Why do we need gravitons if gravity comes from accelerated frames?

[diligence]

Hi. I'm a sophomore level undergrad trying to understand General Relativity (and all of physics for that matter) with the currently insufficient tools I possess. I was reading Einstein's book, "Relativity", and when I came to the section that describes gravity as the apparent force that arises from an accelerated frame, I couldn't help but wonder how this fits in with the current theoretical model of the "graviton". Why do we need a particle to explain a force that arises in this way? Is the accelerated frame model just an analogy used for easy access for newbies like me?

Any insight/elaboration would be greatly appreciated!

Thanks,
Bryan

 

[bcrowell]

Nobody actually has a model of gravity that involves gravitons. Gravitons are expected to be present in a quantum-mechanical theory of gravity, since quantum-mechanical theories of the other forces of nature involve the exchange of particles (e.g., quantizing electromagnetic waves involves photons). A quantum-mechanical theory of gravity would be expected to be relevant at a scale comparable to the Planck scale, and we don't have any experiments or observations at that scale.

 

[K^2]

You can linearize gravity. It's an approximate model, but it tends to work for a lot of situations. If you do so, you end up with field equations very much like Maxwell's equations. These can be second-quantized. That gives rise to gravitons in the simplest form.

If you understand a little bit of quantum field theory, try reading Feynman's lectures on gravity. Otherwise, you might need to learn some basics of QFT, preferably RQFT, before going into gravity. Some basic GR, at least on the level of differential geometry and covariant derivatives, would also be very helpful.

 

[bcrowell]

You can linearize gravity. It's an approximate model, but it tends to work for a lot of situations. If you do so, you end up with field equations very much like Maxwell's equations. These can be second-quantized. That gives rise to gravitons in the simplest form.

If you understand a little bit of quantum field theory, try reading Feynman's lectures on gravity. Otherwise, you might need to learn some basics of QFT, preferably RQFT, before going into gravity. Some basic GR, at least on the level of differential geometry and covariant derivatives, would also be very helpful.

This is a valid explanation of the motivation for gravitons, but to put this in perspective for the OP, this procedure does not result in a useful theory of quantum gravity. For a discussion of the issues involved, see section 14.1 of Wald.

 

[K^2]

I wouldn't say it isn't useful. It's clumsy. It doesn't do numerical predictions, at least not good ones. It breaks down completely under high space-time curvature. But it does give you some qualitative predictions that do work.