Could the quanta of gravity be something other than a spin-2 graviton?

[ensabah6]

GR predicts gravitational waves, and QM says all waves are also particles.

But does the particle of gravity have to be a spin-2 graviton? could the particle of gravity be, for example, a quanta of space-time curvature?

 

[Coin]

As I understand things, if you have a spin 2 boson, it HAS to be the quanta of gravity.*

But there's no rule saying it has to go the other way-- just because you have quantum gravity, doesn't mean you have to have a spin 2 boson.

This is just what I've been told.

* I've seen it claimed a couple of times on this forum that there is actually a proof that any spin 2 boson has to be the quanta of gravity, and it was claimed that this proof was written by Feynman. I'd be very curious to see that if anyone knows where to find it!

 

[ccdantas]

Take a look at:

http://egregium.wordpress.com/2007/05/24/is-there-more-to-gravity-than-gravitons/

 

[notknowing]

no gravitons

GR predicts gravitational waves, and QM says all waves are also particles.

But does the particle of gravity have to be a spin-2 graviton? could the particle of gravity be, for example, a quanta of space-time curvature?

I think there does not even exist a graviton. Gravitation could be an induced force, resulting from all the other forces (original idea of Sakharov). Also, it is clear (for me) that describing gravitation by means of virtual particles quickly leads to a contradiction:
Let us suppose indeed that they exist. Even if they are supposed to be (rest)massless spin 2 particles, they should contribute to the total energy of the system, just like the virtual (massless) photons of the electromagnetic field somehow contribute to the mass of the system. The nonlinear character of the Einstein equations also seems to indicate that the "gravitational field" itself gravitates (I know this is strictly not correct, I use this only to guide the intuition). So, if the gravitons themselves are subject to the gravitational field, one should have virtual gravitions exchanging between these gravitons and other gravitons or other masses - AND - you can not stop this process: you just have to keep on adding gravitons to include all the reactions. So, you get an infinite number of gravitons per unit volume resulting in an infinite energy density and the whole of space would be just a massive "block" of gravitons. A ridiculous situation. This proofs that gravitons can not exist.


Rudi Van Nieuwenhove

 

[samalkhaiat]

As I understand things, if you have a spin 2 boson, it HAS to be the quanta of gravity.*

You have not understood "things" correctly! even atoms can be a spin 2 bosons. Have you heard about particles called the tensor mesons?

But there's no rule saying it has to go the other way-- just because you have quantum gravity, doesn't mean you have to have a spin 2 boson.

It can be shown that "massless" "spin-2" object does satisfy the LINEARIZED Einstein equations, hence the name GRAVITON.

regards

sam

 

[friend]

GR predicts gravitational waves, and QM says all waves are also particles.

But does the particle of gravity have to be a spin-2 graviton? could the particle of gravity be, for example, a quanta of space-time curvature?

In "QFT in curved spacetime", Robert Wald states that in highly curved or fast changing gravitational field there is no particle interpretation of QFT; it's all just fields. So strictly speaking, in high curvature or fast changing gravitational fields, there are no particles at all - not even gravitons.

 

[Orbb]

Sorry for refreshing this older thread. So does http://arxiv.org/abs/gr-qc/0409089 have any implications for the way gravity arises in string theory? Is it only the linearized relativity that can be obtained?