Cosmic string loop shapes
  We analyze the shapes of cosmic string loops found in large-scale simulations
of an expanding-universe string network. The simulation does not include
gravitational back reaction, but we model that process by smoothing the loop
using Lorentzian convolution. We find that loops at formation consist of
generally straight segments separated by kinks. We do not see cusps or any
cusp-like structure at the scale of the entire loop, although we do see very
small regions of string that move with large Lorentz boosts. However, smoothing
of the string almost always introduces two cusps on each loop. The smoothing
process does not lead to any significant fragmentation of loops that were in
non-self-intersecting trajectories before smoothing.
