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 ...
user avatar
  • 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 ...
user avatar
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 ...
user avatar
  • 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(\...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 ...
user avatar
  • 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 $\nabla \cdot {\bf E}=0$ ...
user avatar

Only top scored, non community-wiki answers of a minimum length are eligible