Black Holes

[John Clark]

In the recent batch of Black Hole mergers that LIGO detected there is one called GW190412  2.4 billion light years away involving a 8 and a 31 solar mass Black Hole. This is the greatest difference in mass that LIGO has ever detected. If the two masses were the same the gravitational wave frequency would just be twice the orbital frequency because when they change positions by 180° the system would be the same, but because the masses were so different this asymmetry produced all sorts of interesting harmonics that exactly conformed to what Einstein predicted. It's never a good idea to bet against Einstein. It's worth noting that the smaller of the 2 Black Holes was spinning rapidly as you would expect if it was made from a collapsing star, but the larger one was spinning very slowly if at all. Theory predicts that if Primordial Black Holes exist then when they were first created, a time before there were atoms or even protons or neutrons, they would not be spinning at all, although they could pick up some spin later from infalling material.

GW190412: Observation of a Binary-Black-Hole Coalescence with Asymmetric Masses

John K Clark

[Lawrence Crowell]

This work was done by Kip Thorne and his group. Understanding the range of dynamics with black hole coalescence with asymmetric masses and angular momenta as been a long term phenomenological program. Working this complex perturbation theory with GR was something Kip pursued for 30 years This is complication applied math. 

It is hard to know whether there are primordial BHs. There must be bounds on them. for if there were a lot of them this would mean the early entropy of the universe would be too large.

LC 

[John Clark]

On Fri, Nov 6, 2020 at 6:16 AM Lawrence Crowell <goldenfield...@gmail.com> wrote:

> It is hard to know whether there are primordial BHs. There must be bounds on them. for if there were a lot of them this would mean the early entropy of the universe would be too large.

Too large for what?

 John K Clark 

[Lawrence Crowell]

If the entropy of the early universe were too large the current universe would be very different. In fact with black holes, if there were too many primordial BHs the universe would contain little other than BHs.

LC

[John Clark]

On Fri, Nov 6, 2020 at 10:58 AM Lawrence Crowell <goldenfield...@gmail.com> wrote:

> If the entropy of the early universe were too large the current universe would be very different. In fact with black holes, if there were too many primordial BHs the universe would contain little other than BHs.

Maybe to a first approximation the universe does contain very little matter except for primordial black holes if black holes turn out to be dark matter, or at least a substantial part of it. I'm not saying it's true I'm just saying it's possible.

 John K Clark

 

LC

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[Lawrence Crowell]

On Friday, November 6, 2020 at 1:40:16 PM UTC-6 johnk...@gmail.com wrote:

On Fri, Nov 6, 2020 at 10:58 AM Lawrence Crowell <goldenfield...@gmail.com> wrote:

> If the entropy of the early universe were too large the current universe would be very different. In fact with black holes, if there were too many primordial BHs the universe would contain little other than BHs.

Maybe to a first approximation the universe does contain very little matter except for primordial black holes if black holes turn out to be dark matter, or at least a substantial part of it. I'm not saying it's true I'm just saying it's possible.

 John K Clark

That has largely been ruled out. By looking for microlensing it appears dark matter is less than 1% due to primordial black holes.

LC 

LC

[John Clark]

On Fri, Nov 6, 2020 at 8:18 PM Lawrence Crowell <goldenfield...@gmail.com> wrote:

>>> If the entropy of the early universe were too large the current universe would be very different. In fact with black holes, if there were too many primordial BHs the universe would contain little other than BHs.

>> Maybe to a first approximation the universe does contain very little matter except for primordial black holes if black holes turn out to be dark matter, or at least a substantial part of it. I'm not saying it's true I'm just saying it's possible. John K Clark

> That has largely been ruled out. By looking for microlensing it appears dark matter is less than 1% due to primordial black holes.

I don't know if the idea is correct but I don't think it can be dismissed that easily, I don't think the evidence to support the conclusion that Primordial Black Holes being responsible for Dark Matter can be ruled out has been universally accepted as being sound. Evidence from microlensing against Black Holes being responsible for Dark Matter is strongest for them being greater than 100 solar masses, and the evidence from the cosmic microwave background radiation against them is strongest for Black Holes of less than 5 solar masses. It is precisely in that 5 to 100 solar mass gap that LIGO has found far more Black Holes than had been expected.  A recent paper  argues that the probability visible stars in a lensing galaxy could be responsible for all the observed microlensing is very small and concludes with:

" the most plausible candidates for the microlenses are primordial black holes, either in the dark matter halos of the lensing galaxies, or more generally distributed along the lines of sight to the quasars and the recent detection of gravitational waves attributed to a black hole merger supports this idea. It is possible that dark matter in the form of primordial black holes in the lensing galaxy halos are responsible for the observed microlensing, but it is not clear that they would constitute a sufficiently large optical depth to microlensing. A more plausible possibility is that the microlensing is the result of a cosmological distribution of dark matter primordial black holes along the line of sight to the quasar images."

The signature of primordial black holes in the dark matter halos of galaxies

Also, without Primordial Black Holes it is difficult to explain LIGO's discovery of a 66 and 85 solar mass Black Hole merger that occured 7 billion years ago because stars in that mass range can't produce them. Stars in the 65 to 135 solar mass range would end their lives in a Pair-instability Supernova, the most powerful type. The core of such stars would reach temperatures of about 300 million Celsius and the photons of light produced would be so energetic they would spontaneously convert into electrons and positrons which would reduce the radiation pressure and cause the core to collapse making it even hotter and instantly causing the fusion of every element in it that was lighter than Iron. This would completely blow the core apart leaving nothing behind, not a Neutron Star not a Black Hole nothing. Stars greater than 135 solar masses wouldn't produce a supernova at all, they would just collapse directly into a Black Hole and suddenly shut off, but stars that big are very rare, especially when you consider that they must've been in the 250 solar mass range when they started their lives because such stars give off huge amounts of matter as solar wind before they reach the end of their lives.

 

Primordial black hole dark matter and the LIGO/Virgo observations

And of course it could be that Primordial Black Holes make up part of Dark Matter and something completely unrelated makes up the other part, or the entire idea could just be wrong. Time will tell.  

John K Clark

[Lawrence Crowell]

On Saturday, November 7, 2020 at 6:27:34 AM UTC-6 johnk...@gmail.com wrote:

On Fri, Nov 6, 2020 at 8:18 PM Lawrence Crowell <goldenfield...@gmail.com> wrote:

>>> If the entropy of the early universe were too large the current universe would be very different. In fact with black holes, if there were too many primordial BHs the universe would contain little other than BHs.

>> Maybe to a first approximation the universe does contain very little matter except for primordial black holes if black holes turn out to be dark matter, or at least a substantial part of it. I'm not saying it's true I'm just saying it's possible. John K Clark

> That has largely been ruled out. By looking for microlensing it appears dark matter is less than 1% due to primordial black holes.

I will have to read this paper so as not to talk at cross purposes. It is a bit odd, for it appears to reference gravity lenses more than microlenses. Microlenses occur when a star "winks" because a gravity field passes in front of it. It is my understanding, which is not terribly deep in astronomical methods, that primordial BHs is now a minority report.

LC