What is a Feynman diagram?
Q: What is a Feynman diagram?
A: A Feynman diagram is a diagram that shows what happens when elementary particles collide. It consists of lines in different shapes—straight, dotted, and squiggly—which meet up at points called vertices. The vertices are where the lines begin and end, and represent two or more particles that happen to be at the same point in space at the same time.
Q: What do the lines in a Feynman diagram represent?
A: The lines in a Feynman diagram represent the probability amplitude for a particle to go from one place to another. They can also be interpreted forward or backwards in time, so that if a particle disappears into a meeting point, it either means that the particle was created or destroyed depending on its direction in time.
Q: How do you calculate the total probability amplitude for a collision?
A: You calculate this by multiplying together all of the probability amplitudes for each line and vertex, then adding up all these probability amplitudes over all possible meeting points with an appropriate weight. This gives you the total probability amplitude for a collision in a particle accelerator which tells you how likely it is for particles to bounce off one another in any particular direction.
Q: Who invented Feynman diagrams?
A: Feynman diagrams were named after Richard Feynman who won the Nobel Prize in Physics. He developed them as part of his work on quantum electrodynamics (QED).
Q: What kind of particles are involved with QED?
A: In QED there are only two kinds of particles - electrons (little particles inside atoms) and photons (particles of light). The only thing that can happen is that an electron (or its antiparticle) can emit (or absorb) a photon, so there is only one building block for any collision.
Q: What does an imaginary part signify when talking about emission probabilities?
A: An imaginary part signifies the charge of an electron when talking about emission probabilities within QED theory.
