Wick's Theorem expresses the time-ordered product of a collection of field operators in quantum field theory as a sum of normal-ordered products together with every possible way of pairing operators into contractions. Named for Gian-Carlo Wick, it supplies the combinatorial machinery underlying perturbative Feynman-diagram calculations, translating products of operators into sums indexed by pairings.
Facts
StatementWick's theorem is a method of reducing a time ordered product of creation and annihilation operators into a sum of normal ordered products together with every possible way of pairing operators into contractions, turning the calculation into a combinatorics problem. 1 Classification
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Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.
Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.
Sources
1. Wick's theorem, Wikipedia
Lead section, opening sentence
Wick's theorem is a method of reducing high-order derivatives to a combinatorics problem.
References, Wick 1950 citation
Wick, G. C. (1950). "The Evaluation of the Collision Matrix". Phys. Rev. 80 (2): 268-272.
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