Workshop on Gravitational Waves

Abstract

1. IntroductionAccording to general relativity any change in the gravitational fieldof a compact gravitating system like neutron star or black hole, willproduce a ripple on the spacetime which will propagate with the speedof light. This is a gravitational wave. Although gravitational waves havebeen predicted from the very early days of general relativity they havenot yet been detected directly. Nevertheless, their indirect influence onthe evolution of compact binary systems has been observed almost 20years ago, and the observational results agree to remarkable accuracywith the theoretical predictions.Almost thirty five years ago attempts were made to detect these tinyripples in the spacetime by constructing gravitational wave detectors inthe form of resonant bars. Today these detectors are either narrowbandresonant bars or spheres or broadband laser interferometers. The reso-nant detectors are already in operation and they have achieved sensitiv-ities close to their limits, while the laser interferometers (LIGO, VIR-GO, GEO600) are in the construction phase and expected to becomeoperational before the end of this century. The next generation of grav-itational wave detectors includes space experiments like LISA acceptedby ESA as a possible cornerstone mission.The direct detection of the gravitational waves will not only be agreat triumphforEinstein’s theory ofrelativity butisexpected to signala new era in astronomy by opening a non electromagnetic window ofobservation. By a network of at least three laser interferometers one