Evolution of cosmic strings

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. 2 -.