Is the Symmetry factor different in Path integral Formalism and the Perturbation theory (canonical) formalism? For example, the order-1 4-point cross X diagram in the $\phi^4$ theory has symmetry factor of $4!$ using Path integral Formalism, but has symmetry factor of $1$ using Wick contraction in perturbation formalism. Why different?

  • $\begingroup$ It has a symmetry factor of 1 in both cases $\endgroup$ – innisfree Jan 1 '16 at 21:24
  • $\begingroup$ Could you write your defn of a symmetry factor? $\endgroup$ – innisfree Jan 1 '16 at 21:33

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