String networks in Z_N Lotka-Volterra competition models
  In this letter we give specific examples of Z_N Lotka-Volterra competition
models leading to the formation of string networks. We show that, in order to
promote coexistence, the species may arrange themselves around regions with a
high number density of empty sites generated by predator-prey interactions
between competing species. These configurations extend into the third dimension
giving rise to string networks. We investigate the corresponding dynamics using
both stochastic and mean field theory simulations, showing that the coarsening
of these string networks follows a scaling law which is analogous to that found
in other physical systems in condensed matter and cosmology.
