Furry's theorem

proper noun

In quantum electrodynamics, a theorem stating that if a Feynman diagram consists of a closed loop of fermion lines with an odd number of vertices, its contribution to the amplitude vanishes (and therefore a single photon cannot arise from the vacuum or be absorbed by it).

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Meanings

proper noun
  1. natural sciencesIn quantum electrodynamics, a theorem stating that if a Feynman diagram consists of a closed loop of fermion lines with an odd number of vertices, its contribution to the amplitude vanishes (and therefore a single photon cannot arise from the vacuum or be absorbed by it).

Origin

The theorem was derived by Wendell H. Furry in 1937.

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Cite this entry
APA

Furry's theorem. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/Furry's%20theorem

MLA

“Furry's theorem.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/Furry's%20theorem. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “Furry's theorem,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/Furry's%20theorem.

Source: Furry's theorem on Wiktionary, CC BY-SA 4.0.