What kind of matter formed Primordial Blackholes?

[Mlesnita Daniel]

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

 

[Ibix]

I read somewhere

Where? Please provide a reference - it helps us to know what you know when we're answering.

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.

 

[Mlesnita Daniel]

I put the reference in an edit now, thanks for pointing out and thank you for clarifying!:)

 

[mathman]

The article should answer your questions.

 

[Ibix]

I agree with the OP that the article is misleadingly phrased. It says:

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.