# Infrared modification of General relativity

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General relativity can be derived as the only consistent effective field theory for interacting spin two particles. If this statement is correct , this makes the study of modified gravity with torsion , like the sciama kibble theory and also teleparallel gravity on weitzenbochs manifolds irrelevant and a waste of time. So , Why do people study these theories ?

If somebody is interested in studying those theories and he gets funding for doing his research, then nothing prevents him from such an activity.

Be aware of consensus. Actually, students learn at least one theory based on flawed experiments and it is forbidden to say the contrary with the risk to be banned from grants. More trivially, in the 7ties and 8ties, students were learning 'fundamental' limitations on data bandwith while engineers were joking about. Add to these considerations the intrinsic beauty of maths ...

''the only consistent effective field theory for interacting spin two particles''. - you should give a reliable source for such an unlikely claim!

It is very well known that in four dimensions one can only have a field theory with up to spin 2 particles that is Lorentz invariant, unitary, etc such that it has non-trivial $S$-matrix. This is directly related to the Coleman-Mandula theorem and I disagree that this claim needs justification in PO. As for the actual question.. good question.

@conformal_gk: A non trivial S-matrix implies some interaction. I am afraid this is the key to undertsand what the Coleman-Mandula theorem says. I just want to underline that the "interaction term" may be quite different from what is currently implied and then other possibilities open.

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