ABSTRACT
In chapter 6 we developed propagator methods which allowed us to calculate transition amplitudes using the S-matrix. In chapter 8 we calculated the lowest-order S-matrix elements for several quantum electrodynamic processes. In each case, we also drew diagrams in space-time, or graphs, that allowed us to visualize the process. Based on observations, we identified elements of each diagram with factors in the S-matrix elements. We gained enough experience to extract a set of rules – the Feynman rules – which in principle allow the calculation of any quantum electrodynamic process no mater how complicated. The set of diagrams in which each vertex is connected to every other vertex by only one internal line are called tree diagrams. In this appendix, we summarize the Feynman rules for tree diagrams.
