When calculating scattering cross-sections in particle physics, the interaction between particles can be … See more

In their presentations of fundamental interactions, written from the particle physics perspective, Gerard 't Hooft and Martinus Veltman gave good arguments for taking the original, non-regularized Feynman d… See more

A Feynman diagram is a representation of quantum field theory processes in terms of particle interactions. The particles are represented by the diagram lines. The lines can be squiggly or straight, with an arrow or without, de… See more

A Feynman diagram represents a perturbative contribution to the amplitude of a quantum transition from some initial quantum state to some final quantum state.
For example, in the process of electron-positron an… See more

The probability amplitude for a transition of a quantum system (between asymptotically free states) from the initial state |i⟩ to the final state | f ⟩ is given by the matrix element
where S is … See more

In a path integral, the field Lagrangian, integrated over all possible field histories, defines the probability amplitude to go from one field configuration to another. In order to make sense, the field theory must have a well-defined … See more