Gravitational, Dilatonic and Axionic Radiative Damping of Cosmic Strings Typeset Using Revt E X 1

We study the radiation reaction on cosmic strings due to the emission of dila-tonic, gravitational and axionic waves. After discussing the renormalization of the string tension induced by time-symmetric self-interactions (thereby correcting errors in the literature), we concentrate on the nite radiation damping force associated with the half-retarded minus half-advanced \reactive" elds. We revisit a recent proposal of using a \local back reaction approximation" for the reactive elds. We nd, contrary to previous claims, that this proposal leads to antidamping in the case of the axionic eld, and to zero (integrated) damping in the case of the gravitational eld. One gets normal positive damping only in the case of the dilatonic eld. We propose to use a suitably modiied version of the local dilatonic radiation reaction as a substitute for the exact (non local) gravitational radiation reaction. The incorporation of such a local approximation to gravitational radiation reaction should allow one to complete , in a computationally non intensive way, string network simulations and to give better estimates of the amount and spectrum of gravitational radiation emitted by a cosmologically evolving network of massive strings.