COLLAPSE OF EXOTIC TEXTURES

The ordering of scalar fields after a phase transition in which a grou p G of global symmetries is spontaneously broken to a subgroup H provi des a possible explanation for the origin of structure in the Universe , as well as leading to observable effects in condensed-matter systems . The field dynamics can depend, in principle, on the geometry and top ology of the vacuum manifold G/H; for example, texture configurations which collapse and unwind will exist if the third homotopy group pi(3) (G/H) is nontrivial. We numerically simulate the evolution of texture like configurations in a number of different models, in order to deter mine the extent to which the geometry and topology of the vacuum manif old influence the field evolution. We find that the dynamics is affect ed by whether or not the theory supports strings or monopoles [charact erized by pi(1)(G/H) and pi(2)(G/H), respectively]. In some of the the ories studied, configurations with initially spherically symmetric ene rgy densities are unstable to nonspherical collapse; these theories ar e also found to nucleate defects during the collapse. Models that do n ot support monopoles or strings behave similarly to each other, regard less of the specific vacuum manifold.