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- Thread starter La Guinee
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General Relativity with a non zero cosmological constant is not compatible with special relativity in flat spacetimes or Newtonian gravity in the limit.

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Ok. But if a nonzero cosmological constant has an r^2 potential it can't be compatible with our universe either. How does one reconcile this with the fact that people think the cosmological constant isn't zero?General Relativity with a non zero cosmological constant is not compatible with special relativity in flat spacetimes or Newtonian gravity in the limit.

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How do you conclude as such?But if a nonzero cosmological constant has an r^2 potential it can't be compatible with our universe either.

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Wouldn't we have experimentally detected a potential that grows as r^2?How do you conclude as such?

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DrGreg

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Not if the constant of proportionality is exceedingly tiny!Wouldn't we have experimentally detected a potential that grows as r^2?

The effect of a tiny cosmological constant is only noticeable on huge (cosmological!) scales, and it's only in the last decade or so that we've found astronomical evidence to suggest it isn't zero.

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I don't see how that makes sense. No matter how small the cosmological constant is, I can find an r much much greater than the cosmological constant. Unless you're saying the cosmological constant is small even compared to the size of the universe.Not if the constant of proportionality is exceedingly tiny!

The effect of a tiny cosmological constant is only noticeable on huge (cosmological!) scales, and it's only in the last decade or so that we've found astronomical evidence to suggest it isn't zero.

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I take back what I just said. The condition would be that Lambda R^2 would have to be much less than 1, where R is the maximum distance over which Newtonian gravity has been observed to hold. Is this consistent with current estimates of the cosmological constant? In particular, the current upper bound would have to be less than or equal to the upper bound implied by this criterion. Anyone know if this is true?I don't see how that makes sense. No matter how small the cosmological constant is, I can find an r much much greater than the cosmological constant. Unless you're saying the cosmological constant is small even compared to the size of the universe.

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I found a paper that gives the estimate Lambda ~ 10^-52. That is indeed pretty small.

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