![perturbation theory - How can a Dirac delta function that does not occur under an integral be used to describe a transition rate? - Physics Stack Exchange perturbation theory - How can a Dirac delta function that does not occur under an integral be used to describe a transition rate? - Physics Stack Exchange](https://i.stack.imgur.com/mQzh5.png)
perturbation theory - How can a Dirac delta function that does not occur under an integral be used to describe a transition rate? - Physics Stack Exchange
Everything is Physics - The Dirac delta function δ(x) is a distribution on the real line which equals zero everywhere except at zero, with an integral of one over the entire real
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