1,566 research outputs found
Optical noise correlations and beating the standard quantum limit in advanced gravitational-wave detectors
The uncertainty principle, applied naively to the test masses of a
laser-interferometer gravitational-wave detector, produces a Standard Quantum
Limit (SQL) on the interferometer's sensitivity. It has long been thought that
beating this SQL would require a radical redesign of interferometers. However,
we show that LIGO-II interferometers, currently planned for 2006, can beat the
SQL by as much as a factor two over a bandwidth \Delta f \sim f, if their
thermal noise can be pushed low enough. This is due to dynamical correlations
between photon shot noise and radiation-pressure noise, produced by the LIGO-II
signal-recycling mirror.Comment: 12 pages, 2 figures; minor changes, some references adde
Sources of Gravitational Waves: Theory and Observations
Gravitational-wave astronomy will soon become a new tool for observing the Universe. Detecting and interpreting gravitational waves will require deep theoretical insights into astronomical sources. The past three decades have seen remarkable progress in analytical and numerical computations of the source dynamics, development of search algorithms and analysis of data from detectors with unprecedented sensitivity. This Chapter is devoted to examine the advances and future challenges in understanding the dynamics of binary and isolated compact-object systems, expected cosmological sources, their amplitudes and rates, and highlights of results from gravitational-wave observations. All of this is a testament to the readiness of the community to open a new window for observing the cosmos, a century after gravitational waves were first predicted by Albert Einstein
The two-phase issue in the O(n) non-linear -model: A Monte Carlo study
We have performed a high statistics Monte Carlo simulation to investigate
whether the two-dimensional O(n) non-linear sigma models are asymptotically
free or they show a Kosterlitz- Thouless-like phase transition. We have
calculated the mass gap and the magnetic susceptibility in the O(8) model with
standard action and the O(3) model with Symanzik action. Our results for O(8)
support the asymptotic freedom scenario.Comment: 3 pgs. espcrc2.sty included. Talk presented at LATTICE96(other
models
Gravitational waves from inspiraling binary black holes
Binary black holes are the most promising candidate sources for the first
generation of earth-based interferometric gravitational-wave detectors. We
summarize and discuss the state-of-the-art analytic techniques developed during
the last years to better describe the late dynamical evolution of binary black
holes of comparable masses.Comment: References added and updated; few typos correcte
Laser-interferometer gravitational-wave optical-spring detectors
Using a quantum mechanical approach, we show that in a gravitational-wave
interferometer composed of arm cavities and a signal recycling cavity, e.g.,
the LIGO-II configuration, the radiation-pressure force acting on the mirrors
not only disturbs the motion of the free masses randomly due to quantum
fluctuations, but also and more fundamentally, makes them respond to forces as
though they were connected to an (optical) spring with a specific rigidity.
This oscillatory response gives rise to a much richer dynamics than previously
known, which enhances the possibilities for reshaping the LIGO-II's noise
curves. However, the optical-mechanical system is dynamically unstable and an
appropriate control system must be introduced to quench the instability.Comment: 7 pages, 3 figures; to appear in the Proceedings of 4th Edoardo
Amaldi Conference on Gravitational Waves, Perth, Australia, 8-13 July 200
Transition from inspiral to plunge in precessing binaries of spinning black holes
We investigate the non-adiabatic dynamics of spinning black hole binaries by
using an analytical Hamiltonian completed with a radiation-reaction force,
containing spin couplings, which matches the known rates of energy and angular
momentum losses on quasi-circular orbits. We consider both a straightforward
post-Newtonian-expanded Hamiltonian (including spin-dependent terms), and a
version of the resummed post-Newtonian Hamiltonian defined by the Effective
One-Body approach. We focus on the influence of spin terms onto the dynamics
and waveforms. We evaluate the energy and angular momentum released during the
final stage of inspiral and plunge. For an equal-mass binary the energy
released between 40Hz and the frequency beyond which our analytical treatment
becomes unreliable is found to be, when using the more reliable Effective
One-Body dynamics: 0.6% M for anti-aligned maximally spinning black holes, 5% M
for aligned maximally spinning black hole, and 1.8% M for non-spinning
configurations. In confirmation of previous results, we find that, for all
binaries considered, the dimensionless rotation parameter J/E^2 is always
smaller than unity at the end of the inspiral, so that a Kerr black hole can
form right after the inspiral phase. By matching a quasi-normal mode ringdown
to the last reliable stages of the plunge, we construct complete waveforms
approximately describing the gravitational wave signal emitted by the entire
process of coalescence of precessing binaries of spinning black holes.Comment: 31 pages, 7 tables, and 13 figure
Quantum noise in laser-interferometer gravitational-wave detectors with a heterodyne readout scheme
We analyze and discuss the quantum noise in signal-recycled laser
interferometer gravitational-wave detectors, such as Advanced LIGO, using a
heterodyne readout scheme and taking into account the optomechanical dynamics.
