Fluctuations and phase transition dynamics

Kibble and Zurek have provided a unifying causal picture for the appearance of classical defects like cosmic strings or vortices at the onset of phase transitions in relativistic QFT and condensed matter systems, respectively . In condensed matter the predictions are partially supported by agreement with experiments in superfluid helium. We provide an alternative picture fo r the initial appearance of defects that supports the experimental evidence . When the original predictions fail, this is understood, in part, as a con sequence of thermal fluctuations (noise), which play a comparable role in b oth condensed matter and QFT.