I When exactly did 'quantum fluctuations' in the early universe occur?

[MJM]

TL;DR Summary

A recent paper by Kawasaki and Murai discuss how quantum fluctuations could've led to primordial black holes, which eventually became the supermassive black holes we see today.

I came across this video today:

Which summarizes this new paper from University of Tokyo: https://arxiv.org/pdf/1907.02273.pdf

I get that the video is just an explainer for primordial black holes, but I was hoping to get a better explanation on exactly when conventional wisdom says density fluctuations occurred in the early universe. And what's the consensus on whether or not this can help explain dark matter?

 

[Mordred]

While I am unfamiliar with the AD field in this paper, which utilizes super symmetry (MSSM) in order to time with inflation estimates were looking at roughly $10^{-32}$ seconds.
No one knows what DM is for sure, however under MSSM treatments involving the Higgs field it's possible that DM may be sterile neutrinos which would form shortly after inflation with electro weak symmetry breaking (inflation itself may have be caused by EWSB) however this is just one theory among many.
Just a hunch but this reminds me of a type 2 seesaw mechanism involved in the paper. I would have to dig deeper to confirm that though

 

[Mordred]

Lol the reminder due to similarities of type 2 seesaw under MSSM Higgs/Higglets is about as far as that went ...
Glad I checked lmao

 

[Heikki Tuuri]

https://en.m.wikipedia.org/wiki/Primordial_black_hole

https://www.skyandtelescope.com/astronomy-news/black-holes/could-dark-matter-be-black-holes/

So far there is no evidence of such black holes existing, though the Sky and Telescope article above brings up one candidate.

The Wikipedia article lists observational bounds for the mass and the abundance of primordial black holes.

There is no obvious mechanism how the Big Bang would create mini black holes.

https://www.sciencemag.org/news/2017/02/dark-matter-made-black-holes

It looks like physicists do not believe that dark matter consists of black holes.