Cosmic-string evolution in flat spacetime

The numerical model of Smith and Vilenkin is used to study the evolution of cosmic strings in flat spacetime. As expected, the typical length scale of long strings, $\xi \mathrm{}\left(t\right)\mathrm{}$, grows proportionally to the evolution time, $\xi =\zeta t$, with $\zeta \sim 1$. However, the growth rate $\zeta$ depends on the lower cutoff on the loop size, indicating that physical processes on small scales have an important effect on long-string evolution. A similar conclusion follows from the analysis of the shapes of long strings. The size distribution of small loops is also inconsistent with the scaling hypothesis. It is conceivable that we failed to see the scaling behavior because of a relatively small size of the box. It is also possible that string evolution in more realistic models is scale invariant due to various dissipation processes.