# Higher spin fields

I was told that the existence of higher spin fields whose spin is higher than 2 is forbidden by "equivalence principle" of GR(general relativity).

But after considering about it, I can't understand why equivalence principle could imply the nonexistence of higher spin fields (>2).

Could anyone explain this?
Thanks

## Answers and Replies

I cannot understand such a statement.
A wheel from my bicycle has very often a spin incredibly much larger than 2.

If you don't have first-hand information, better forget it completely.
But if you can have an explanation of this statement, tell me, I would like to know.

Maybe the whole point lies in the word "field" and a wheel has no relation to a field!
First of all, why was it that photons have spin 1?
And why should quantum gravity be a spin 2 field?
I think in both cases this can be traced back to the form of the classical Lagragian.
I can only remember how that goes for electrodynamics.

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It's called the Weinberg Witten theorem, that's all I can say to u.

A. Neumaier
I was told that the existence of higher spin fields whose spin is higher than 2 is forbidden by "equivalence principle" of GR(general relativity).

This is a very inaccurate statement. A more accurate version from http://en.wikipedia.org/wiki/Weinberg–Witten_theorem says:
''no massless (composite or elementary) particles with spin j greater than one are consistent with any renormalizable Lorentz-invariant quantum field theory excluding only (nonrenormalizable) theories of gravity and supergravity.''

References to the original papers (where you can find more details about the precise meaning of this statement) are given there, too.

tom.stoer
Nevertheless there is an argument that spin greater than 2 is forbidden completely.

questions:
- how does the argument for spin > 1 work?
- how does the argument for spin > 2 work?
- how does SUSY bypass the first argument? what is the loophole?

A. Neumaier