Optical bars in gravitational wave antennas

A new scheme of gravitational wave antennas is proposed which due to the effect of light pressure behaves analogous to solid state antenna of the same scale. The gravitational signal in this scheme is transformed into the force acting on a mirror. The resulting mirror displacement may be detected using methods standard for the bar antennas. The scheme provides gain in resolution and allows one to beat the standard quantum limit without the use of non-classical pumping.     

Antenna pattern for four gravitational wave antennas

Summary The antenna pattern is analysed for four widely spaced cryogenic gravitational wave antennas which are expected to begin operating in coincidence during 1987. Using reasonable assumptions for senstivity, the four-antenna pattern is shown to give between 50% and 80% sky coverage for circularly polarized radiation under the minimum-detection criterion of two-way coincidence. One-hundred percent sky coverage can be achieved if one antenna is reoriented, but this is at the expense of reduced probability for 3-way coincidences.     

Coherent addition of laser oscillators for use in gravitational wave antennas

The amount of laser power required for the large scale interferometric gravitational wave antennas currently being proposed may well require the coherent summation of the light from several lasers. In this paper the feasibility of two potential summation schemes are experimentally compared and contrasted by adding the outputs of two argon lasers.     

Optimal interconnection of resonant gravitational antennas

A new scheme for interconnecting resonant gravitational antennas is considered. This algorithm is based on the theory of combined detection and estimation of a vectorial signal on a pseudo-gravitational impulse background. The used minimax approach takes into account the beats between gravitational and pseudo-gravitational signals.     

Localized single-photon wave functions in free space

We solve the joint open problems of photon localization and single-photon wave functions in the context of spontaneous emission from an excited atom in free space. Our wave functions are well-defined members of a discrete orthonormal function set. Both the degree and shape of the localization are controlled by entanglement mapping onto the atom wave function, even though the atom is remote from the photon.     

Stochastic gravitational wave background due to gravitational wave memory

Gravitational wave memory is an important prediction of general relativity, which has not been detected yet. Amounts of memory events can form a stochastic gravitational wave memory background. Here we find that memory background can be described as a Brownian motion in the condition that the observation time is longer than the averaged time interval between two successive memory events. We investigate, for the first time, the memory background of binary black hole coalescences. We only consider...     

Probing for new physics and detecting non-linear vacuum QED effects using gravitational wave interferometer antennas

Low energy non-linear QED effects in vacuum have been predicted since 1936 and have been subject of research for many decades. Two main schemes have been proposed for such a ‘first’ detection: measurements of ellipticity acquired by a linearly polarized beam of light passing through a magnetic field and direct light–light scattering. The study of the propagation of light through an external field can also be used to probe for new physics such as the existence of axion-like particles and millicharged particles. Their existence in nature would cause the index of refraction of vacuum to be different from unity in the presence of an external field and dependent of the polarization direction of the propagating light. The major achievement of reaching the project sensitivities in gravitational wave interferometers such as LIGO and VIRGO has opened the possibility of using such instruments for the detection of QED corrections in electrodynamics and for probing new physics at very low energies. We show that it is possible to distinguish between various scenarios of new physics in the hypothetical case of detecting unexpected values. Considering the design sensitivity in the strain of the near future VIRGO+ interferometer leads to a variable dipole magnet configuration such that B ² D≥13000 T² m  for a ‘first’ vacuum non-linear QED detection.     

Quantum limitations on the sensitivity of gravitational wave detectors with free masses

The problem of recording a classical disturbance by tracking the coordinate of a free particle is examined within the scope of nonrelativistic quantum mechanics. The absence of the fundamental limitation on the sensitivity — the standard quantum limit — is proven. An arbitrarily small disturbance can be recorded with preparation of the system in a quantum state having a negative quantum correlation coefficient between the observable coordinate and momentum. It is shown that it belongs to the collective coherent states — the condensed states. Arguments are presented for the absence of fundamental quantum limits on the magnitude of the recordable disturbance in the measurement of an arbitrary observable with a continuous spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 14–19, September, 1988.The author thanks A. A. Grib for useful discussions and interest in the work.     

