A spontaneous symmetry breaking chooses order-parameter directions independently in regions that have not been in causal contact. Mismatches around disconnected components, loops or enclosing spheres can trap domain walls, cosmic strings or magnetic monopoles. The correlation length cannot exceed the causal horizon, so one monopole per horizon volume estimates the smallest causal initial abundance up to geometrical and efficiency factors.
// Target: classical-field-theory-soliton.bigb
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