Can the Ricci Scalar Depend on Spacetime Coordinates?

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    Ricci scalar Scalar
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Discussion Overview

The discussion revolves around the nature of the Ricci Scalar in relation to spacetime coordinates, particularly whether it can be a function of those coordinates. Participants explore theoretical implications and specific cases, touching on concepts from general relativity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if the Ricci Scalar can depend on spacetime coordinates, noting that their previous calculations consistently returned it as a constant.
  • Another participant explains that while the Ricci Scalar is computed from the metric tensor, its dependence on coordinates can vary; it may remain constant even if the metric components change.
  • A third participant confirms that their metric does vary with the coordinates, suggesting a potential for the Ricci Scalar to also vary.
  • Another participant introduces the idea that in certain spacetimes, such as the Lemaitre-Tolman-Bondi models, the Ricci tensor can be adjusted based on the density of the dust configuration, implying flexibility in its behavior.

Areas of Agreement / Disagreement

Participants express differing views on the dependence of the Ricci Scalar on spacetime coordinates, with no consensus reached on whether it can or cannot vary based on the metric tensor's components.

Contextual Notes

The discussion highlights the complexity of the relationship between the Ricci Scalar and the metric tensor, with some participants noting specific cases where the behavior may differ, but without resolving the underlying assumptions or conditions that affect this relationship.

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Does it make sense for the Ricci Scalar to be a function of the spacetime coordinates?

In previous calculations I have carried out in the past, everytime the Ricci Scalar has been returned as a constant, rather than being explicitly dependent on the coordinates.

Thanks for any replies
 
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The value of the Ricci scalar can be computed using only the metric tensor, and the components of the metric tensor may or may not vary with spacetime coordinates. So a Ricci scalar might change as your coordinates change, but it might not. Due to all the contractions, the Ricci scalar might be constant even if the components of the metric change (as with the surface of a sphere), but this varies from case to case.
 
Thank you for your reply. My metric does indeed vary with the coordinates.
 
I think in the general Lemaitre-Tolman-Bondi spacetimes you will find that the Ricci tensor is proportional to the density of the dust configuration, and therefore you can tune it to whatever you like. Give 'em a go with GRtensor =]

* C. W. Misner and D. H. Sharp. Relativistic equations for adiabatic, spherically
symmetric gravitational collapse. Phys. Rev., 136:B571, October 1964.

* S. Gon¸calves. Shell crossing in generalized Tolman-Bondi spacetimes. Phys. Rev. D,
63(12):124017, June 2001.
 

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