What are Feynman diagrams in particle physics?

Feynman diagrams are graphical representations used to calculate and understand the behaviour of subatomic particles in quantum physics.

Feynman diagrams are named after their creator, the American physicist Richard Feynman. They were first introduced in the 1940s as a way to simplify the complex calculations involved in quantum electrodynamics (QED), a theory that describes how light and matter interact. Feynman diagrams have since become a fundamental tool in particle physics, used to depict all kinds of particle interactions.

A Feynman diagram consists of lines and vertices. The lines represent particles, while the vertices, where lines meet, represent interactions between particles. There are different types of lines to represent different types of particles. For example, straight lines with arrows represent fermions (matter particles), wavy lines represent photons (light particles), and dashed lines represent scalar bosons. The direction of the arrows on the lines indicates the direction of time, from past to future.

The beauty of Feynman diagrams is that they not only provide a visual representation of particle interactions, but they also provide a mathematical formula for calculating the probability of these interactions. Each part of the diagram corresponds to a mathematical term, and by adding up all the terms for all possible diagrams, physicists can calculate the probability of a particular interaction occurring.

For example, consider a simple interaction where an electron and a positron annihilate each other to produce a photon, which then decays into another electron and positron. This interaction can be represented by a Feynman diagram with two straight lines meeting at a vertex to represent the annihilation, a wavy line to represent the photon, and two more straight lines meeting at another vertex to represent the decay. The corresponding mathematical formula can then be used to calculate the probability of this interaction.

In conclusion, Feynman diagrams are a powerful tool in particle physics, providing a visual and mathematical way to understand and calculate particle interactions. They are a testament to the creativity and ingenuity of physicists in their quest to understand the fundamental workings of the universe.