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• Green's function and Feynman diagrams Helpful for generating and calculating the collection of diagrams, seeing how they relate to Wick's theorem.
• Tobias Osborne. Quantum Field Theory.
  • lecture notes. Especially relevant for me is his Lecture 9 where he starts talking about Feynman diagrams.

读物

• R. E. Borcherds, A. Barnard. Lectures on Quantum Field Theory P.25
• Krešimir Kumerički. Feynman Diagrams for Beginners. Helpful for understanding the related physics, but doesn't explain how to generate all the diagrams.
• Thomas Strohm. A short tutorial on Green's functions. I plan to study this tutorial to understand the connection between Wick's theorem, Green's functions and Feynman diagrams.
• How to count symmetry factors of Feynmann diagrams?
• Abdelmalek Abdesselam. Feynman Diagrams in Algebraic Combinatorics Species.
• Michael Borinsky. Combinatorics of Feynman diagrams and algebraic lattice structure in QFT
• Dong et al. Symmetry Factors of Feynman Diagrams for Scalar Fields
• Birdtracks A readable but very advanced book that uses the diagrams as "birdtracks" for rethinking the classification of Lie algebras:
• Abdelmalek Abdesselam. Feynman Diagrams in Algebraic Combinatorics.
• John Baez. Higher-Dimensional Algebra.
• John C. Baez and James Dolan. From Finite Sets to Feynman Diagrams.

Ideas

Wick's theorem.

• Goal of calculation is to reorganize the time ordered operators so that they are normal ordered operators, in that the particle creation appears before the particle annihilation.
• Wick's contraction interprets the double factorial in terms of pairs of connections.

Feynman diagrams

• In Feynman diagrams, charge means that lines are oriented. Chargeless are not oriented.
• Feynman diagrams distinguish local changes (at vertices) and nonlocal changes (motion). Local changes occur at "the present".
• Feynman diagrams are thought of as morphisms in monoidal categories.
• Feynman diagram sets up the grounds for the foursome, fivesome, sixsome, sevensome. The incoming wires are Why and How and outgoing are Whether and What and thus the two causalities are related. But the directions of the causalities can get twisted around by the various divisions.

Notes

• Ask Thomas: Why 4 branches and not 3 or 6 or 8 and so on?
• https://indico.cern.ch/event/421552/sessions/170249/attachments/884224/1242865/feynman.pdf
• https://www.pas.rochester.edu/assets/pdf/undergraduate/Calculating_Transition_Amplitudes_from_Feynman_Diagrams.pdf
• How could cell complexes relate to Feynman diagrams and create space?
• Link (edge) between two interactions (vertices) - kinematics - step {$\alpha$} in one direction - step {$\beta$} in the opposite direction
• {$\alpha$} and {$\beta$} describes the connection between a local coordinate system (centered on the particle) and the global coordinate system (which it moves with regard) - thus the duality of a particle and its coordinates
• Why aren't there Feynman diagrams for three fields? Is it because of conservation of momentum?
• Can Feynman diagrams for two fields be interpreted as a mass traveling?
• A Guide to Feynman Diagrams in the Many-Body Problem: Feynman Diagrams, or How to Solve the Many-body problems by means of Picture based on Chapter 1 of Richard D. Mattuck. A Guide to Feynman Diagrams.
• Quanta Magazine. How Feynman Diagrams Revolutionized Physics.
• Do Feynman diagrams organize the eight emotional responses (with suspense in the middle)? Does this express 5+3=0?
• Feynman diagram. Momentum k is attributed to lines. Steps in the combinatorics of orthogonal polynomials express momentum.

Feynman diagrams

• Mathemaniac. Green's functions: the genius way to solve DEs.
• Dirac delta distribution is a probability distribution that models certainty. Thus it is discontinuous as a probablity density because it is zero everywhere except for at a particular point. So its value is discontinuous at that point both from the left and from the right.
• Virtual particles do not have speeds - thus do not conserve momentum or energy.