9,644 research outputs found
Spin precession in the Dvali-Gabadadze-Porrati braneworld scenario
In this letter we work out the secular precession of the spin of a gyroscope
in geodesic motion around a central mass in the framework of the
Dvali-Gabadadze-Porrati multidimensional gravity model. Such an effect, which
depends on the mass of the central body and on the orbit radius of the
gyroscope, contrary to the precessions of the orbital elements of the orbit of
a test body, is far too small to be detected.Comment: Latex, 5 pages, no figures, no tables, 10 reference
On a new observable for measuring the Lense-Thirring effect with Satellite Laser Ranging
In this paper we present a rather extensive error budget for the difference
of the perigees of a pair of supplementary SLR satellites aimed to the
detection of the Lense-Thirring effect.Comment: LaTex2e, 14 pages, 1 table, no figures. Some changes and additions to
the abstract, Introduction and Conclusions. References updated, typos
corrected. Equation corrected. To appear in General Relativity and
Gravitatio
Plasmons in topological insulator cylindrical nanowires
We present a theoretical analysis of Dirac magneto-plasmons in topological
insulator nanowires. We discuss a cylindrical geometry where Berry phase
effects induce the opening of a gap at the neutrality point. By taking into
account surface electron wave functions introduced in previous papers and
within the random phase approximation, we provide an analytical form of the
dynamic structure factor. Dispersions and spectral weights of Dirac plasmons
are studied with varying the radius of the cylinder, the surface doping, and
the strength of an external magnetic field. We show that, at zero surface
doping, inter-band damped plasmon-like excitations form at the surface and
survive at low electron surface dopings (). Then, we
point out that the plasmon excitations are sensitive to the Berry phase gap
closure when an external magnetic field close to half quantum flux is
introduced. Indeed, a well-defined magneto-plasmon peak is observed at lower
energies upon the application of the magnetic field. Finally, the increase of
the surface doping induces a crossover from damped inter-band to sharp
intra-band magneto-plasmons which, as expected for large radii and dopings
(), approach the proper limit of a two-dimensional
surface.Comment: 18 pages, 11 figures, 2 Appendice
The impact of the new CHAMP and GRACE Earth gravity models on the measurement of the general relativistic Lense--Thirring effect with the LAGEOS and LAGEOS II satellites
Among the effects predicted by the General Theory of Relativity for the
orbital motion of a test particle, the post-Newtonian gravitomagnetic
Lense-Thirring effect is very interesting and, up to now, there is not yet an
undisputable experimental direct test of it. To date, the data analysis of the
orbits of the existing geodetic LAGEOS and LAGEOS II satellites has yielded a
test of the Lense-Thirring effect with a claimed accuracy of 20%-30%. According
to some scientists such estimates could be optimistic. Here we wish to discuss
the improvements obtainable in this measurement, in terms of reliability of the
evaluation of the systematic error and reduction of its magnitude, due to the
new CHAMP and GRACE Earth gravity models.Comment: LaTex2e, 6 pages, no figures, no tables. Paper presented at 2nd CHAMP
science meeting, Potsdam, 1-4 September 200
The effect of tides on the Sculptor dwarf spheroidal galaxy
Dwarf spheroidal galaxies (dSphs) appear to be some of the most dark matter
dominated objects in the Universe. Their dynamical masses are commonly derived
using the kinematics of stars under the assumption of equilibrium. However,
these objects are satellites of massive galaxies (e.g.\ the Milky Way) and thus
can be influenced by their tidal fields. We investigate the implication of the
assumption of equilibrium focusing on the Sculptor dSph by means of ad-hoc
-body simulations tuned to reproduce the observed properties of Sculptor
following the evolution along some observationally motivated orbits in the
Milky Way gravitational field. For this purpose, we used state-of-the-art
spectroscopic and photometric samples of Sculptor's stars. We found that the
stellar component of the simulated object is not directly influenced by the
tidal field, while the mass of the more diffuse DM halo is
stripped. We conclude that, considering the most recent estimate of the
Sculptor proper motion, the system is not affected by the tides and the stellar
kinematics represents a robust tracer of the internal dynamics. In the
simulations that match the observed properties of Sculptor, the present-day
dark-to-luminous mass ratio is within the stellar half-light radius
( kpc) and within the maximum radius of the analysed dataset
( kpc).Comment: 19 pages, 10 figures, accepted for publication in MNRAS. V3: updated
after editor comments See our playlist for simulation videos:
https://av.tib.eu/series/633/supplemental+videos+of+the+paper+the+effect+of+tides+on+the+sculptor+dwarf+spheroidal+galax
The relativistic precession of the orbits
The relativistic precession can be quickly inferred from the nonlinear polar
orbit equation without actually solving it.Comment: Accepted for publication in Astrophysics & Space Scienc
The impact of tidal errors on the determination of the Lense-Thirring effect from satellite laser ranging
The general relativistic Lense-Thirring effect can be detected by means of a
suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS
II satellites. While this observable is not affected by the orbital
perturbation induced by the zonal Earth solid and ocean tides, it is sensitive
to those generated by the tesseral and sectorial tides. The assessment of their
influence on the measurement of the parameter mu, with which the
gravitomagnetic effect is accounted for, is the goal of this paper. After
simulating the combined residual curve by calculating accurately the
mismodeling of the more effective tidal perturbations, it has been found that,
while the solid tides affect the recovery of mu at a level always well below
1%, for the ocean tides and the other long-period signals Delta mu depends
strongly on the observational period and the noise level: Delta mu(tides)
amounts to almost 2% after 7 years. The aliasing effect of K1 l=3 p=1 tide and
SRP(4241) solar radiation pressure harmonic, with periods longer than 4 years,
on the perigee of LAGEOS II yield to a maximum systematic uncertainty on
\m_{LT} of less than 4% over different observational periods. The zonal
18.6-year tide does not affect the combined residuals.Comment: 24 pages, 4 tables, 6 figures, submitted to Int. Journal of Mod.
Phys. D. Changes in auctorship, references and conten
Super-ASTROD: Probing primordial gravitational waves and mapping the outer solar system
Super-ASTROD (Super Astrodynamical Space Test of Relativity using Optical
Devices or ASTROD III) is a mission concept with 3-5 spacecraft in 5 AU orbits
together with an Earth-Sun L1/L2 spacecraft ranging optically with one another
to probe primordial gravitational-waves with frequencies 0.1 microHz - 1 mHz,
to test fundamental laws of spacetime and to map the outer solar system. In
this paper we address to its scientific goals, orbit and payload selection, and
sensitivity to gravitational waves.Comment: 7 pages, 1 figure, presented to 7th International LISA Symposium,
16-20 June 2008, Barcelona; submitted to Classical and Quantum Gravity;
presentation improve
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