I am quite familiar with the proof of Weinberg Witten (WW) theorem. One major result which follow from WW is that the graviton cannot be a composite particle. I have 2 questions here:
How do we tell (in the theory) whether something is a composite particle or not? It should be an irreducible reps of the Poincare group, right? The confusion I have here is that an electron is a Dirac fermion, but the Dirac reps is a reducible one. There is something amiss here. Essentially, the question here is that how to distinguish between elementary and composite particles, in the theory?
How to use the Weinberg-Witten theorem to show that the graviton cannot be a composite particle? Can anyone explain this a bit intuitively.