Gravitational wave experiments and early universe cosmology

Gravitational-wave experiments with interferometers and with resonant masse s can search for stochastic backgrounds of gravitational waves of cosmologi cal origin. We review both experimental and theoretical aspects of the sear ch for these backgrounds. We give a pedagogical derivation of the various r elations that characterize the response of a detector to a stochastic backg round. We discuss the sensitivities of the large interferometers under cons tructions (LIGO, VIRGO, GEO600, TAMA300, AIGO) or planned (Avdanced LIGO, L ISA) and of the presently operating resonant bars, and we give the sensitiv ities for various two-detectors correlations. We examine the existing limit s on the energy density in gravitational waves from nucleosynthesis, COBE a nd pulsars, and their effects on theoretical predictions. We discuss genera l theoretical principles for order-of-magnitude estimates of cosmological p roduction mechanisms, and then we turn to specific theoretical predictions from inflation, string cosmology, phase transitions, cosmic strings and oth er mechanisms. We finally compare with the stochastic backgrounds of astrop hysical origin. (C) 2000 Elsevier Science B.V. All rights reserved.