I Linearized Gravity: Bimetric Theory of General Relativity?

[dsaun777]

Is the linearized gravity that describes the gravitational waves of general relativity a bimetric theory of gravity? Your adding the flat spacetime metric of minkowski spacetime to the perturbed metric, usually denoted h, to arrive at g.

 

[PeterDonis]

Is the linearized gravity that describes the gravitational waves of general relativity a bimetric theory of gravity?

No.

Your adding the flat spacetime metric of minkowski spacetime to the perturbed metric, usually denoted h, to arrive at g.

No, you're expressing the metric g, to linear order, as a sum of the flat metric and the perturbation. That doesn't mean there are two metrics in the theory. It just means you're expressing the single metric in a useful form given that the perturbation is small.

 

[dsaun777]

No.No, you're expressing the metric g, to linear order, as a sum of the flat metric and the perturbation. That doesn't mean there are two metrics in the theory. It just means you're expressing the single metric in a useful form given that the perturbation is small.

How does this differ from bimetric theory? What's the benefit of a bimetric theory over just adding another dimension to General
Relativity?

 

[PeterDonis]

How does this differ from bimetric theory?

A bimetric theory says there are two different physical metrics. In linearized gravity there is only one physical metric, g.

 

[PeterDonis]

What's the benefit of a bimetric theory over just adding another dimension to General
Relativity?

I'm not sure what you mean by "adding another dimension to General Relativity", since that has nothing to do with what linearized gravity does.

As for the benefits of bimetric theory, you would have to ask its proponents.

 

[dsaun777]

I'm not sure what you mean by "adding another dimension to General Relativity", since that has nothing to do with what linearized gravity does.

As for the benefits of bimetric theory, you would have to ask its proponents.

Are there any proponents of the theory here? I'm not suggesting linearized gravity does have any to do with higher dimensions.

 

[PeterDonis]

Are there any proponents of the theory here?

Not that I'm aware of. If you can give a specific reference to a paper that describes the bimetric theory of gravity you are interested in, you might have a better chance of getting the attention of someone who knows about it.

 

[PAllen]

Bimetric theories have been used to explore the possibility of different speed for EM radiation and gravitational waves, i.e. as test theories. Here is an example:

https://arxiv.org/abs/gr-qc/0403060

 

[dsaun777]

Not that I'm aware of. If you can give a specific reference to a paper that describes the bimetric theory of gravity you are interested in, you might have a better chance of getting the attention of someone who knows about it.

No specific paper in general. I just wanted to have some people interject their thoughts on a variable a speed of gravity or speed of light.