Why Can't Photons Have a Spin of 0 Like Gravitons?

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SUMMARY

The discussion clarifies the spin characteristics of photons and gravitons. Photons possess a spin of 1, allowing only helicity states of -1 and +1, while gravitons, with a spin of 2, can exhibit helicity states of -2, -1, 0, 1, and 2. The prohibition of a spin state of 0 for photons is attributed to their massless nature and the constraints of the Poincaré group representation. The graviton's spin representation is a traceless second-rank symmetric tensor, which explains its allowed spin states.

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The graviton has a spin of 2. So, that means the graviton can take possible spins: -2, -1, 0, 1, 2 ? Just want to make sure since, for a photon, even if it's spin 1, it can only take two possibilities, i.e. -1 and +1. 0 is not allowed.
 
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Well, not really. The P-F field has 2 degrees of freedom in 4 space-time dimensions and thus the eigenvalues for the helicity operarator are only +2 and -2.

Daniel.
 
touqra said:
The graviton has a spin of 2. So, that means the graviton can take possible spins: -2, -1, 0, 1, 2 ? Just want to make sure since, for a photon, even if it's spin 1, it can only take two possibilities, i.e. -1 and +1. 0 is not allowed.

Do you know why the 0 is not allowed for photon? For similar reason the
(-1,0,1) are not allowed for graviton.(massles field,Traceless 2nd rank symmetric tensor rep of Poincare group).


regards

sam
 

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