Gravitational Radiation and Relativistic Astrophysics

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Theoretical research is being carried out in two areas related togravitational waves and their detection. The first area is theinvention of new techniques and technology for advancedlaser-interferometer gravitational-wave detectors. These advanceddetectors will entail measuring the motions of 40 kilogramsapphire-crystal mirrors with an accuracy so high that the mirrors aregoverned by the laws of quantum mechanics and not the laws of classicalphysics. The new techniques and technology entail, among other things,new configurations of mirrors and laser beams designed to deal withquantum effects that are absent in current gravitational-wavedetectors, changes in how the laser light is manipulated after itleaves the interferometer, and a reshaping of the cross sections of theinterferometer's light beams. The second area of research is thetheoretical modeling of astrophysical sources of gravitational waveswith the goal of predicting the sources' dynamical behaviors and thedetails of the waves they emit. Among the sources being modeled areoscillations of rapidly spinning, newborn neutron stars, the spins ofneutron stars that are accreting gas from companion stars (``Low-MassX-Ray Binaries''), the late, highly relativistic phase of inspiral ofblack-hole/black-hole and black-hole/neutron-star binaries, collisionsof black holes, and the tearing apart of a neutron star by a blackhole.The research on new techniques and technology for gravitational-wavedetectors is a key underpinning for the advanced detectors that arebeing proposed for construction in LIGO (the Laser InterferometerGravitational Wave Observatory) beginning in 2006, and for even moreadvanced detectors in the subsequent decade. This research makes useof, and contributes to, human knowledge in the area of quantuminformation theory --- a new, 21st century discipline that alsoincludes quantum computation. This research is likely to have muchimpact on areas of technology that---in the coming two or threedecades---will confront quantum limits on the accuracy of measurementand will try to evade them via ``quantum nondemolition'' (QND)techniques. These areas of technology include quantum optics andnanotechnology. The research on sources of gravitational waves willprovide key underpinnings for analyses of the gravitational-wave datato be produced by LIGO: It will improve the ability to findgravitational-wave signals in the noisy LIGO data, and it will providetools for extracting astrophysical information from the discoveredsignals. Thus, this research will play a key role in futuregravitational-wave-based studies of black holes, neutron stars, andtheir oscillations and collisions.