[HN Gopher] Scientists find first evidence that black holes are ...
___________________________________________________________________
Scientists find first evidence that black holes are the source of
dark energy
Author : qwertyuiop_
Score : 24 points
Date : 2023-02-15 18:09 UTC (4 hours ago)
(HTM) web link (www.imperial.ac.uk)
(TXT) w3m dump (www.imperial.ac.uk)
| froeb wrote:
| This is a pretty confusing article. I think the conventional
| understanding is that dark energy is associated with empty space
| itself. Is this article discussing a proposed mechanism for dark
| energy, or an alternate explanation altogether? What is
| cosmological coupling, is that new physics or an emergent
| phenomenon from more realistic black hole solutions?
| ttpphd wrote:
| Here's some relevant background:
| https://physicsworld.com/a/cosmological-coupling-is-making-b...
|
| And the two papers mentioned in the OP:
|
| https://iopscience.iop.org/article/10.3847/2041-8213/acb704
|
| https://iopscience.iop.org/article/10.3847/1538-4357/acac2e
|
| I extracted a summary using a large language model.
|
| The two papers are related and explore the growth of
| supermassive black holes (SMBHs) in elliptical galaxies over
| cosmic time. The first paper, published in The Astrophysical
| Journal, focuses on the assembly of SMBH and stellar mass in
| elliptical galaxies and their relative positions on the M BH-M
| * plane, where M BH is the SMBH mass and M * is the stellar
| mass. The authors construct three samples of elliptical
| galaxies, one at z ~ 0 and two at 0.7 [?] z [?] 2.5, and find
| evidence for translational offsets in both stellar mass and
| SMBH mass between the local sample and both higher-redshift
| samples. The offsets in stellar mass are small and consistent
| with measurement bias, but the offsets in SMBH mass are much
| larger, reaching a factor of 7 between z ~ 1 and z ~ 0. The
| result is robust against variation in the high- and low-
| redshift samples and changes in the analysis approach. The
| magnitude and redshift evolution of the offset are challenging
| to explain in terms of selection and measurement biases. The
| authors conclude that either there is a physical mechanism that
| preferentially grows SMBHs in elliptical galaxies at z [?] 2,
| or that selection and measurement biases are both
| underestimated, and depend on redshift.
|
| The second paper, published in The Astrophysical Journal
| Letters, explores the implications of cosmological coupling for
| the growth of black holes and the origin of dark energy. The
| authors consider the growth of SMBHs in elliptical galaxies
| over 0 < z [?] 2.5 and find evidence for cosmologically coupled
| mass growth among these black holes, with zero cosmological
| coupling excluded at 99.98% confidence. Cosmological coupling
| refers to the idea that the mass of a black hole can increase
| with the expansion of the universe, independently of accretion
| or mergers, in a manner that depends on the black hole's
| interior solution. The redshift dependence of the mass growth
| implies that, at z [?] 7, black holes contribute an effectively
| constant cosmological energy density to Friedmann's equations.
| The continuity equation then requires that black holes
| contribute cosmologically as vacuum energy. The authors propose
| that stellar remnant black holes are the astrophysical origin
| of dark energy, explaining the onset of accelerating expansion
| at z ~ 0.7.
|
| Taken together, the two papers suggest that there is a physical
| mechanism that preferentially grows SMBHs in elliptical
| galaxies at z [?] 2, and that the growth of black holes is
| cosmologically coupled, which could have implications for the
| origin of dark energy. The idea of cosmological coupling is
| important because it implies that black holes can contribute to
| the energy density of the universe in a way that is not
| dependent on accretion or mergers, and that the growth of black
| holes is not isolated from the expansion of the universe. This
| means that black holes could be a potential source of dark
| energy, which is the mysterious force that is causing the
| accelerated expansion of the universe.
| anigbrowl wrote:
| _I extracted a summary using a large language model._
|
| Please do not. While that is an interesting educational tool
| that I like to use too, republishing it is just information
| pollution because it will create unproductive feedback loops.
| We always have abstracts to fulfill this need.
| dilippkumar wrote:
| Hard disagree. GP comment was extremely useful to me, and I
| want this usage to continue.
|
| > republishing it is just information pollution because it
| will create unproductive feedback loops.
|
| Internet forums have never been grounded in epistemic
| rigor. If feedback loops have to be avoided, that
| responsibility does not fall on everyday users of the
| internet.
