Showing papers on "Gravitational wave published in 1986"

Determining the Hubble constant from gravitational wave observations

Abstract: I report here how gravitational wave observations can be used to determine the Hubble constant, H0. The nearly monochromatic gravitational waves emitted by the decaying orbit of an ultra–compact, two–neutron–star binary system just before the stars coalesce are very likely to be detected by the kilometre–sized interferometric gravitational wave antennas now being designed1–4. The signal is easily identified and contains enough information to determine the absolute distance to the binary, independently of any assumptions about the masses of the stars. Ten events out to 100 Mpc may suffice to measure the Hubble constant to 3% accuracy.

Gravitational radiation from cosmological phase transitions

Abstract: La cavitation au cours d'une transition de phase du premier ordre peut avoir donne naissance a un rayonnement gravitationnel. On propose une evaluation du spectre du fond stochastique resultant, sa variation avec les parametres qui gouvernent la transition de phase et les possibilites de son observation

Radiative gravitational fields in general relativity I. general structure of the field outside the source

Abstract: We present a well-defined formal framework, together with appropriate mathematical tools, which allow us to implement in a constructive way, and to investigate in full mathematical details, the Bonnor-Thorne approach to gravitational radiation theory. We show how to construct, within this framework, the general radiative (formal) solution of the Einstein vacuum equations, in harmonic coordinates, which is both past-stationary and past-asymptotically Minkowskian. We investigate the structure of the latter general radiative metric (including all tails and nonlinear effects) both in the near zone and in the far zone. As a side result it is proven that post-Newtonian expansions must be done by using the gauge functions (lg c)^p/c^n (p, n = positive integers).

Pulsar timing and general relativity

Abstract: Techniques are described for accounting for relativistic effects in the analysis of pulsar signals. Design features of instrumentation used to achieve millisecond accuracy in the signal measurements are discussed. The accuracy of the data permits modeling the pulsar physical characteristics from the natural glitches in the emissions. Relativistic corrections are defined for adjusting for differences between the pulsar motion in its spacetime coordinate system relative to the terrestrial coordinate system, the earth's motion, and the gravitational potentials of solar system bodies. Modifications of the model to allow for a binary pulsar system are outlined, including treatment of the system as a point mass. Finally, a quadrupole model is presented for gravitational radiation and techniques are defined for using pulsars in the search for gravitational waves.

Was Einstein Right? Putting General Relativity to the Test

Abstract: The renaissance of general relativity the straight road to curved space-time the gravitational red shift of light and clocks the departure of light from the straight and narrow the perihelion shift of Mercury - triumph or trouble the time delay of light - better late than never do the Earth and the moon fall the same the rise and fall of the Brans-Dicke theory is the gravitational constant constant the binary pulsar - gravity waves exist the frontiers of experimental relativity astronomy after the renaissance - is general relativity useful.

Eulerian and Lagrangian aspects of surface waves

Abstract: Surface waves can be recorded in two kinds of ways, either with a fixed (Eulerian) probe or with a free-floating (Lagrangian) buoy. In steep waves, the differences between corresponding properties can be very marked.By a simple physical model and by accurate calculation it is shown that the Lagrangian wave period may differ from the Eulerian wave period by as much as 38 %. The Lagrangian mean level is also higher than the Eulerian mean, leading to possible discrepancies in remote sensing of the ocean from satellites.Surface accelerations are of interest in relation to the incidence of breaking waves, and for interactions between short (gravity or capillary) waves and longer gravity waves. Eulerian accelerations tend to be very non-sinusoidal, with large downwards peaks, sometimes exceeding - g in magnitude, near to sharp wave crests. Lagrangian accelerations are much smoother; for uniform gravity waves they lie between −0.388g and +0.315g. These values are verified by laboratory experiments. In wind-generated waves the limits are probably wider.In progressive gravity waves in deep water the horizontal accelerations generally exceed the vertical accelerations. In steep waves, the subsurface accelerations can slightly exceed those at the free surface.A novel application is made to the rolling motion of ships. In very steep, irrotational waves it is shown theoretically that the flow near the wave crest can lead to the rotation of the hull through angles up to 120° by a single wave, even if the wave is not breaking. This is confirmed by simple experiments. The efficiency of the keel appears to promote capsizing.

