NUMERICAL-ANALYSIS OF THE FORMATION AND EVOLUTION OF GLOBAL STRINGS IN 2-DIMENSIONS(1)

We simulate the formation and the evolution of global strings taking i nto account the expansion of the universe and the concomitant change o f the effective potential, that is, the change from the restoration st age of the global U(1) symmetry to the broken stage. Starting from the thermal equilibrium state, we run simulations for 100 sets of differe nt initial conditions in 2+1 dimensions. As a result, we find deviatio n from scale invariance. This is because the energy loss mechanism is pair annihilation rather than intercommutation, so that a string and a n anti-string attract each other under a logarithmic potential.