Pattern formation in the early universe - art. no. 083511

Systems that exhibit pattern formation are typically driven and dissipative . In the early universe, parametric resonance can drive explosive particle production called preheating. The fields that are populated then decay quan tum mechanically if their particles are unstable. Thus, during preheating, a driven-dissipative system exists. We have shown previously that pattern f ormation can occur in two dimensions in a self-coupled inflaton system unde rgoing parametric resonance. In this paper, we provide evidence of pattern formation for more realistic initial conditions in both two and three dimen sions. In the one-held case, we have the novel interpretation that these pa tterns can be thought of as a network of domain walls. We also show that th e patterns are spatio-temporal, leading to a distinctive, but probably low- amplitude peak in the gravitational wave spectrum. In the context of a two- field model, we discuss putting power from resonance into patterns on cosmo logical scales, in particular to explain the observed excess power at 100h( -1) Mpc, and why this seems unlikely in the absence of a period of post-pre heating inflation. Finally we note our model is similar to that of the deca y of disoriented chiral condensates and therefore pattern formation may als o occur at BNL RHIC and CERN LI-IC.