Kinematic Resonance and Memory Effect in Free Mass Gravitational Antennas

Abstract: Detailed studies are made of two effects in the motion of free masses subject to the influence of gravitational waves: kinematic resonance and the memory effect. In the first of these, besides the oscillatory motion there is a systematic change in the distance between the bodies if they become free in an appropriate phase of the gravitational wave. The second effect takes the form that the distance between a pair of bodies will, in general, be different from the original distance after they have been influenced by a pulse of gravitational radiation. Possible practical applications of these effects in three different experimental programs are discussed. Allowance for these effects should lessen the requirements on the detection systems and ultimately raise the sensitivity of gravitational antennas.

Symmetry classes of pp-waves.

Abstract: The isometry groups admitted by plane-fronted gravitational waves with parallel rays are determined without use of any field equations. New groups with 5, 6, and 7 parameters arise which cannot occur for (nontrivial) exact solutions of Einstein's vacuum field equations. For all 17 possible cases the functional form of the free function in the metric is given. We apply the classification to Einstein-Maxwell fields and also determine, in Riemann-Cartan geometry, the form of the torsion tensor by assuming the vanishing of its Lie derivative with respect to the generators of the isometry groups.

New millisecond pulsar in a binary system

Abstract: Recent observations1,2 at the Arecibo Observatory have resulted in the discovery of PSR1855+09, a pulsar with period P=5.362 ms, moving in a nearly circular orbit of period 12.3 days. The pulsar is only the third one known with P < 10 ms, and the sixth known radio pulsar in a binary system. (Discovery of a seventh binary pulsar is announced in an accompanying paper3.) Three of the seven binaries are among the fastest five of more than 400 pulsars—a fact that provides strong support for the conclusion that fast pulsars are ‘recycled’ neutron stars, spun up during a phase of mass accretion from an evolving companion star. The pulsar has a small dispersion measure (13.3 cm−3 pc), suggesting a distance of only ∼350 pc. The proximity of this pulsar and its location within 25 pc of the galactic plane argue that millisecond pulsars form a significant fraction (∼10%) of the pulsar population, leaving many detectable ones undiscovered4,5. Its signal is strong enough to permit pulse-arrival-time measurements with single-day uncertainties of <3µs. Timing observations already suggest that PSR1855+09, like the 1.5-ms pulsar PS R1937+21, will prove to be a natural clock of extremely high stability6. The existence of a second pulsar with extremely small timing uncertainties will greatly aid the search for background gravitational waves using millisecond pulsars as detectors.

Cylindrical waves in general relativity

Abstract: A convenient framework is set up for constructing cylindrically symmetric solutions of the Einstein and the Einstein-Maxwell equations, and it is shown how a Hamiltonian density can be defined for space-times with cylindrical symmetry. Solutions are obtained that represent stationary monochromatic waves and satisfy all the requisite conditions of regularity. The case when the gravitational field is coupled with a perfect fluid in which the energy density is equal to the pressure is also briefly considered.

Theory and Experiment in Gravitational Physics

Abstract: Clifford M Will 1985 Cambridge: Cambridge University Press ix + 342 pp price £15 (paperback) ISBN 0 521 31710 X Researchers entering the general area of gravitation and cosmology for the first time may be forgiven for believing that general relativity is the only viable theory of gravity, as so little is usually discussed in the literature concerning alternative theories. In fact, up until 1960, the experimental evidence for general relativity was meagre in the extreme.

Gravitational Collapse and Relativity

Abstract: The XIV Yamada Conference on GRAVITATIONAL COLLAPSE and RELATIVITY was held at the Kyoto International Conference Hall, Kyoto, Japan, from April 7 through April 11, 1986. The Conference was attended by 72 relativists and astrophysicists from 13 countries. The aim of the Conference was to survey the theoretical developments of the study of gravitational collapse and black holes in the framework of general relativity. Main emphasis was put on ''Numerical relativity,'' ''Exact solution'' and related problems in classical relativity. However new aspects of black holes in quantum effects and higher-dimensional theory were also discussed. The record of three discourses given by K. Thorne, S. Hayakawa and R. Penrose is also contained in this volume. This session was opened also to the non-participants of the conference. There have been many rather quiet progresses in this field during the last several years. The impression through the discussions at the Conference is that these progresses in theoretical study may have in near future more contact with observational activities such as detection of gravitational waves and astrophysical black holes.

Cylindrical waves and cosmic strings of Petrov type D.

