Quantitative string evolution

An analytic model of long string network evolution, recently developed by the authors, is presented in detail, and modified to describe string loop evolution. By treating the average string velocity, as well as the characteristic length scale, as dynamical variables, one can include the effects of frictional forces on the evolution of the network. This generalized ''one-scale'' model provides a quantitative picture of the complete evolution of a string network, including the prediction of previously unknown transient scaling regimes and a detailed analysis of the evolution of the loop population. The evolution of all cosmologically interesting string networks is studied in detail, and possible consequences of our results are discussed.