Numerical simulation of cosmic-string evolution in flat spacetime.

Abstract

We present a numerical simulation of the evolution of a system of cosmic strings in flat spacetime. Our algorithm for the string dynamics exactly integrates the Nambu equation of motion. The strings are represented by discrete points on a spatial lattice, allowing an intercommuting algorithm which exactly preserves all relevant quantities. We find that the system evolves to a steady state in which most of the energy is in loops of the smallest size allowed in the simulation. ``Infinite'' strings present in the initial state fragment into a distribution of small loops. In the absence of an energy cutoff there is no equilibrium, and the steady state artificially imposed by the cutoff bears no resemblance to the initial state.