I How Do Inhomogeneities in Matter Affect Cosmic Evolution and Backreaction?

[Ranku]

It is being explored how the effect of inhomogenities in matter influence average cosmic evolution (Arxiv). Is there an equation of backreaction upon which such a possibility is being explored?

 

[PeterDonis]

Is there an equation of backreaction

What does the paper you referenced tell you?

 

[PeterDonis]

It is being explored how the effect of inhomogenities in matter influence average cosmic evolution (Arxiv).

This is really an "A" level topic, not an "I" level one. The only real "I" level answer that can be given is "it's complicated".

 

[Ranku]

What does the paper you referenced tell you?

It is an advanced-level critique of a rival paper, so doesn’t go much into the basics of backreaction.

 

[PeterDonis]

It is an advanced-level critique of a rival paper

What does the rival paper say? Or other references? The paper says references 1-8 are general reviews of the topic of backreaction.

 

[Ranku]

What does the rival paper say? Or other references? The paper says references 1-8 are general reviews of the topic of backreaction.

I’ve just come to know of the topic. So l’m looking for some basic information here.

 

[PeterDonis]

I’ve just come to know of the topic. So l’m looking for some basic information here.

As I said, this is an advanced topic, so even "basic information" probably requires graduate level background knowledge. I don't think "backreaction" can be boiled down to a single equation. Particularly not since there is still not general agreement about whether backreaction is even a significant effect in cosmology.

The best sources of general knowledge are probably the review articles referenced in the paper. It's possible that a recent cosmology textbook might have some discussion of it, but I have not seen one.

 

[Klystron]

Back when adults routinely wore hats outdoors, STEM teachers and authors used an expression "First find a place to hang your hat." when studying new concepts. IOW begin with material that you understand.

While reading the cited paper and following this discussion thread, I found a "place to hang my hat" in reference number 21] Abbott E A 1884 Flatland: A Romance of Many Dimensions. Curious why the authors referenced this classic Victorian mathematical satire, I followed the Abbott reference back through this paper's critique of the prior Green and Wald (GW) papers.

The common thread among this critique and GW papers describes how scientists measure and understand the topology of their universe, specifically in 'Sphereland' with 3+1 dimensions discussed in section 2 of your PDF. This paper discusses difficulties in proving relevance of backreaction inhomogeneities in cosmological theory without offering a primer on backreaction as a concept.

 

[Ranku]

Back when adults routinely wore hats outdoors, STEM teachers and authors used an expression "First find a place to hang your hat." when studying new concepts. IOW begin with material that you understand.

While reading the cited paper and following this discussion thread, I found a "place to hang my hat" in reference number 21] Abbott E A 1884 Flatland: A Romance of Many Dimensions. Curious why the authors referenced this classic Victorian mathematical satire, I followed the Abbott reference back through this paper's critique of the prior Green and Wald (GW) papers.

The common thread among this critique and GW papers describes how scientists measure and understand the topology of their universe, specifically in 'Sphereland' with 3+1 dimensions discussed in section 2 of your PDF. This paper discusses difficulties in proving relevance of backreaction inhomogeneities in cosmological theory without offering a primer on backreaction as a concept.

All I say to you is ‘May Your Tribe Increase’.

 

[phyzguy]

@Ranku I don't know what level of understanding you have, but I found this paper to help me understand the concept. The simulation run here seems to support the claim that backreaction may be significant.
https://arxiv.org/abs/1607.08797

 

[Ranku]

@Ranku I don't know what level of understanding you have, but I found this paper to help me understand the concept. The simulation run here seems to support the claim that backreaction may be significant.
https://arxiv.org/abs/1607.08797

Regardless of level of understanding, any relevant material is useful for improving understanding. Thanks for the reference link; it was informative.
Btw, what is ‘non-perturbative statistical estimation’? How is it different from ‘perturbative’?