334 research outputs found
On detecting the gravitomagnetic field of the earth by means of orbiting clocks
Based on the recent finding that the difference in proper time of two clocks
in prograde and retrograde equatorial orbits about the Earth is of the order
10^{-7}s per revolution, the possibility of detecting the terrestrial
gravitomagnetic field by means of clocks carried by satellites is discussed. A
mission taking advantage of this influence of the rotating Earth on the proper
time is outlined and the conceptual difficulties are briefly examined.Comment: Talk given at the 32nd COSPAR Scientific Assembly, held at Nagoya,
Japan, 12-19 July 1998, 4 pages LATE
An alternative derivation of the gravitomagnetic clock effect
The possibility of detecting the gravitomagnetic clock effect using
artificial Earth satellites provides the incentive to develop a more intuitive
approach to its derivation. We first consider two test electric charges moving
on the same circular orbit but in opposite directions in orthogonal electric
and magnetic fields and show that the particles take different times in
describing a full orbit. The expression for the time difference is completely
analogous to that of the general relativistic gravitomagnetic clock effect in
the weak-field and slow-motion approximation. The latter is obtained by
considering the gravitomagnetic force as a small classical non-central
perturbation of the main central Newtonian monopole force. A general expression
for the clock effect is given for a spherical orbit with an arbitrary
inclination angle. This formula differs from the result of the general
relativistic calculations by terms of order c^{-4}.Comment: LaTex2e, 11 pages, 1 figure, IOP macros. Submitted to Classical and
Quantum Gravit
Superfluid 4He dynamics beyond quasiparticle excitations
The dynamics of superfluid 4He at and above the Landau quasiparticle regime
is investigated by high precision inelastic neutron scattering measurements of
the dynamic structure factor. A highly structured response is observed above
the familiar phonon-maxon-roton spectrum, characterized by sharp thresholds for
phonon-phonon, maxon-roton and roton-roton coupling processes. The experimental
dynamic structure factor is compared to the calculation of the same physical
quantity by a Dynamic Many-body theory including three-phonon processes
self-consistently. The theory is found to provide a quantitative description of
the dynamics of the correlated bosons for energies up to about three times that
of the Landau quasiparticles.Comment: 5 pages, 3 figure
Gravitomagnetism, clocks and geometry
New techniques to evaluate the clock effect using light are described. These
are based on the flatness of the cylindrical surface containing the world lines
of the rays constrained to move on circular trajectories about a spinning mass.
The effect of the angular momentum of the source is manifested in the fact that
inertial observers must be replaced by local non rotating observers. Starting
from this an exact formula for circular trajectories is found. Numerical
estimates for the Earth environment show that light would be a better probe
than actual clocks to evidence the angular momentum influence. The advantages
of light in connection with some principle experiments are shortly reviewed.Comment: TCI Latex, 12 pages, 2 figures. To appear in European Journal of
Physic
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