Gravitational radiation from cosmic strings

Abstract

Gravitational radiation from oscillating loops of string is studied both analytically and numerically. The total radiated power is found to be P=\ensuremath{\gamma}G${\ensuremath{\mu}}^{2}$, where \ensuremath{\mu} is the mass density of the string and \ensuremath{\gamma} is a numerical coefficient \ensuremath{\sim}100. The intensity and the spectrum of the stochastic gravitational-wave background produced by the loops are calculated. Gravitational radiation from asymmetric loops carries not only energy, but also momentum; the loop recoils and accelerates like a rocket. The momentum radiation rate from loops is calculated and it is shown that cosmological loops formed with sufficiently small initial velocities are slowed down by dynamical friction and do not rocket away.