Anthropic Considerations in Multiple-Domain Theories and the Scale of Electroweak Symmetry Breaking

One of the puzzles of the standard model is why the mass parameter {mu}{sup 2} , which determines the weak interaction scale, is closer to the quantum chromodynamics scale than to the grand unification or Planck scales. We consider a novel approach to this problem, based upon the idea that {mu}{sup 2} takes different values in different domains of the Universe. The whole range of values for {mu}{sup 2} , from +M{sup 2}{sub P} to {minus}M{sup 2}{sub P} , is explored, and it is found that only for values in a narrow window is life likely to be possible. The observed value of {mu}{sup 2} is fairly typical of the values in this window. {copyright} {ital 1998} {ital The American Physical Society}