RADIATION OF NAMBU-GOLDSTONE BOSONS FROM INFINITELY LONG COSMIC STRINGS

Nambu-Goldstone-boson radiation from an infinitely long string with a helicoidal standing wave is studied in the weak-field approximation. The radiation power and the spectrum are calculated. In the case of a single-small-amplitude helicoidal standing wave, the radiated power goes as epsilon-10, indicating that the Nambu-Goldstone-boson radiation mechanism is efficient only for large-amplitude waves. A simple analysis of the radiation due to a wide spectrum of small-amplitude waves indicate that in general the emitted power goes as epsilon-4.