What kind of matter formed Primordial Blackholes?

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Discussion Overview

The discussion revolves around the formation of primordial black holes (PBHs) and the nature of the matter involved in their creation. Participants explore the implications of density variations in the early universe and how these might lead to the collapse of matter into black holes, as well as the phrasing used in a referenced article.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether "space itself" could collapse into PBHs or if it is the denser matter within space that collapsed to form them.
  • Another participant clarifies that the concept of "space itself" is not meaningful in general relativity and emphasizes that variations in matter density could lead to black hole formation.
  • A participant critiques the phrasing in the referenced article, suggesting it misleadingly implies that space collapses rather than the matter within it.
  • There is a discussion about the distinction between non-homogeneous space and non-homogeneous matter, noting that while related, they are not the same.
  • One participant suggests that the article may have avoided using the term "matter" to describe the early universe's contents, which included components that eventually formed matter and radiation.

Areas of Agreement / Disagreement

Participants express differing views on the clarity of the article's phrasing and the implications of density variations in the early universe. There is no consensus on the interpretation of the article or the nature of the collapse leading to PBHs.

Contextual Notes

Participants highlight the complexity of the concepts involved, including the relationship between space and matter in the context of general relativity, and the potential ambiguity in terminology used in popular science articles.

Mlesnita Daniel
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I read somewhere "space was not completely homogenous (the same at every point). Instead, some areas were denser and hotter than others, and these dense regions could have collapsed into black holes." and I was wondering what does it exactly means?

Did space itself fall into becoming PBHs (primordial black holes) or it means that the matter that WAS IN space was denser and it collapsed to form such objects?

Thank you!

Edit: Where I read it: https://astronomy.com/news/2019/07/primordial-black-holes
 
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Mlesnita Daniel said:
I read somewhere
Where? Please provide a reference - it helps us to know what you know when we're answering.

Mlesnita Daniel said:
Did space itself fall into becoming PBHs (primordial black holes) or it means that the matter that WAS IN space was denser and it collapsed to form such objects
The matter. "Space itself" isn't really a concept that makes sense in general relativity. The density of matter in the early universe wasn't completely uniform, and if it varied enough it's possible that the densest bits collapsed to form black holes. I don't believe that the signatures of such things have been detected, but I don't think they are ruled out.
 
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I put the reference in an edit now, thanks for pointing out and thank you for clarifying!:)
 
The article should answer your questions.
 
I agree with the OP that the article is misleadingly phrased. It says:
astronomy.com said:
in that fraction of a second after the universe itself began, space was not completely homogenous (the same at every point). Instead, some areas were denser and hotter than others, and these dense regions could have collapsed into black holes.
That does read (incorrectly) like space is collapsing to form black holes. This part isn't making a clear distinction between space being non-homogeneous (true, with a certain amount of glossing over complicated topics) and the matter in space being non-homogeneous (also true). The two facts are inextricably related, but aren't exactly the same statement.

Maybe they were trying to avoid saying "matter"? It wasn't matter in the colloquial sense of a bunch of atoms. But it was the stuff that eventually cooled down (the bits of it that didn't fall into these hypothetical primordial black holes, anyway) to form matter and radiation as we see it today.
 

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