Dark energy from supermassive black holes? Physicists spar over radical idea

Most of that has been ruled out (see the graph on http://resonaances.blogspot.com/2016/06/black-hole-dark-matt... ) and while some black holes may fall into the dark matter category, the observed "if there were that many black holes, micro lensing would be this common..."

The result of those tests constrains black holes to less than 1% of the calculated dark matter... though there are some windows where there is very likely active research to try to detect black holes with those masses along with the cosmological models needed to have an early universe that produces black holes of that size in that quantity.

From https://arxiv.org/pdf/2007.10722v3.pdf

> Primordial Black Holes, in particular asteroid mass ones, remain a viable dark matter candidate. Further improve- ments in the theoretical calculations of the production and evolution of PBHs are required to reliably predict the abundance and properties of PBHs from a given model. Even so, it seems clear that a cosmologically interesting num- ber of PBHs can only be produced in specific models of the early Universe, and often fine-tuning is required. However, whether or not PBHs are a significant component of the DM is a question that has to be answered observationally. Novel ideas are needed here to either detect or rule out the remaining open parameter space.

Note that we're dealing with really small ones that haven't evaporated yet.

The chart on page 16 - with M PBH [g] and the X axis of 10^15 to 10^36 - that's grams.

Also fun - https://github.com/bradkav/PBHbounds which has them in solar masses

In particular, dark energy is not

> "the cause of the difference between what is calculated, and what is observed"

Dark energy / the cosmological constant Λ is a completely natural parameter to the field equations, not a corrective term (even though it might feel that way if you follow the history of cosmology). It's not that we calculated Λ to be zero but observations forced us to set it to something non-zero. We had no clue what it's value should be and simply deduced from observations that it happens to be non-zero. End of story.

Now, particle physicists / field theorists have been looking for a particle physics-based explanation for Λ and preliminarily called it "dark energy". But there's no guarantee there is one. Maybe Λ is indeed just a boring parameter.

[chatGPT]> There is currently no evidence to suggest that dark energy can be compressed into a small volume and exhibit a gravitational pull in the same way that ordinary matter does. Dark energy is thought to be a property of the vacuum of space itself, and its effect on the universe is driven by its negative pressure, which causes the universe's expansion to accelerate.

Black hole masses are measured by observing their gravitational effects on surrounding matter and other astronomical objects. The mass of a black hole can be estimated by measuring the velocity of nearby stars or gas clouds and using the laws of gravity to infer the mass of the object producing the gravitational field. These measurements are based on our current understanding of gravity and are not affected by the presence or absence of dark energy.

However, it is worth noting that the properties of dark energy are still not fully understood, and there may be some new discoveries or developments in our understanding of gravity that could change our current understanding of these phenomena. Nonetheless, as of now, there is no evidence to suggest that dark energy can contribute to our measurements of black hole masses through its gravitational effects.