549 research outputs found
Satellite gravitational orbital perturbations and the gravitomagnetic clock effect
In order to detect the gravitomagnetic clock effect by means of two
counter-orbiting satellites placed on identical equatorial and circular orbits
around the Earth with radius 7000 km their radial and azimuthal positions must
be known with an accuracy of delta r =10^{-1} mm and delta phi =10^{-2} mas per
revolution. In this work we investigate if the radial and azimuthal
perturbations induced by the dynamical and static parts of the Earth' s
gravitational field meet this requirements. While the radial direction is
affected only by harmonic perturbations with periods up to some tens of days,
the azimuthal location is perturbed by a secular drift and very long period
effects.It results that the present level of accuracy in the knowledge both of
the Earth solid and ocean tides, and of the static part of the geopotential
does not allow an easy detection of the gravitomagnetic clock effect, at least
by using short arcs only.Comment: 18 pages, 4 figures. Submitted to Int. Journal of Mod. Phys.
A Gravitomagnetic Effect on the Orbit of a Test Body due to the Earth's Variable Angular Momentum
The well known general relativistic Lense-Thirring drag of the orbit of a
test particle in the stationary field of a central slowly rotating body is
generated, in the weak-field and slow-motion approximation of General
Relativity, by a gravitomagnetic Lorentz-like acceleration in the equations of
motion of the test particle. In it the gravitomagnetic field is due to the
central body's angular momentum supposed to be constant. In the context of the
gravitational analogue of the Larmor theorem, such acceleration looks like a
Coriolis inertial term in an accelerated frame. In this paper the effect of the
variation in time of the central body's angular momentum on the orbit of a test
mass is considered. It can be shown that it is analogue to the inertial
acceleration due to the time derivative of the angular velocity vector of an
accelerated frame. The possibility of detecting such effect in the
gravitational field of the Earth with LAGEOS-like satellites is investigated.
It turns out that the orbital effects are far too small to be measured.Comment: LaTex2e, 1 table, no figures, 7 page
MEASURING GRAVITOMAGNETIC EFFECTS BY MEANS OF RING LASERS
Light is a good probe for general relativistic effects. Exploiting the asymmetry of the propagation in the vicinity of a central rotating mass it is possible to use a ring laser in order to measure the frame dragging of the reference frames by the gravitational field of the Earth (Lense-Thirring effect). I shall present the G-GranSasso experiment whose objective is precisely to measure the Lense-Thirring and the de Sitter effects in a terrestrial laboratory. The experimental apparatus will be made of a set of at least three, differently oriented, ring lasers rigidly attached to a central "monument". The signal will be in the form of the beat frequency produced in the annular cavity of each laser by the rotational anisotropy. The laboratory will be located underground in the Laboratori Nazionali del Gran Sasso facility, in Italy. The required sensitivity is just one order of magnitude below the performance of the best existing instruments and the new design will attain i
Can Solar System observations tell us something about the cosmological constant?
In this note we show that the latest determinations of the residual Mercury's
perihelion advance, obtained by accounting for almost all known Newtonian and
post-Newtonian orbital effects, yields only very broad constraints on the
cosmological constant. Indeed, from \delta\dot\omega=-0.0036 + - 0.0050
arcseconds per century one gets -2 10^-34 km^-2 < Lambda < 4 10^-35 km^-2. The
currently accepted value for Lambda, obtained from many independent
cosmological and large-scale measurements, amounts to almost 10^-46 km^-2.Comment: Latex2e, 4 pages, 2 table, no figures, 11 references. Table 2 added,
typos in the units of Lambda correcte
External Factors Affecting the Performance of Micro and Small Enterprises (MSES): a Study on Selected MSEs in Bedele Town
The study was designed to assess the external factors affecting the performance of Micro and
Small Enterprises (MSEs) in Bedele town. A sample of 297 operators or owners of the
enterprises engaged in five sectors was taken for the study using stratified random sampling
technique. The head of Bedele micro and small enterprises development agency was purposely
selected for the interview. From the distributed 297 questionnaires 269 were returned. The
data collected through questionnaire is analyzed using both descriptive and inferential
analysis (Pearson's product moment correlation coefficient and Multiple Linear Regression
Model). Besides, the interview questions were analyzed using descriptive narrations. The
empirical finding elucidated that factors affect the performance of MSEs which include;
accessibility of external source of finance, accessibility of business development services and
marketing factors are significantly affect the performance of micro and small enterprises in
Bedele town. While, government policy and bureaucracy and infrastructure are found to be
insignificantly explaining the performance of MSEs. The finding further indicate that, the
existence of linear and positive significant, ranging from weak to strong relationship was
found between independent variables and dependent variable. Based on the findings
recommendations to stakeholders, to operators of MSEs and suggestions for further
researchers are forwarded.Jimma Universit
Gravitomagnetic time delay and the Lense-Thirring effect in Brans-Dicke theory of gravity
We discuss the gravitomagnetic time delay and the Lense-Thirring effect in
the context of Brans-Dicke theory of gravity. We compare the theoretical
results obtained with those predicted by general relativity. We show that
within the accuracy of experiments designed to measure these effects both
theories predict essentially the same result.Comment: 10 pages Typeset using REVTE
Glaciation in Montana
Glacial deposits are increasingly entering into consideration in engineering projects, soil surveys, ground-water supply, sources for industrial materials, and other economic enterprises. In the field of engineering, glacial deposits if present must be considered in connection with reservoir sites, dam or bridge abutments, road building, and other types of construction work
Trajectory of test particle around a slowly rotating relativistic star emitting isotropic radiation
We explored the motion of test particles near slowly rotating relativistic
star having a uniform luminosity. In order to derive the test particle's
equations of motion, we made use of the radiation stress-energy tensor first
constructed by Miller and Lamb \cite{ML96}. From the particle's trajectory
obtained through the numerical integration of the equations of motion, it is
found that for sufficiently high luminosity, "suspension orbit" exists, where
the test particle hovers around at uniform angular velocity in the same
direction as the star's spin. Interestingly, it turned out that the radial
position of the "suspension orbit" was determined by the luminosity and the
angular momentum of the star alone and was independent of the initial positions
and the specific angular momentum of the particle. Also found is that there
exist not only the radiation drag but also "radiation counter-drag" which
depends on the stellar radius and the angular momentum and it is this radiation
counter-drag that makes the test particle in the "suspension orbit" to hover
around at uniform angular velocity which is greater than that induced by the
Lense-Thirring effect (i.e., general relativistic dragging of inertial frame).Comment: 23 pages, 7 figures, to appear in Phys. Rev. D
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