3
votes
Accepted
How does the scale of a cataclysm determine if we can look beyond it?
Cataclysmicity is not a physically measurable observable. That part of the quote is not physics. The first sentence should refer to the theories of cosmology, plural possessive. Cosmology is a branch ...
- 8,633
2
votes
Writing the metric of 4D de Sitter space as a 5D metric
What you want is the induced metric. I am not going to solve this explicitly for you since this is a very standard homework/exam exercise. But let me sketch the identical computation for a sphere.
A ...
2
votes
Are there any CMB-independent probes of the curvature of the Universe?
Supernovae measurements provide constraints on $\Omega_k$ independent of CMB measurements. A relatively up to date example of this are the constraints from the Pantheon supernovae sample, detail in ...
- 1,095
2
votes
Cosmology context - MCMC code : Recomputation of covariance matrix after each point accepted
I am having trouble interpreting exactly what you are asking, but I will answer based on my understanding of your question.
In the Metropolis-Hastings algorithm, you have a generating function $g(\...
- 1,095
1
vote
Is this right that the fate of space expansion depends on matter density inside the universe?
General relativity is the theory of how matter affects space (tells it how to bend) and space affects matter (tells it how to move). The equations governing the expansion of the Universe are derived ...
- 4,432
1
vote
Matter-antimatter annihilation and CMBR
Sort of. The CMB are photons we detect from the last scattering surface, essentially when the universe went from being opaque to transparent (approximately at around $3000K$). The opaqueness was just ...
- 2,849
1
vote
Cosmological constant divergence
The cosmological constant contributes to our universe's energy density, so it curves spacetime. The answer to #2 and #3 is therefore "yes".
As for #1, if the cosmological constant is ...
- 16.4k
1
vote
What is the Ricci curvature tensor in a region of sparse matter?
I suggest as a way in you first consider the simpler case of electromagnetism, and then take the case you asked about.
For electromagnetism you could, for example, note that $\nabla \cdot {\bf E}=0$ ...
- 46.2k
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