Tutorial: Feynman diagrams, Part 2
Channel: Nils Berglund
Date: 2023-07-02

Feynman diagrams are a graphical way to compute complicated integrals arising in Quantum Field Theory by successive approximations. In this second part, we look at a version of the Euclidean Phi^4 model, which is closer to quantum field theories. We show how Feynman diagrams can be used to compute an expansion for two-point correlation functions. 

Intro: 0:00
Harmonic oscillator with noise: 2:18
Coupled springs: 6:20
Isserlis-Wick theorem: 10:51
Non-linear springs: 20:15
Schwinger-Dyson equations: 21:36
Graphical representation: 31:18
Does the series converge?: 41:52

Reference: D. C. Brydges, J. Fröhlich, et A. D. Sokal (1983), A new proof of the existence and nontriviality of the continuum φ42 and φ43 quantum field theories. Communications in Mathematical Physics, 91 : 141–186.
https://projecteuclid.org/euclid.cmp/1103940528

Outreach article (in French): 
https://images.math.cnrs.fr/Les-diagrammes-de-Feynman-1.html
https://images.math.cnrs.fr/Les-diagrammes-de-Feynman-2.html
https://images.math.cnrs.fr/Les-diagrammes-de-Feynman-3.html

#feynman #quantum #graphicalmethod