Feynman diagram

Outline Motivation Feynman integral Pertubation Thoery in Quantum Mechanics Pertubation Thoery in Quantum Field Theory Green Function Feynman Diagram Experimental Connection

Motivation Compared with experiments Amplitude of final states from collision of two initial particles Cross section of collision Graphical representation and simplicity

Pertubation Thoery in Quantum Mechanics Idea of Pertubation theory H = H_0 + H_I Acquire information from H_0 Getting new eigenvector

Pertubation Thoery in Quantum Mechanics Dyson series How wave function evolute by time when H = H_0 + H_I

Pertubation Thoery in Quantum Field Theory Idea of Quantum Field Theory Number of particle Take particle and wave as the same Solution (Feynman path integral approach)

Pertubation Thoery in Quantum Field Theory <final| exp( int_ (dt H_I)) |initial>

Ideal of Green function Two point Green function Four point Green function as combination of two point green function

Ideal of Green function Four point Green function as combination of two point green function

Feynman Diagram Green function + time evolution of field Graphical representation

Feynman Diagram Feynman rule: example of lampta Phy^4 theory

Feynman Diagram Re-intepretation of anti-particle Anti-particle in Dirac equation Anti-charge and positive energe

Experimental Connection Cross section What’s cross section? Connection of cross section and experiment

Experimental Connection Calculating cross section Amplitude Cross section