8 research outputs found
The GEO600 project
GEO600, an interferometric gravitational-wave detector with an arm length of 600 m, is currently being built in northern Germany close to Hannover. GEO600 incorporates an externally modulated fourfold delay-line Michelson interferometer giving a round-trip optical length of 2400 m. A master - slave combination of a monolithic diode-pumped Nd:YAG ring laser and an injection-locked amplifier will give a light power of about 10 W at a wavelength of 1064 nm. Power recycling increases the light power inside the interferometer to a level of about 10 kW. The use of both power and signal recycling will yield a sensitivity of the same order of magnitude as the first stages of the other large-scale gravitational-wave detectors LIGO and VIRGO currently under construction. High signal recycling factors allow the sensitivity to be increased at a chosen frequency while reducing the bandwidth of the detector. This gives an advantage over broad-band detectors in detecting narrow-band periodic sources such as pulsars. The 25 cm diameter mirrors will be suspended as double pendulums from a platform supported by vibration-reduction systems. The passive filtering properties of this system sufficiently reduce the seismic noise in the frequency range of interest, i.e. 50 - 1000 Hz. The detector will start taking data in the year 2000
Self-force Regularization in the Schwarzschild Spacetime
We discuss the gravitational self-force on a particle in a black hole
space-time. For a point particle, the full (bare) self-force diverges. The
metric perturbation induced by a particle can be divided into two parts, the
direct part (or the S part) and the tail part (or the R part), in the harmonic
gauge, and the regularized self-force is derived from the R part which is
regular and satisfies the source-free perturbed Einstein equations. But this
formulation is abstract, so when we apply to black hole-particle systems, there
are many problems to be overcome in order to derive a concrete self-force.
These problems are roughly divided into two parts. They are the problem of
regularizing the divergent self-force, i.e., ``subtraction problem'' and the
problem of the singularity in gauge transformation, i.e., ``gauge problem''. In
this paper, we discuss these problems in the Schwarzschild background and
report some recent progress.Comment: 34 pages, 2 figures, submitted to CQG, special volume for Radiation
Reaction (CAPRA7
Orbit optimization for ASTROD-GW and its time delay interferometry with two arms using CGC ephemeris
ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity using Optical
Devices] optimized for Gravitation Wave detection) is an optimization of ASTROD
to focus on the goal of detection of gravitation waves. The detection
sensitivity is shifted 52 times toward larger wavelength compared to that of
LISA. The mission orbits of the 3 spacecraft forming a nearly equilateral
triangular array are chosen to be near the Sun-Earth Lagrange points L3, L4 and
L5. The 3 spacecraft range interferometrically with one another with arm length
about 260 million kilometers. In order to attain the requisite sensitivity for
ASTROD-GW, laser frequency noise must be suppressed below the secondary noises
such as the optical path noise, acceleration noise etc. For suppressing laser
frequency noise, we need to use time delay interferometry (TDI) to match the
two different optical paths (times of travel). Since planets and other
solar-system bodies perturb the orbits of ASTROD-GW spacecraft and affect the
(TDI), we simulate the time delay numerically using CGC 2.7 ephemeris
framework. To conform to the ASTROD-GW planning, we work out a set of 20-year
optimized mission orbits of ASTROD-GW spacecraft starting at June 21, 2028, and
calculate the residual optical path differences in the first and second
generation TDI for one-detector case. In our optimized mission orbits for 20
years, changes of arm length are less than 0.0003 AU; the relative Doppler
velocities are less than 3m/s. All the second generation TDI for one-detector
case satisfies the ASTROD-GW requirement.Comment: 17 pages, 7 figures, 1 tabl