Discussion Overview
The discussion revolves around the conserved quantities in Feynman diagrams, focusing on what is conserved at individual nodes and across the entire diagram. It touches on theoretical aspects of particle physics as presented in Griffiths' book.
Discussion Character
- Technical explanation, Conceptual clarification, Debate/contested
Main Points Raised
- Some participants propose that at each node of a Feynman diagram, quantities such as 3-momentum and spin are conserved in position representation, while 4-momentum and spin are conserved in momentum representation.
- Others argue that the entire diagram conserves 4-momentum and spin, representing a complete physical reality.
- One participant mentions that unitarity is conserved over the sum of all Feynman diagrams and that typically all currents and charges are conserved, although anomalies can occur that violate certain symmetries.
- Another participant suggests that every property of a particle, including momentum, charge, spin, isospin, hypercharge, strangeness, baryon number, lepton number, and color, is conserved at the node level.
- A later reply challenges the conclusion that all properties are conserved across the entire diagram, noting that divergent terms may arise that violate global symmetries after renormalization, specifically referencing the triangle anomaly.
Areas of Agreement / Disagreement
Participants express differing views on the extent of conservation across the entire diagram, with some asserting that all properties are conserved while others highlight potential violations due to anomalies. The discussion remains unresolved regarding the implications of these anomalies.
Contextual Notes
Limitations include the dependence on definitions of conserved quantities and the unresolved nature of how anomalies affect global symmetries in the context of renormalization.
