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The term "coupling" between quantum fields refers to certain terms in the Lagrangian (density) $\mathcal{L}$ where the respective field operators appear together, e.g. $g\phi^\dagger\psi $ with coupling constant $g$.

Knowing the mathematical description/origin of a coupling in QFT, I wonder: How can a quantum field $\phi$ of a certain kind excite a quantum state of another totally unrelated type of quantum field $\psi$? Is there are more "physical" picture of how the coupling really happens instead of just a mathematical one?

Qmechanic
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quantumorsch
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1 Answers1

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Well, all the fields exist in the same space, right? So they occupy the same volume. Perhaps the different fields are actually different vibrational mode families of something finer; in that case, coupling isn't surprising, since we're observing different vibrational mode families of the same underlying field. There is probably partial overlap of the frequencies between the mode families, perhaps this is the origin of coupling?

Alexandre
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