Abstract: A three-parameter family of (time-dependent) cylindrically symmetric solutions of the vacuum Einstein equations is obtained. They all are asymptotically flat, they admit a regular axis, and they are free from curvature singularities. For general values of the parameters the solution exhibits an angle deficit in going around the axis and it is interpreted as a cosmic string surrounded by gravitational waves. The angle deficit is eliminated for a two-parameter subfamily, leading to an everywhere-regular Petrov type-D spacetime describing the propagation of nonradiating cylindrical gravitational waves. A relationship between the linear mass density of the string and the C-energy of the spacetime is established.

SQUIDs, Brains and Gravity Waves

Abstract: ▸ A lonely instrument in Baja California records tiny fluctuations in the Earth's magnetic field, giving valuable information on the location of geothermal energy.▸ An extremely quiet amplifier detects electrical noise generated by the fluctuating spins in a collection of chlorine nuclei—the first observation of nuclear‐spin noise.▸ Superconducting gradiometers in liquid helium measure tiny fluctuating magnetic fields emanating from the human brain (see figure 1), pinpointing the source of the electrical discharge associated with focal epilepsy.▸ An aluminum bar weighing 4800 kg and cooled to 4.2 K rests in a vacuum chamber at Stanford University, working as the world's most sensitive monitor of gravitational radiation.

Postthermonuclear Runaway Angular Momentum Loss in Cataclysmic Binaries

Abstract: Durant les phases d'enveloppe commune suivant les flashes d'hydrogene dans la composante naine blanche de binaires cataclysmiques, le moment angulaire et l'energie peuvent etre transferres de l'orbite vers l'enveloppe commune par des processus de friction

Possible anisotropic phases in the early universe and gravitational wave background

Abstract: We discuss possible anisotropic and inhomogeneous phases in the early Universe at relatively late epochs corresponding to the temperatures 1 GeV–10 TeV. The anisotropy and inhomogeneity of the energy-momentum tensor at the horizon scale gives rise to the generation of a stochastic gravitational wave background. It is shown that the present amplitudes and frequencies of this background may be well within the access of planned gravitational wave detectors.

Propagation of gravitational waves through pressureless matter.

Abstract: The authors investigate the propagation of small-amplitude gravitational waves through pressureless matter ('dust'). After establishing the local linearisation stability of Einstein's equation for dust about any of its solutions they use the WKB method to study the locally plane, linearised perturbations of an arbitrary background dust spacetime asymptotically for small wavelengths. The dispersion relation exhibits two modes. One is simply degenerate and represents gravitational waves, whereas the other is doubly degenerate and describes density and vorticity perturbations. The waves are shown to propagate along the null geodesics of the background; in leading WKB order their amplitudes behave as in vacuo. The rays associated with the matter mode are the wordlines of the background dust. In leading order the perturbations of density and 4-velocity vanish for both modes.

Parametric Transducer for Gravitational Radiation Detector

Abstract: A low-noise parametric vibration transducer using a pair of superconducting microwave cavities has been developed for use with cryogenic gravitational radiation antennas. Pumped by a 9.7-GHz SCSO, the cavities convert mechanical vibration into microwave sidebands which, after demodulation, reproduce the low-frequency signal. For the performance test of the transducer system, the cavities were mounted on a 15-kHz prototype disk antenna at 4.2 K. A transducer noise temperature of 23 mK was obtained at the antenna frequency, and hence a quantum noise number of 3.4×104.

On the collision of impulsive gravitational waves when coupled with null dust

Abstract: The problem of colliding impulsive gravitational waves is considered when the region of space-time, after the instant of collision, is filled with a mixture of null dusts moving in opposite directions. The extension of the resulting space-time, to regions before the instant of collision, shows that null dust follows the leading edges of the impulsive waves, and, further, that one can arrange that the space-time in these regions is identical with what prevails when a perfect fluid with є = p fills the region after the instant of collision. This ambiguity in the space-time, after the instant of collision, must be traced to an inherent ambiguity in the nature of null dust and its relation with a perfect fluid with є = p .

Gravitational solitons and spatial flatness

Abstract: Reduction of initial spatial curvature by gravi-solitons is studied in the framework of composite universe. These models have asymptotic regions with different homogeneity groups matched by the gravitational pulses. They admit only initial singularities and ultimately evolve into the Bianchi type I regime.

Cylindrical gravitational waves with two degrees of freedom: An exact solution

Abstract: The exact two-parameter solution of Einstein's equations described below represents ingoing and outgoing cylindrical gravitational waves with two degrees of polarization. It has been obtained from the Kerr metric by applying a well-known trick but, unlike the Kerr metric, it has no singularities.