COSMOLOGICAL EXPANSION AND THERMODYNAMIC MECHANISMS IN COSMIC-STRING DYNAMICS

Some of the essential general principles governing cosmic string mecha nics in a conformally expanding blackbody radiation background are des cribed. It is shown that the effect of dissipative drag damping may be given a strictly conservative (i.e., variational) representation in w hich the usual Goto-Nambu action is simply multiplied by an appropriat e cosmological temperature-dependent conformal factor. A simplified th ermodynamic description is used to investigate approximately stationar y equilibrium states such as may occasionally be produced as the long term outcome of large scale damping in the case of a cosmic string loo p for which the (thermal or more general) distribution of surviving mi croscopic wiggles on an isolated cosmic string loop is characterized b y a strong preponderance of ''right movers'' over ''left movers'' (or vice versa). For nonsuperconducting strings, such states can be repres ented very simply using the nondispersive ''warm'' cosmic string model whose dynamics is characterized by a pair of ''left'' and ''right''-m oving characteristic surface currents that will be independently conse rved so long as the effective heat loss to the environment is negligib le. It is predicted that one of these currents will still remain conse rved in the long run when account is taken of radiative energy loss fr om the approximately stationary equilibrium state, which will evolve w ith negative specific heat, monotonically increasing its effective tem perature as it contracts.