absorber, to test the validity of
this formula. Such experiments are also able to test if the time dilation
depends only on the velocity of the absorber, as assumed by Einstein's clock
hypothesis, or the present centripetal acceleration contributes to the time
dilation. We show here that the fact that the experiment requires -ray
emission and detection slits of finite size, the absorption line is broadened;
by geometric longitudinal first order Doppler shifts immensely. Moreover, the
absorption line is non-Lorenzian. We obtain an explicit expression for the
absorption line for any angular velocity of the absorber.
The analysis of the experimental results, in all previous experiments which
did not observe the full absorption line itself, were wrong and the conclusions
doubtful. The only proper experiment was done by K\"{u}ndig (Phys. Rev. 129
(1963) 2371), who observed the broadening, but associated it to random
vibrations of the absorber. We establish necessary conditions for the
successful measurement of a transverse second order Doppler shift by
M\"{o}ssbauer spectroscopy. We indicate how the results of such an experiment
can be used to verify the existence of a Doppler shift due to acceleration and
to test the validity of Einstein's clock hypothesis.Comment: 11 pages, 4 figure
Third Earth Resources Technology Satellite Symposium. Volume 3: Discipline summary reports
Presentations at the conference covered the following disciplines: (1) agriculture, forestry, and range resources; (2) land use and mapping; (3) mineral resources, geological structure, and landform surveys; (4) water resources; (5) marine resources; (6) environment surveys; and (7) interpretation techniques
Third Earth Resources Technology Satellite Symposium. Volume 2: Summary of results
Summaries are provided of significant results taken from presentations at the symposium along with some typical examples of the applications of ERTS-1 data for solving resources management problems at the national, state, and local levels
The Narrow-band Ultraviolet Imaging Experiment for Wide-field Surveys (NUVIEWS)-I: Dust scattered continuum
We report on the first results of the Narrow-band Ultraviolet Imaging
Experiment for Wide-field Surveys (NUVIEWS), a sounding rocket experiment
designed to map the far-ultraviolet background in four narrow bands. This is
the first imaging measurement of the UV background to cover a substantial
fraction of the sky. The narrow band responses (145, 155, 161, and 174 nm, 7-10
nm wide) allow us to isolate background contributions from dust-scattered
continuum, H2 fluorescence, and CIV 155 nm emission. In our first flight, we
mapped one quarter of the sky with 5-10 arcminute imaging resolution. In this
paper, we model the dominant contribution of the background, dust-scattered
continuum. Our data base consists of a map of over 10,000 sq. degrees with 468
independent measurements in 6.25 by 6.25 sq. degree bins. Stars and
instrumental stellar halos are removed from the data. We present a map of the
continuum background obtained in the 174 nm telescope. We use a model that
follows Witt, Friedman, and Sasseen (1997: WFS) to account for the
inhomogeneous radiation field and multiple scattering effects in clouds. We
find that the dust in the diffuse interstellar medium displays a moderate
albedo (a=0.55+/-0.1) and highly forward scattering phase function parameter
(g=0.75+/-0.1) over a large fraction of the sky, similar to dust in star
forming regions. We also have discovered a significant variance from the model.Comment: 16 pages, 3 ps figures, submitted to Astrophysical Journal Letter
Detecting many-body entanglements in noninteracting ultracold atomic fermi gases
We explore the possibility of detecting many-body entanglement using
time-of-flight (TOF) momentum correlations in ultracold atomic fermi gases. In
analogy to the vacuum correlations responsible for Bekenstein-Hawking black
hole entropy, a partitioned atomic gas will exhibit particle-hole correlations
responsible for entanglement entropy. The signature of these momentum
correlations might be detected by a sensitive TOF type experiment.Comment: 5 pages, 5 figures, fixed axes labels on figs. 3 and 5, added
reference
The effect of uniaxial pressure on the magnetic anisotropy of the Mn_{12}-Ac single-molecule magnet
We study the effect of uniaxial pressure on the magnetic hysteresis loops of
the single-molecule magnet Mn_{12}-Ac. We find that the application of pressure
along the easy axis increases the fields at which quantum tunneling of
magnetization occurs. The observations are attributed to an increase in the
molecule's magnetic anisotropy constant D of 0.142(1)%/kbar. The increase in D
produces a small, but measurable increase in the effective energy barrier for
magnetization reversal. Density-functional theory calculations also predict an
increase in the barrier with applied pressure.Comment: version accepted by EPL; 6 pages, including 7 figures. Small changes
and added reference
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