Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

In the papers of the 1950s and 1960s, I see reference to anomalous threshold singularities. What are these? Is there a good reference that discusses this subject?

share|improve this question

1 Answer 1

"Anomalous" means that they're coming from quantum corrections, loops. "Threshold" means that they appear because some loop momenta approach a threshold for production at this very point – virtual particles are just becoming real. "Singularities" mean that these conditions obeyed by a loop Feynman diagram lead to a singular behavior in the resulting amplitude.

See e.g.


The last preprint mentions the anomalous threshold singularities in the context of their major application, the 1978 Coleman-Thun mechanism.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.