I Discussing General Relativity - Beliefs & Ideas

Jamestein Newton
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Following are not strictly physics questions. But cool questions to discuss.
We need to add dark energy to our cosmological model if we strictly follow GR. This lead to some beliefs that GR is an effective theory.

(1)Do you believe that GR is the fundamental theory? If GR is an effective theory on some senses, what kind of fundamental physics can we take away from GR at the end?
(2)Do you think the gravitation would still be equivalent to the curvature of spacetime eventually? If not, what are the possible modifications? I am interested in the alternative description of gravitation that even only differ a bit from the current equivalent to the curvature of spacetime
(3)Do you think we need will modification on GR under the large scale?
(4)What will the main consequences of any possible modifications, and what will they lead to?

Just an informal chat. I am just curious about how people perceive GR nowadays.
 
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Jamestein Newton said:
Following are not strictly physics questions.
Indeed. Which means they are off topic here.

If you want to discuss particular proposals for theories that go beyond GR and have GR as an effective theory in a particular domain, those types of discussions would normally be in the Beyond the Standard Model forum and would be based on a particular valid reference (a published peer-reviewed paper that describes the proposed theory you want to discuss).

Some GR textbooks (such as MTW and Wald) also have discussions of how we might possibly go beyond GR. A PF discussion could also be based on what is said in those textbooks if you have questions about it.

In the meantime, this thread is closed.
 
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I asked a question here, probably over 15 years ago on entanglement and I appreciated the thoughtful answers I received back then. The intervening years haven't made me any more knowledgeable in physics, so forgive my naïveté ! If a have a piece of paper in an area of high gravity, lets say near a black hole, and I draw a triangle on this paper and 'measure' the angles of the triangle, will they add to 180 degrees? How about if I'm looking at this paper outside of the (reasonable)...
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...

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