Quantum speed meter in laser gravitational antennas

A method of enhancing the sensitivity of laser gravitational antennas based on tracking of the velocity of the antenna reflectors instead of conventional tracking of their displacement is considered. This method allows one to overcome the standard quantum detection limit for a weak force. An optical scheme of a gravitational wave detector on the basis of a speed meter is considered. The formulas for the limiting sensitivity of the given scheme taking optical losses into account are obtained. The possibility of realizing the considered measurement method in presently existing laser gravitational antennas is analyzed.     

High-energy gravitational antennas: A theoretical approach

Summary Devices exploiting nuclear resonances are believed to be very promising in detecting weak gravitational-wave perturbations. The main difficulty with these systems is that the high-energy photons which induce the nuclear transitions need to travel over distances comparable with the gravity wave wave-lengths (∼100 km) in order to lead to the absorption the largest frequency shift, due to gravitational radiation. Here we show that, if these high-energy photons are not produced by nuclear de-excitation, but by inverse Compton scattering of laser light with ultrarelativistic electrons, a deviation from the resonant frequencies of the order of the gravity wave amplitude is still attained without the photon travel time being comparable with the gravitational-wave periods.

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Riassunto L'uso di apparati che sfruttano i processi di risonanza nucleare sembra essere promettente nella rivelazione delle onde gravitazionali. La difficoltà maggiore in questi apparati è che i fotoni di alta energia che inducono le risonanze devono viaggiare per distanze confrontabili con la lunghezza d'onda delle onde gravitazionali (∼100 km) per poter risentire della variazione di frequenza massima dovuta all'interazione con le onde gravitazionali. Qui si mostra che se questi fotoni di alta energia sono prodotti non dalla diseccitazione nucleare ma da urti Compton inverso di laser con particelle relativistiche, una deviazione dalla frequenza di risonanza dell'ordine dell'ampiezza delle onde gravitazionali è ottenuta senza che il tempo di volo dei fotoni sia confrontabile con il periodo delle onde gravitazionali stesse.

     

Space-borne gravitational wave observatories

An overview of our current knowledge of black seed formation models following their growth history over cosmic time is presented. Both light seed formation channels remnants of the first stars and the more massive direct collapse seed formation scenarios are outlined. In particular, the focus is on the implications of these various scenarios and what these initial conditions imply for the highest redshift black holes, the local black hole population, the highest mass black holes at each epoch and the low mass end of the black hole mass function all of which are currently observed. The goal is to present a broad and comprehensive picture of the current status; the open questions and challenges faced by black hole growth models in matching current observational data and the prospects for future observations that will help discriminate between competing models.     

On the response of gravitational antennas to dilatonic waves

It is pointed out that the coupling of macroscopic test masses to the gravi-dilaton background of string theory is non geodesic, in general, and cannot be parametrized by a Brans–Dicke model of scalar-tensor gravity. The response of gravitational antennas to dilatonic waves should be analyzed through a generalized equation of geodesic deviation, taking into account the possible direct coupling of the background to the (composition-dependent) dilatonic charge of the antenna.     

Calculation of the Peierls-Yoccoz translational mass for Hartree-Fock wave functions

The Peierls-Yoccoz projection method for translation is applied to Hartree-Fock wave functions constructed on a mesh for ${}^4\text{He}$ and ${}^{16}\text{O}$. As expected, the mass parameters differ from the nuclear masses, indicating a breaking of galilean invariance.     

Comparison of parametric instabilities for different test mass materials in advanced gravitational wave interferometers

Following the recognition that parametric instabilities can significantly compromise the performance of advanced laser interferometer gravitational wave detectors, we compare the performance of three different test mass configurations: all fused silica test masses, all sapphire test masses and fused silica inboard test masses with sapphire end test masses. We show that the configuration with sapphire end test masses offers the opportunity for thermal tuning on a time scale comparable to the ring up time of oscillatory instabilities. This approach may enable significant reduction of parametric gain.     

Underground spherical gravitational wave detector

Recently significant advancements have been made towards the realization of a large spherical gravitational wave detector. Research and development activities have already begun in several countries. We present here the main features and capabilities of a spherical gravitational wave detector. In particular, we discuss the interaction between a spherical antenna and cosmic rays that may require a large detector to be placed underground.