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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

by froeb 4y ago

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 4y ago
Here's some relevant background: https://physicsworld.com/a/cosmological-coupling-is-making-black-holes-bigger-study-suggests/ 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/10.3847/2041-8213/acb704 https://iopscience.iop.org/article/10.3847/1538-4357/acac2e 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 4y ago
  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 4y ago
    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.
    - AnIdiotOnTheNet 4y ago
      > 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.
    - anigbrowl 4y ago
      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.
    - bsder 4y ago
      > 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?
anigbrowl 4y ago
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.

by froeb 4y ago

ttpphd 4y ago

Here's some relevant background: https://physicsworld.com/a/cosmological-coupling-is-making-black-holes-bigger-study-suggests/ 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/10.3847/2041-8213/acb704 https://iopscience.iop.org/article/10.3847/1538-4357/acac2e 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 4y ago
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 4y ago
  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.
  - AnIdiotOnTheNet 4y ago
    > 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.
  - anigbrowl 4y ago
    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.
  - bsder 4y ago
    > 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?

anigbrowl 4y ago

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.