NUMERICAL-METHODS IN COSMOLOGICAL GLOBAL TEXTURE SIMULATIONS

Numerical simulations of the evolution of a global topological defect field have two characteristic length scales-one macrophysical, of the order of the field correlation length, and the other microphysical, of the order of the field width. The situation currently of most interest to particle cosmologists involves the behavior of a grand unification theory (GUT)-scale defect held at the epoch of decoupling, where the ratio of these scales is typically of the order of 10(50). Such a ratio is unrealizable in numerical work, and we consider the approximations which may be employed to deal with this. Focusing on the case of global texture we outline the implementation of the associated algorithms, and in particular note the subtleties involved in handling texture unwinding events. Comparing the results in each approach then establishes that, subject to certain constraints on the minimum grid resolution, the methods described are both robust and consistent with one another.