Can the Ricci Scalar Depend on Spacetime Coordinates?

  • Thread starter Thread starter div curl F= 0
  • Start date Start date
  • Tags Tags
    Ricci scalar Scalar
div curl F= 0
Messages
18
Reaction score
0
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
 
Physics news on Phys.org
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.
 
OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox. If black holes "evaporate" via Hawking radiation, then they cannot exist forever. So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon. Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon? The...
ASSUMPTIONS 1. Two identical clocks A and B in the same inertial frame are stationary relative to each other a fixed distance L apart. Time passes at the same rate for both. 2. Both clocks are able to send/receive light signals and to write/read the send/receive times into signals. 3. The speed of light is anisotropic. METHOD 1. At time t[A1] and time t[B1], clock A sends a light signal to clock B. The clock B time is unknown to A. 2. Clock B receives the signal from A at time t[B2] and...
From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...

Similar threads

Back
Top