This discussion focuses on the differences between Feynman diagrams in position space and momentum space, particularly in the context of Compton scattering. It is established that while the diagrams may appear different in their orientation, they are topologically equivalent, meaning the mathematical expressions representing them remain unchanged. The internal electron line's orientation varies between position and momentum space, but this does not affect the underlying physics described by the diagrams. Understanding these distinctions is crucial for exam preparation in quantum field theory.
PREREQUISITESStudents preparing for exams in quantum field theory, physicists interested in particle interactions, and anyone seeking to deepen their understanding of Feynman diagrams in different spaces.
madness said:What is the difference when drawing diagrams in momentum space and position space? In my notes the 2 lowest order diagrams for Compton scattering look quite different in momentum and position space. In position space the internal electron line in the second diagram points horizontally in position space and vertically in momentum space. What does this mean?
The actual diagrams are the same in every basis, only the mathematical expressions representing the diagrams are different. As for your question about the internal electron line: if two diagrams only differ by some sort of rotation of propagator lines, the diagrams are the same (topologically equivalent), since when you write down the mathematical expression for the diagram, all that matters is the relative positioning of vertices and lines. The orientation of lines does not step into equations.madness said:What is the difference when drawing diagrams in momentum space and position space? In my notes the 2 lowest order diagrams for Compton scattering look quite different in momentum and position space. In position space the internal electron line in the second diagram points horizontally in position space and vertically in momentum space. What does this mean?