Divergence theorem in curved space

In summary, the conversation discusses the confusion surrounding the use of the divergence theorem in relation to General Relativity (GR). It is noted that in a curved space, the application of the divergence theorem may not be straightforward and requires the use of Killing vectors. The Landau-Lifgarbagez pseudotensor is mentioned as a way to define a closed curve in a region of curved space and eliminate apparent forces. The conversation also references other options for dealing with this issue, such as using multiple pseudotensors.
  • #1
utesfan100
105
0
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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  • #3
atyy said:

EXCELLENT LINK! If I am reading it correctly, it confirms most of what I asked above!

It references "many psuedo tensors" to do this task, while I have been exposed to only two. What other options exist?
 
  • #4
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
 

1. What is the Divergence theorem in curved space?

The Divergence theorem in curved space is a mathematical principle that relates the flow of a vector field through a closed surface to the divergence of the field within the enclosed volume. It is a generalization of the traditional Divergence theorem in flat space to curved spaces, such as a curved surface or a three-dimensional manifold.

2. What is the significance of the Divergence theorem in curved space?

The Divergence theorem in curved space is an important tool in many areas of physics and engineering, such as fluid dynamics, electromagnetics, and general relativity. It allows for the calculation of flux and volume integrals in curved spaces, which can be used to solve complex problems in these fields.

3. How is the Divergence theorem in curved space derived?

The Divergence theorem in curved space is derived using the concept of covariant derivatives, which take into account the curvature of the space. It involves the use of differential geometry and tensor calculus to express the theorem in a general form that is applicable to any curved space.

4. Can the Divergence theorem in curved space be applied to any type of surface?

Yes, the Divergence theorem in curved space can be applied to any type of surface, whether it is a smooth curved surface, a rough surface, or a surface with holes. As long as the surface is closed and the vector field is well-behaved within the enclosed volume, the theorem can be used to calculate flux and volume integrals.

5. Are there any limitations to the Divergence theorem in curved space?

The Divergence theorem in curved space has limitations in cases where the vector field is not well-defined, or when the surface is not closed. In these situations, the theorem may not hold, and alternative methods may need to be used to calculate flux and volume integrals. Additionally, the theorem is only valid in spaces with a defined metric, such as Riemannian manifolds.

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