Graviton must have spin 2 according to GR, while photon has spin 1 according to quantum theory....why? And from where does that come from? Can we discuss? Schwarzschild radius is 2GM/c^2 according to GR, while quantum Schwarzschild radius is GM/c^2. From where the factor of 2 comes from in GR comparing to the point of view of quantum theory? 

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