I On the existence of Gravitational energy in General relativity

[KleinMoretti]

TL;DR Summary

what is the current view on gravitational energy

I was reading this paper that puts forward the argument that Gravitational energy in GR is unnecessary and doesn't exist and that got me wondering if this is a fringe theory or what exactly is the mainstream view regarding gravitational energy in GR?

Also does GR predict or need the existence of gravitational?

 

[PeterDonis]

You have had two previous threads on this same topic:

https://www.physicsforums.com/threads/dark-energy-and-conservation-of-energy.1062293/

https://www.physicsforums.com/threads/conservation-of-stress-energy-tensor.1062536/

The paper you reference here is saying basically the same thing as the Sean Carroll article that was referenced in that thread. It is just emphasizing the fact that there is no localized definition of "gravitational energy", whereas Carroll's article emphasized that in general there is no global "energy" that is conserved. And both of them tell you the same thing about local conservation of non-gravitational stress energy in GR: yes, that conservation law is valid, in all spacetimes: the covariant divergence of the stress-energy tensor is always zero. But that is the only conservation law that always holds in GR.

None of these answers will change no matter how many times you ask the question or how many different papers you read.

 

[PeterDonis]

does GR predict or need the existence of gravitational?

The answer to this should be obvious from my previous post and the previous threads you have already had on this topic.

 

[KleinMoretti]

You have had two previous threads on this same topic:

https://www.physicsforums.com/threads/dark-energy-and-conservation-of-energy.1062293/

https://www.physicsforums.com/threads/conservation-of-stress-energy-tensor.1062536/

The paper you reference here is saying basically the same thing as the Sean Carroll article that was referenced in that thread. It is just emphasizing the fact that there is no localized definition of "gravitational energy", whereas Carroll's article emphasized that in general there is no global "energy" that is conserved. And both of them tell you the same thing about local conservation of non-gravitational stress energy in GR: yes, that conservation law is valid, in all spacetimes: the covariant divergence of the stress-energy tensor is always zero. But that is the only conservation law that always holds in GR.

None of these answers will change no matter how many times you ask the question or how many different papers you read.

I don’t think in any of the posts you linked the question of whether or not gravitational energy is real comes up at all, also I don’t think that the Sean Carroll article argues that gravitational energy doesn’t exist unlike the paper that I linked that flat out says that it doesn’t.

 

[KleinMoretti]

The answer to this should be obvious from my previous post and the previous threads you have already had on this topic.

By this I’m guessing you mean yes, since I’m those posts you mentioned are all under the assumption that it does exist, which is exactly what I meant in my question, is general relativity formulated under the assumption that gravitational energy is real.

 

[PeterDonis]

I don’t think in any of the posts you linked the question of whether or not gravitational energy is real comes up at all

That's because "real" is not a scientific term. So questions about what is "real" are not scientific questions.

those posts you mentioned are all under the assumption that it does exist

I have no idea what you're talking about.

is general relativity formulated under the assumption that gravitational energy is real

Again, "real" is not a scientific term. So your question is unanswerable.

 

[PeterDonis]

@KleinMoretti if you want to formulate a question that would be answerable, you need to think carefully about what observations and measurements you could make about "gravitational energy" and what their results would tell you. I would suggest reading the literature with that in mind. (If you read the paper you referenced in the OP carefully, you will see that, while it does use terms like "real" and "exist", and their opposites, it gives a meaning to those terms that ultimately comes down to actual observations and measurements, and how those are represented in GR.)

This thread is closed.