dark matter question

[Genady]

Just now, hoola said:

is the galactic DM halo proposed to orbit along with the same speed and direction of the visible matter in our galaxy?

No, and observations show that it does not.

[DanMP]

On 1/6/2023 at 6:22 PM, swansont said:

On 1/6/2023 at 3:04 PM, DanMP said:

No, but nobody knows, so we can not rule out DM atmospheres

But you can blithely rule out higher energy DM? No, that’s not how this works.

Formulate a model where you form an atmosphere with DM, rather than declaring by fiat

I didn't say that DM atmospheres should exist, not even that "we can not rule out DM atmospheres" as you took it. I wrote:

On 1/6/2023 at 3:04 PM, DanMP said:

No, but nobody knows, so we can not rule out DM atmospheres just saying that neutrinos are not forming atmospheres.

I also wrote:

On 1/4/2023 at 3:46 PM, DanMP said:

Anyway, besides that we don't know exactly how DM atmospheres would/could form, we have some (observational?) evidence against them?

so I kind of admitted the lack of "a model where you form an atmosphere with DM". In your opinion, the temporarily lack of a model about how something was formed is enough to rule it out? How Higgs field (or any field) was formed? Do you have/know a model? How the conditions for big bang were "formed"?

By the way, do you have a model for "higher energy DM"? How/when the higher energy was acquired and why it doesn't decrease?

[swansont]

57 minutes ago, DanMP said:

I didn't say that DM atmospheres should exist, not even that "we can not rule out DM atmospheres" as you took it. I wrote:

Your original statement was “DM particles attracted by massive objects, like stars and planets, may form DM atmospheres around them?

If not, why not?”

Which sounds a lot like you think they should exist.

 

57 minutes ago, DanMP said:

I also wrote:

so I kind of admitted the lack of "a model where you form an atmosphere with DM". In your opinion, the temporarily lack of a model about how something was formed is enough to rule it out?

The mechanisms, other than gravity, involved in firming an atmosphere are absent. Genady and Janus both posted about this, too, and you responded.

 

57 minutes ago, DanMP said:

By the way, do you have a model for "higher energy DM"? How/when the higher energy was acquired and why it doesn't decrease?

Cold, warm and hot dark matter have all been hypothesized 

https://en.m.wikipedia.org/wiki/Warm_dark_matter

[hoola]

on my question of why the DM halo doesn't follow along with galactic matter......since there is a gravitational reaction between the two, why not? Shouldn't they eventually sync up in some form?

Edited January 9, 2023 by hoola

[Genady]

2 hours ago, hoola said:

on my question of why the DM halo doesn't follow along with galactic matter......since there is a gravitational reaction between the two, why not? Shouldn't they eventually sync up in some form?

This question refers to the rotation of a galaxy, right? Why would a gravitational interaction between DM halo and the galactic matter make DM halo to follow the rotation of galactic matter? Why would a gravitational force on DM in the direction of the galaxy rotation be larger than the gravitational force on DM in the opposite direction?

[swansont]

2 hours ago, hoola said:

on my question of why the DM halo doesn't follow along with galactic matter......since there is a gravitational reaction between the two, why not? Shouldn't they eventually sync up in some form?

The things that orbit in the disc have collisions. If you don’t, then what would make a particle orbit in that plane?

[hoola]

 frame dragging...could the collective mass of a galaxy exhibit a small potential for this, or at least at the vicinity of the central black hole? If DM particles have a non zero interaction, however small, wouldn't that offer a mechanism?

Edited January 11, 2023 by hoola

[Mordred]

Hint think of what a Galaxy comprises of prior to BH and stars.

[hoola]

gas

 

[Mordred]

Well let's replace gas with plasma. The same plasma used in star formation. Now that plasma is ionized so your dealing with a combination of rotation (conservation of angular momentum). Gravity and the EM field interactions. The EM field isn't involved for DM which is one of the distinctive differences in galaxy formation.

 When I get home I will find a decent article on how density wave theorem progresses but in essence the flattening into the plane is already underway with the above prior to the majority of star formation. Our galaxy for example has different star ages and also different metalicity percentages. This detail is covered in the density wave theorem.

[hoola]

near a rotating black hole and in the presence of DM, wouldn't a rotation of the proximate DM occur in the same direction of the bh due to frame dragging?

Edited January 13, 2023 by hoola

[hoola]

 about frame dragging...how extended from the event horizon is this effect predicted to occur?

[Mordred]

3 hours ago, hoola said:

 about frame dragging...how extended from the event horizon is this effect predicted to occur?

The frame dragging follows the same 1/r^2 relation as that of the Newtons gravitational law 

[hoola]

if the proximate dm has rotation matching the kerr bh frame dragging and extends that effect out at the 1/r^2 distance, and gravity effects being of infinite range, doesn't that infer a declining dm rotation rate extending into the galactic visible mass? 

Edited January 16, 2023 by hoola

[Mordred]

The gravity effect only has the potential to reach into infinite range if the mass is infinite. For a BH the range that the gravity has a measurable effect is what's involved. That can determined by the r^2 relation.

[hoola]

so....dm does rotate somewhat somewhere near the kerr hole, unless dm ignores space time, or is a minority variant species of space time itself.

Edited January 16, 2023 by hoola

[hoola]

Would a cavendish experiment in our galaxy's dm halo have a measure of G different from that measured on earth?

[Mordred]

No G would not be different. Yes DM would likely be affected by  Kerr metric frame dragging as it is affected by gravity just as any other particle. However it still won't clump in the same manner as baryonic matter due to lack of other field interactions such as the EM field.

[hoola]

so there would be some sympathetic rotation of the dm within a small finite range of the kerr bh event horizon, and would that range be larger with a smaller bh than of a bigger one?

Edited January 20, 2023 by hoola

[hoola]

does a smaller kerr bh have a more extensive frame dragging radius due to a higher gravitational gradient than of a larger one?

[Mordred]

It all depends on the mass of the BH. It isn't reliant on the gradient. I'm well aware your not strong on the mathematics so I won't try to post the ZAMO mathematics  (zero angular momentum observer) with regards to frame dragging.

 The details of such can be found here

https://www.roma1.infn.it/teongrav/onde19_20/kerr.pdf

Edited January 27, 2023 by Mordred