International conference on gravitational waves: Sources and Detectors

Valeria Ferrari and Maria Alessandra Papa, Università di Roma

The Conference was held on March 19-23 1996 in Cascina (Pisa) near the site where the VIRGO interferometer is now under construction. It was attended by 120 physicists plus a sociologist who is ``keeping under observation" the scientific community involved in the search of gravitational waves. The aim of the Conference was to gather the efforts of the theoreticians and the experimentalists working in the field and stimulate future work on the phenomenology of GWs in close connection with the experiments.

On the theoretical side, the sources of GWs have been the subject of several talks. Inspiralling compact binaries have been discussed by L. Blanchet, who showed that, in order to extract significant information from VIRGO and LIGO observations, the radiation field and the internal dynamics of the binary system must be evaluated including post-newtonian corrections at least up to third order. E. Gorgoulhon and S. Bonazzola have discussed how efficiently a magnetic dipole moment of a rotating neutron star can induce distortions in the axial symmetry with consequent emission of GWs. Other mechanisms which may be responsible for axial symmetry breaking (such us Chandrasekhar-Friedman-Schutz instability, MacLaurin-Jacobi transition and crust defects) have also been reviewed. K. Kokkotas has shown that from the detailed knowledge of the spectrum of the quasi-normal modes of a compact star one can infer the values of its mass and radius and have indications on its internal structure. Great interest have received the estimates of the relic stochastic GW background spectrum provided by inflationary cosmology in the framework of string theory, which have been presented by G.Veneziano and R. Brustein. They suggest that, depending on the constraints of the theory, the predicted power spectra may be detectable. Another kind of stochastic GW background due to cosmological supernovae explosion, has been evaluated (D. Blair and A. Di Fazio-V.Ferrari ), and it emerges that it may be competitive with the string background in the VIRGO-LIGO bandwidth.

Fully relativistic numerical codes for gravitational collapse and coalescing compact objects have been shown to be in progress.

The status of the experiments was discussed both in plenary talks and workshops. A number of resonant bars are actually taking data as well as the TENKO-100 interferometer in Japan. The quoted sensitivities to a pulse of GWs for the resonant experiments are:

EXPLORER (Geneva, Cern)
NAUTILUS (Frascati LNF, Roma),
NIOBE (Perth, UWA) ,
TENKO-100 (ISAS Japan) and .
AURIGA (Legnaro LNL, Padova) started the cryogenic tests and will soon be operational.

The state of the art for the interferometric antennas, VIRGO, LIGO, GEO600, and TAMA, has been reported and the following expected sensitivities have been quoted:

VIRGO: and
LIGO: in a bandwidth of
GEO600: (depending on bandwidth)
TAMA: in a bandwidth of

Doppler tracking experiments and upper limits on the emission of GWs in the range of have been reviewed by Luciano Iess. The sensitivity of LISA to GWs from various binary systems (WD-WD, BH-BH, WD-BH, MBH-MBH etc) and to GWs of cosmological origin, has been discussed, together with the planning of the experiment, by Peter Bender. From his graphs LISA's sensitivity should range between and

Data analysis for extracting GW-signals from present and future data, has focused essentially on the study of filtering procedures for single detectors and for different kinds of networks. These two issues have been discussed in talks regarding the use of APE1000 to detect coalescing binaries and pulsars parameters (A.Vicere'), the search of monocromatic and stochastic GWs with NAUTILUS and EXPLORER (P.Astone), the estimate of chirp parameters (I.M.Pinto), the signal deconvolution for a multimode spherical detector (E.Coccia), the cross-correlation of data from several bars (S. Vitale), the use of bar-interferometer networks for pulse detection (B. Schutz), and the use of local arrays of small resonators for high frequency detection (S.Frasca).

Jorge Pullin
Sun Sep 1 16:45:26 EDT 1996