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I’m currently studying for a particle physics module about the standard model and there is a lot of material on Lagrangians (curly L) and actions (S).
I’m not quite sure what both of these quantities signify/mean physically. From what I gather a Lagrangian kind of describes the energies that contribute to particular forms of matter but I may be wrong.
If anyone can give me a reasonably simple description of what these quantities do/describe I would appreciate it.