Contrary to homodyne detection, a heterodyne readout scheme can simultaneously
measure more than one quadrature of the output field, providing an additional
way of optimizing the interferometer sensitivity, but at the price of
additional noise. Our analysis provides the framework needed to evaluate
whether a homodyne or heterodyne readout scheme is more optimal for second
generation interferometers from an astrophysical point of view. As a more
theoretical outcome of our analysis, we show that as a consequence of the
Heisenberg uncertainty principle the heterodyne scheme cannot convert
conventional interferometers into (broadband) quantum non-demolition
interferometers.Comment: 16 pages, 8 figure
Sagnac Interferometer as a Speed-Meter-Type, Quantum-Nondemolition Gravitational-Wave Detector
According to quantum measurement theory, "speed meters" -- devices that
measure the momentum, or speed, of free test masses -- are immune to the
standard quantum limit (SQL). It is shown that a Sagnac-interferometer
gravitational-wave detector is a speed meter and therefore in principle it can
beat the SQL by large amounts over a wide band of frequencies. It is shown,
further, that, when one ignores optical losses, a signal-recycled Sagnac
interferometer with Fabry-Perot arm cavities has precisely the same
performance, for the same circulating light power, as the Michelson speed-meter
interferometer recently invented and studied by P. Purdue and the author. The
influence of optical losses is not studied, but it is plausible that they be
fairly unimportant for the Sagnac, as for other speed meters. With squeezed
vacuum (squeeze factor ) injected into its dark port, the
recycled Sagnac can beat the SQL by a factor over the
frequency band 10 {\rm Hz} \alt f \alt 150 {\rm Hz} using the same
circulating power kW as is used by the (quantum limited)
second-generation Advanced LIGO interferometers -- if other noise sources are
made sufficiently small. It is concluded that the Sagnac optical configuration,
with signal recycling and squeezed-vacuum injection, is an attractive candidate
for third-generation interferometric gravitational-wave detectors (LIGO-III and
EURO).Comment: 12 pages, 6 figure
Binary black hole coalescence in the large-mass-ratio limit: the hyperboloidal layer method and waveforms at null infinity
We compute and analyze the gravitational waveform emitted to future null
infinity by a system of two black holes in the large mass ratio limit. We
consider the transition from the quasi-adiabatic inspiral to plunge, merger,
and ringdown. The relative dynamics is driven by a leading order in the mass
ratio, 5PN-resummed, effective-one-body (EOB), analytic radiation reaction. To
compute the waveforms we solve the Regge-Wheeler-Zerilli equations in the
time-domain on a spacelike foliation which coincides with the standard
Schwarzschild foliation in the region including the motion of the small black
hole, and is globally hyperboloidal, allowing us to include future null
infinity in the computational domain by compactification. This method is called
the hyperboloidal layer method, and is discussed here for the first time in a
study of the gravitational radiation emitted by black hole binaries. We
consider binaries characterized by five mass ratios, ,
that are primary targets of space-based or third-generation gravitational wave
detectors. We show significative phase differences between finite-radius and
null-infinity waveforms. We test, in our context, the reliability of the
extrapolation procedure routinely applied to numerical relativity waveforms. We
present an updated calculation of the gravitational recoil imparted to the
merger remnant by the gravitational wave emission. As a self consistency test
of the method, we show an excellent fractional agreement (even during the
plunge) between the 5PN EOB-resummed mechanical angular momentum loss and the
gravitational wave angular momentum flux computed at null infinity. New results
concerning the radiation emitted from unstable circular orbits are also
presented.Comment: 22 pages, 18 figures. Typos corrected. To appear in Phys. Rev.
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