CONSTRAINTS ON THE GRAVITY-WAVE BACKGROUND GENERATED BY COSMIC STRINGS

We investigate the limits that can be placed on a cosmic-string-generated stochastic gravity-wave background by timing of the millisecond pulsar and by primordial nucleosynthesis. These limits on the gravity-wave background are used to generate limits on the mass per unit length of the cosmic string, mu. The limit due to the millisecond-pulsar constraint is mu < 4 x 10(-5)c2/G while the nucleosynthesis limit ranges from mu < 6 x 10(-6)c2/G to mu < 2 x 10(-5)c2/G depending on the history of the Universe at temperatures above 1 TeV and the details of the QCD phase transition. These limits are significantly weaker than the best limit obtained from observations of the microwave background (mu < 5 x 10(-6)c2/G) and are well above the value of mu that seems to be favored by the string-seeded galaxy-formation scenario.