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EldwinSchrodinger @ Feynman Diagrams
EldwinSchrodinger @ Feynman Diagrams
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Feynman diagrams are graphical ways to represent exchange forces. Each point at which lines come together is called a vertex, and at each vertex one may examine the conservation laws which govern particle interactions. Each vertex must conserve charge, baryon number and lepton number.
Developed by Feynman to decribe the interactions in quantum electrodynamics (QED), the diagrams have found use in describing a variety of particle interactions. They are spacetime diagrams, ct vs x. The time axis points upward and the space axis to the right. (Particle physicists often reverse that orientation.) Particles are represented by lines with arrows to denote the direction of their travel, with antiparticles having their arrows reversed. Virtual particles are represented by wavy or broken lines and have no arrows. All electromagnetic interactions can be described with combinations of primitive diagrams like this one.
Only lines entering or leaving the diagram represent observable particles. Here two electrons enter, exchange a photon, and then exit. The time and space axes are usually not indicated. The vertical direction indicates the progress of time upward, but the horizontal spacing does not give the distance between the particles.
Other electromagnetic process can be represented, as in the examples below. A backward arrow represents the antiparticle, in these cases a positron. Keep in mind that time progresses upward, and that a downward arrow is not a particle progressing downward, but an antiparticle progressing upward ( forward in time).
After being introduced for electromagnetic processes, Feynman diagrams were developed for the weak and strong interactions as well. Forms of primitive vertices for these three interactions are
Particle interactions can be represented by diagrams with at least two vertices. They can be drawn for protons, neutrons, etc. even though they are composite objects and the interaction can be visualized as being between their constituent quarks.
Labels: Quantum Mechanics
