COSMOLOGICAL EXPANSION AND THERMODYNAMIC MECHANISMS IN COSMIC-STRING DYNAMICS

Some of the essential general principles governing cosmic string mechanics in a conformally expanding blackbody radiation background are described. It is shown that the effect of dissipative drag damping may be given a strictly conservative (i.e., variational) representation in which the usual Goto-Nambu action is simply multiplied by an appropriate cosmological temperature-dependent conformal factor. A simplified thermodynamic description is used to investigate approximately stationary equilibrium states such as may occasionally be produced as the long term outcome of large scale damping in the case of a cosmic string loop for which the (thermal or more general) distribution of surviving microscopic wiggles on an isolated cosmic string loop is characterized by a strong preponderance of ''right movers'' over ''left movers'' (or vice versa). For nonsuperconducting strings, such states can be represented very simply using the nondispersive ''warm'' cosmic string model whose dynamics is characterized by a pair of ''left'' and ''right''-moving characteristic surface currents that will be independently conserved so long as the effective heat loss to the environment is negligible. It is predicted that one of these currents will still remain conserved in the long run when account is taken of radiative energy loss from the approximately stationary equilibrium state, which will evolve with negative specific heat, monotonically increasing its effective temperature as it contracts.