New Regime for Dense String Networks

We uncover a new transient regime that reconciles the apparent inconsistency of the Martins Shellard one scale damped string evolution model with the initial conditions predicted by the Kibble mechanism for string formation in a second order phase transition. This regime carries (in a short cosmic time $\sim .1 t_c$) the dense string network created by the Kibble {\it{mechanism}} to the (dilute) Kibble {\it{regime}} in which friction dominated strings remain till times $t_* \sim (M_P/T_c)^2 t_c$. This is possible beacause the cosmic time at the phase transition ($t_c$) is much larger than the damping time scale $l_f\sim T_c^2/T^3$. Our result has drastic implications for various non-GUT scale string mediated mechanisms.}Comment: Talk presented at COSMO99, Trieste, Sept. 26- Oct. 2, 1999. Based on work done in collaboration with Michiyasu Nagasawa and Vikram Son