45 research outputs found
Testing Lorentz Invariance with a Double-Pass Optical Ring Cavity
We have developed an apparatus to test Lorentz invariance in the photon
sector by measuring the resonant frequency difference between two
counterpropagating directions of an asymmetric optical ring cavity using a
double-pass configuration. No significant evidence for the violation was found
at the level of . Details of our apparatus and
recent results are presented.Comment: 4 pages, 1 figure. Presented at the Sixth Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 17-21, 201
A theoretical approach to thermal noise caused by an inhomogeneously distributed loss -- Physical insight by the advanced modal expansion
We modified the modal expansion, which is the traditional method used to
calculate thermal noise. This advanced modal expansion provides physical
insight about the discrepancy between the actual thermal noise caused by
inhomogeneously distributed loss and the traditional modal expansion. This
discrepancy comes from correlations between the thermal fluctuations of the
resonant modes. The thermal noise spectra estimated by the advanced modal
expansion are consistent with the results of measurements of thermal
fluctuations caused by inhomogeneous losses.Comment: 10 pages, 4 figure
Upper Limit on Gravitational Wave Backgrounds at 0.2 Hz with Torsion-bar Antenna
We present the first upper limit on gravitational wave (GW) backgrounds at an
unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was
proposed to search for low-frequency GWs. We have developed a small-scaled TOBA
and successfully found {\Omega}gw(f) < 4.3 \times 1017 at 0.2 Hz as
demonstration of the TOBA's capabilities, where {\Omega}gw (f) is the GW energy
density per logarithmic frequency interval in units of the closure density. Our
result is the first nonintegrated limit to bridge the gap between the LIGO band
(around 100 Hz) and the Cassini band (10-6 - 10-4 Hz).Comment: 4 pages, 5 figure
Systematic measurement of the intrinsic losses in various kinds of bulk fused silica
We systematically measured and compared the mechanical losses of various
kinds of bulk fused silica. Their quality factors ranged widely from 7x10^5 to
4x10^7, the latter being one of the highest reported among bulk fused silica.
We observed frequency-dependent losses and a decrease in the losses upon
annealing.Comment: 14 pages, 4 figures, Submitted to Phys. Lett.
Current status of Japanese detectors
Current status of TAMA and CLIO detectors in Japan is reported in this
article. These two interferometric gravitational-wave detectors are being
developed for the large cryogenic gravitational wave telescope (LCGT) which is
a future plan for detecting gravitational wave signals at least once per year.
TAMA300 is being upgraded to improve the sensitivity in low frequency region
after the last observation experiment in 2004. To reduce the seismic noises, we
are installing new seismic isolation system, which is called TAMA Seismic
Attenuation System, for the four test masses. We confirmed stable mass locks of
a cavity and improvements of length and angular fluctuations by using two SASs.
We are currently optimizing the performance of the third and fourth SASs. We
continue TAMA300 operation and R&D studies for LCGT. Next data taking in the
summer of 2007 is planned.
CLIO is a 100-m baseline length prototype detector for LCGT to investigate
interferometer performance in cryogenic condition. The key features of CLIO are
that it locates Kamioka underground site for low seismic noise level, and
adopts cryogenic Sapphire mirrors for low thermal noise level. The first
operation of the cryogenic interferometer was successfully demonstrated in
February of 2006. Current sensitivity at room temperature is close to the
target sensitivity within a factor of 4. Several observation experiments at
room temperature have been done. Once the displacement noise reaches at thermal
noise level of room temperature, its improvement by cooling test mass mirrors
should be demonstrated.Comment: 6 pages, 5 figures, Proceedings of GWDAW-1
Coincidence analysis to search for inspiraling compact binaries using TAMA300 and LISM data
Japanese laser interferometric gravitational wave detectors, TAMA300 and
LISM, performed a coincident observation during 2001. We perform a coincidence
analysis to search for inspiraling compact binaries. The length of data used
for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors
are operated simultaneously. TAMA300 and LISM data are analyzed by matched
filtering, and candidates for gravitational wave events are obtained. If there
is a true gravitational wave signal, it should appear in both data of detectors
with consistent waveforms characterized by masses of stars, amplitude of the
signal, the coalescence time and so on. We introduce a set of coincidence
conditions of the parameters, and search for coincident events. This procedure
reduces the number of fake events considerably, by a factor
compared with the number of fake events in single detector analysis. We find
that the number of events after imposing the coincidence conditions is
consistent with the number of accidental coincidences produced purely by noise.
We thus find no evidence of gravitational wave signals. We obtain an upper
limit of 0.046 /hours (CL ) to the Galactic event rate within 1kpc from
the Earth. The method used in this paper can be applied straightforwardly to
the case of coincidence observations with more than two detectors with
arbitrary arm directions.Comment: 28 pages, 17 figures, Replaced with the version to be published in
Physical Review
Results of the search for inspiraling compact star binaries from TAMA300's observation in 2000-2004
We analyze the data of TAMA300 detector to search for gravitational waves
from inspiraling compact star binaries with masses of the component stars in
the range 1-3Msolar. In this analysis, 2705 hours of data, taken during the
years 2000-2004, are used for the event search. We combine the results of
different observation runs, and obtained a single upper limit on the rate of
the coalescence of compact binaries in our Galaxy of 20 per year at a 90%
confidence level. In this upper limit, the effect of various systematic errors
such like the uncertainty of the background estimation and the calibration of
the detector's sensitivity are included.Comment: 8 pages, 4 Postscript figures, uses revtex4.sty The author list was
correcte
The Japanese space gravitational wave antenna; DECIGO
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future
Japanese space gravitational wave antenna. DECIGO is expected to open a new window of
observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing
various mysteries of the universe such as dark energy, formation mechanism of supermassive
black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of
three drag-free spacecraft, whose relative displacements are measured by a differential Fabry–
Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre-
DECIGO first and finally DECIGO in 2024