Very helpful. So for primordial objects, it sounds like we'd be looking for
flashes in an otherwise/almost ambient field, as opposed to distortions of an
otherwise steady/bright object. If we find too few (scaling up however for
estimates of the unobserved), then it's evidence against. What I was wondering
was more around the sizes. The primordial ones must be smaller, I'd guess. But
they'd have to be everywhere at first (most distant), then clumping together
over time (closer). And I can't help but wonder if the anisotropic clumping
could explain those puffy galaxies light on dark matter.
I can't muster empathy to the disappointment in reconciling the particles with
gravity, though. 8^D I'm too much of an outsider, I guess ... like the new
marketing suit touring the server room having no idea what he's looking at but
marveling at the cables, and the hum, and the Morlocks tapping away. The
pictures on 7/12 are guaranteed to be pretty, regardless of what they mean.
On 6/27/22 13:29, David Eric Smith wrote:
What a great shot in the arm to start a morning.
I just got back from a small conference in Groningen, which turns out to be (I
didn’t know) a kind of fountainhead for large-scale structure cosmologists. So
got some much-needed remedial education on the topics in Glen’s links below.
I asked one guy what was the bound on how many black holes could have been
produced early, given what we know today, thinking (in my near-total ignorance)
that it would be collisions reported with the LIGO et al. collaboration. His
answer mentioned something I didn’t see in these articles, which was that
microlensing counts are likely to provide some of the best bounds on the
primordial black holes if they are to be dark matter candidates. This is when
a telescope is looking at some distant dim dot, and it briefly flickers
brighter because a black hole passed between it and us, and lensed in a tiny
bit more angular sector of its light. I guess Webb contributes to those counts
too (if I didn’t create a further mis-understanding).
The idea that all of dark matter could be accounted for with nothing but black
holes is strangely both tempting and disappointing. Tempting in that, in the
short term, it would explain a phenomenon, and check one more off the list.
Disappointing in that, if we could close _everything_ we can observe with just
the low-energy standard model and general relativity, then we have no clues
what to do to make them consistent. If there were at least some phenomena that
we could show were _sure_ to be beyond explanation with the existing models, we
could at least hang a hope on there's being some signature to lead into this
very deep high-energy wilderness that, for now and maybe indefinitely, we can’t
reach in any lab on Earth.
Good stuff,
Eric
On Jun 27, 2022, at 11:39 PM, glen <geprope...@gmail.com> wrote:
I'm guessing "primordial" carries the foundationalist urge, whereas "primeval" is more
agnostic to foundations, but targets sequence. So the test for hypothesis is simply *if* Webb finds no
evidence of small black holes, then the they can't account for dark matter. Right? Or is there something more
subtle about it? ... mabye something "distributional"?
Black holes and dark matter — are they one and the same?
https://news.yale.edu/2021/12/16/black-holes-and-dark-matter-are-they-one-and-same
Webb’s Quest for Primeval Black Holes
https://blogs.nasa.gov/webb/2022/05/26/webbs-quest-for-primeval-black-holes/
And maybe tangentially,
Astronomers identify likely location of medium-sized black holes
https://phys.org/news/2022-04-astronomers-medium-sized-black-holes.html
P.S. July 12th:
First Images of the James Webb Space Telescope (Official NASA Broadcast)
https://youtu.be/nmMRMIE3MGw
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