Divergence theorem in curved space

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Discussion Overview

The discussion revolves around the application of the divergence theorem in the context of General Relativity (GR) and curved spacetime. Participants explore the implications of using the divergence theorem in curved spaces, the role of Killing vectors, and the interpretation of the Landau-Lifgarbagez pseudotensor in relation to gravitational forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about applying the divergence theorem in curved space, suggesting that it may not apply straightforwardly.
  • Another participant confirms that the divergence theorem does not apply in a straightforward manner in curved space.
  • There is a discussion about the necessity of using Killing vectors to define local radial lines for applying the divergence theorem in curved spacetime.
  • A participant questions whether the Landau-Lifgarbagez pseudotensor can be interpreted as representing an apparent force that can be eliminated by changing reference frames.
  • Another participant notes that the referenced link confirms much of the initial inquiry regarding pseudotensors in GR.
  • Participants inquire about the existence of other pseudotensors beyond the two they are familiar with.

Areas of Agreement / Disagreement

Participants generally agree that the divergence theorem does not apply straightforwardly in curved space, but there are varying interpretations of the implications and applications of pseudotensors, indicating unresolved aspects of the discussion.

Contextual Notes

Participants reference the need for specific mathematical constructs, such as Killing vectors and pseudotensors, to navigate the complexities of GR, but the discussion does not resolve the nuances of these concepts or their applications.

utesfan100
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I have been contemplating my confusion about my intuition regarding GR and believe I have tracked down the primary source of confusion.

The classical theories I have been taught assumed flat space with independent time and used the divergence theorem to derive inverse squared laws for fields. Despite GR holding a local form of the differential form of Gauss's law, every attempt to use the integral form is shot down immediately as not conforming to GR.

Am I correct to state that in a curved space the divergence theorem may not apply in a straight forward manner?

It appears that to use the divergence theorem in a curved space time one needs to use something called Killing vectors to define a curvilinear set of local radial lines to define a closed curve around a simply connected region in the curved space. I would think this would allow "local" to be extended from the infinitesimal range of the stress-energy tensor to a finite bounded volume.

Is this the proper interpretation for what the Landau-Lifgarbagez pseudotensor does for GR? ( http://en.wikipedia.org/wiki/Landau-Lifgarbagez_pseudotensor )

Since the Einstein Tensor is proportional to the Stress Energy tensor and also definable in terms of the metric alone it appears that these three tensors are three ways of describing the same mathematical object. Since the Landau-Lifgarbagez pseudotensor is defined in terms of the Einstein Tensor and the metric alone it can be defined in terms of the metric alone, and thus is another description of the same mathematical object.

Am I wrong to think that infinitesimally a pseudotensor represents an apparent force that can be eliminated by a change of reference frame? It would then seem reasonable that the Landau-Lifgarbagez pseudotensor represents the net unresolvable apparent force in a finitely bounded region caused by the spatial curvature in that finite volume.

Is this a correct way to think about gravity?
 
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utesfan100 said:
It references "many psuedo tensors" to do this task, while I have been exposed to only two. What other options exist?

I'm not sure, maybe try http://arxiv.org/abs/hep-th/9310025
 

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