Source: cirosantilli/perturbation-theory
= Perturbation theory
{wiki}
Used a lot in <quantum mechanics>, where the equations are really hard to solve. There's even a dedicated wiki page for it: https://en.wikipedia.org/wiki/Perturbation_theory_(quantum_mechanics)[]. Notably, <Feynman diagrams> are a way to represent perturbation calculations in <quantum field theory>.
Let's gather some of the best results we come across here:
* <Dirac equation solution for the hydrogen atom>