|
| Find better sources to train models.
| anigbrowl wrote:
| This is what the abstract is for, or you can submit
| material to an LLM on your own, or read any of many
| explainer articles by people with varying degrees of
| scientific knowledge and professional writing ability.
| AnIdiotOnTheNet wrote:
| > Hard disagree. GP comment was extremely useful to me,
| and I want this usage to continue.
|
| If I told you everything it said was nonsensical and not
| at all what is reflected by the papers, would you still
| think it was useful?
|
| I'm not a physicist of any stripe, so I actually have no
| idea about the accuracy, but I'm not willing to believe a
| bullshit generator just because it sounds convincing.
| bsder wrote:
| > Hard disagree. GP comment was extremely useful to me,
| and I want this usage to continue.
|
| And why do you believe that comment to be _correct_ in
| any way shape or form?
|
| Does it _actually_ reflect the article? Did it get
| something subtly wrong? Or maybe it 's completely wrong?
|
| You'll have to pull up the article to answer those
| questions _anyway_ , so why add this noise?
| ttpphd wrote:
| My only reaction is extreme amusement. The idea that there
| is some sacred collection of words we must keep pure is
| funny.
| anigbrowl wrote:
| If that was your takeaway then I did a bad job of
| communicating, because that was not the idea at all.
| ThrowawayR2 wrote:
| dang has indicated that machine generated content is not
| welcome on HN: " _HN has never allowed bots or generated
| responses. If we have to, we 'll add that explicitly to
| https://news.ycombinator.com/newsguidelines.html, but I'd
| say it already follows from the rules that are in
| there._" The full post is at
| https://news.ycombinator.com/item?id=33950747
| ttpphd wrote:
| Not breaking any of those rules, but it could be argued
| that y'all are breaking the one about tangential
| annoyances.
|
| My comment was good. It provided primary source material
| and supplementary background material, then provided a
| clearly and explicitly marked summary of the content.
| anigbrowl wrote:
| My takeaway from the summary article (not having looked at the
| underlying papers yet, and being unable to properly evaluate
| their claims anyway), is that they've found a sufficiently good
| correlation between data on black holes and expansion to say
| likely related and that Einstein's cosmological constant
| hypothesis was basically correct.
|
| If validated this could be quite significant because physicists
| (starting with Einstein himself) had basically thrown the idea
| out until 25 years ago and spent most of their energy on
| looking for a better theory. Being able to treat CC as a fact
| would probably open up new horizons of both theory and
| technology. My understanding is that the biggest theoretical
| consequence of an ever-accelerating expansion is that
| eventually spacetime itself disappears in an event known as
| 'the big rip' in which everything down tot he atomic level
| flies apart, as opposed to the big crunch in which everything
| smushes together.
|
| In conclusion, we need to invest billions in new
| instrumentation to give us answers to questions that are too
| abstract to have any foreseeable practical implications, unless
| you want to deal with a small army of very determined nerds
| that might otherwise turn their attention to building
| 'interesting' new weapons.
| westurner wrote:
| Is there a different understanding of dark energy given a theory
| of Superfluid Quantum Gravity?
| Smar wrote:
| Maybe just change the title to "Yet another article with title
| contradicting the content".
| froeb wrote:
| I took some time to skim the original paper and learned about
| cosmological coupling for the first time! My understanding is
| that black hole solutions in an expanding spacetime have way more
| freedom than the regular Kerr solution, because Birkhoff's
| theorem doesn't apply anymore. This means you can get time
| varying black hole solutions, one of which involves "cosmological
| coupling" where the mass of the black hole increases with the
| expansion of the universe.
|
| I think this is just a possibility allowed by GR though, I think
| you would need a theory of quantum gravity to say whether such
| "cosmologically coupled" mass actually exists in a black hole.
|
| I suppose this research group is claiming to have experimental
| evidence of it though? That is very interesting if true.
|
| Also, I am not sure how you go from cosmological coupling to
| saying that black holes are the "source" of dark energy. I need
| to read further
| apienx wrote:
| I got very excited reading that title but it's just a
| misrepresentation of the actual study. There's nothing in the
| paper that can be considered "evidence".
|
| Still...exciting stuff!
___________________________________________________________________
(page generated 2023-02-15 23:02 UTC)