Evolution of cosmic strings. II.

The evolution of a system of cosmic strings is studied following an analytic model introduced by Kibble and developed in a previous paper. The properties of a scaling solution in the radiation dominated era are studied in detail, and it is shown that the conclusions of the previous paper are not sensitive to changes in the model for loop fragmentation. The scaling solution is also compared with the numerical results of Albrecht and Turok. A crude attempt is also made to mimic transient effects in the simulations, and the implications of these transients are discussed. The bound on the string tension due to primordial nucleosynthesis is discussed in some detail. The bound at present is Gp 2 4 x 10s6. The evolution of a string system is also studied in the matter dominated era and in the transition between radiation and matter domination. The results are summarized in a pair of analytic fits that describe the evolution of the string system through the transition.