Runaway cosmic strings

Two effects of cosmic strings are examined in connection with the picture of string-induced galaxy formation. First, loops of cosmic string behave like relativistic gyroscopes, and undergo only a very slow precession under the influence of newtonian gravitational torques. They thus impose a 'stiff' time-averaged quadrupolar gravitational potential on matter in their vicinity. Second, the gravitational radiation beamed by an oscillating loop probably has a significant component of dipole asymmetry when averaged over the loop decay time. Recoil reaction on the loop causes a coherent acceleration over time and eventually leads to a high peculiar velocity when loops decay. String loops today would then not generally be found in the centres of galaxies and clusters, but flying freely through intergalactic space. (author)