Link between dark matter and baryonic matter

Hello!

I just read the work: https://arxiv.org/pdf/1609.05917v1.pdf
The authors conclusion: "The dark and baryonic mass are strongly coupled."

Only now they have noticed this?

8 years ago I came to the same conclusion. One can even read this ratio directly from rotation curves: they oscillate. Now, the authors speculate what may be the cause. And I have the explanation already ready

https://sites.google.com/site/testso...sh/dark-matter

"The dark matter is to be concentrated in the spiral arms. This contradicts the assumption that it consists from particles that surround the galaxy like a halo. On the other hand, this is strongly reminiscent of the asteroid belt in our solar system or rings around Saturn and Jupiter. Therefore, it may act on dark matter around small cosmic bodies, such as rocks, asteroids, planets, comets, and snowballs. They are small to be seen from a distance, but in principle they can make up the bulk of our galaxy and other galaxies."

Or see he https://groups.google.com/d/msg/sci....k/be691fU5sxIJ

Best regards

Walter Orlov

On 9/28/2016 5:54 AM, wrote:
Hello!

I just read the work: https://arxiv.org/pdf/1609.05917v1.pdf
The authors conclusion: "The dark and baryonic mass are strongly coupled."

Only now they have noticed this?

It sounds like they are rediscovering MOND.

Yousuf Khan

Am Mittwoch, 28. September 2016 15:04:56 UTC+2 schrieb Yousuf Khan:

It sounds like they are rediscovering MOND.


If one definitely want a new physics, then comes into question only the old MOND

Dear wor...:

On Wednesday, September 28, 2016 at 2:54:40 AM UTC-7, wrote:
Hello!

I just read the work: https://arxiv.org/pdf/1609.05917v1.pdf
The authors conclusion: "The dark and baryonic mass
are strongly coupled."

Only now they have noticed this?

Actually there are papers at the same source, that agree that all Dark Matter could be normal, baryonic matter, but it creates the problem of evaluating "by some other means" the amount of matter near the rim, since luminosity drops off so quickly (due to dust, etc.).

Recall that "Dark" originated from establishing a mass / luminosity ratio at the center of a spiral galaxy. We have since found out what a special place that location is, as compared to elsewhere in a spiral's disc... no significant dust, stars without much in the way of a photosphere (due to tidal effects), and likely very few planets of any size.

Since we no longer rely on mass / luminosity, but can in most cases verify rotation curves with microlensing (at least locally), we no longer need to use failed methods.

Neither MOND nor exotic matter are *required*, nor do they show up in our own solar system. So we are NOT in a special place after all.

If we are into opinions here...

David A. Smith

On 9/28/2016 10:54 AM, dlzc wrote:
Actually there are papers at the same source, that agree that all Dark Matter could be normal, baryonic matter, but it creates the problem of evaluating "by some other means" the amount of matter near the rim, since luminosity drops off so quickly (due to dust, etc.).

Recall that "Dark" originated from establishing a mass / luminosity ratio at the center of a spiral galaxy. We have since found out what a special place that location is, as compared to elsewhere in a spiral's disc... no significant dust, stars without much in the way of a photosphere (due to tidal effects), and likely very few planets of any size.

Since we no longer rely on mass / luminosity, but can in most cases verify rotation curves with microlensing (at least locally), we no longer need to use failed methods.

Neither MOND nor exotic matter are *required*, nor do they show up in our own solar system. So we are NOT in a special place after all.

If we are into opinions here...

Maybe the issue here is not to find a new modification of Newtonian
gravity, but perhaps our reliance on still using Newtonian gravity even
100 years after we found a better theory of gravity might be the problem
here? We're still using Newtonian gravity after all of these years,
because it's frankly much easier to calculate with than General
Relativity. And we're still confidant in its validity, because we
imagine that it is "still good enough". GR isn't calculating
easy-to-understand force-distance relationships, instead it's
calculating curvatures in spacetime. But in a many-body system such as
stars in a galaxy or galaxies in a universe, those simple
inverse-distance squared relationships simply don't work out anymore?

We're still using Newtonian gravity in this day and age because we still
don't have computers strong enough to do a GR calculation for an entire
galaxy. Using even our strongest supercomputers we can do perhaps a
simulation of only a few million stars in a galaxy using GR, but our
galaxy contains perhaps as much as 400 billion stars, so we keep
approximating with Newton. If one day we can do a full simulation of the
Milky Way with all of its entire 400 billion stars, then likely we'll
see surprising results coming out of GR that are inconsistent with
Newton, and then we'll be finally shaken of our illusion that Newton is
"still good enough".

Yousuf Khan

Dear Yousuf Khan:

On Saturday, October 15, 2016 at 10:45:21 PM UTC-7, Yousuf Khan wrote:
....
Maybe the issue here is not to find a new
modification of Newtonian gravity, but perhaps
our reliance on still using Newtonian gravity
even 100 years after we found a better theory
of gravity might be the problem here?

I find it more likely that a nearly 100 year old assumption that luminosity is directly proportional to the amount of mass present, when it has long been known that luminosity drops off rapidly with surface temperature. If you have cooler objects, they simply don't put out as much light... especially in the visible light bands.

We're still using Newtonian gravity after all
of these years, because it's frankly much easier
to calculate with than General Relativity.

Paper on this subject for a "simple" galaxy, and evaluating the possible error between Newtonian gravity-as-a-force and GR, and in that galaxy, it is a 1% (or so) error, not the necessary 300% error.

But in a many-body system such as stars in a
galaxy or galaxies in a universe, those simple
inverse-distance squared relationships simply
don't work out anymore?

They do work out "well enough", for simple gravitation.

But we are "blind as bats" at these scales, and have a full complement of "flatlander fallacies" that we have to divest ourselves of.

We're still using Newtonian gravity in this day
and age because we still don't have computers
strong enough to do a GR calculation for an
entire galaxy.

False. The amount of computer time might still be abysmally long for an interesting galaxy, but it would still be doable. After all, Nature does this math in real time...

Using even our strongest supercomputers we can
do perhaps a simulation of only a few million
stars in a galaxy using GR, but our galaxy contains
perhaps as much as 400 billion stars, so we keep
approximating with Newton.

Yet, even small spirals show a need for Dark Matter. Globular clusters, essentially don't.

If one day we can do a full simulation of the
Milky Way with all of its entire 400 billion stars,
then likely we'll see surprising results coming out
of GR that are inconsistent with Newton, and then
we'll be finally shaken of our illusion that Newton
is "still good enough".

Maybe. But the speeds and curvature on something the size of a galaxy, even the Milky Way, should present minimal error in using Newton.

Now what I wonder is, if the "perfectly mirrored, massless box, containing photons", which has rest mass, exists between a star and the gases/dust/planets that give that star a background temperature higher than the CMBR. So some Dark Matter (probably less than 1%) might still be photons in transit between intersystem objects...?

David A. Smith

In article ,
Yousuf Khan writes:
We're still using Newtonian gravity in this day and age because we still
don't have computers strong enough to do a GR calculation for an entire
galaxy.

That's not the problem. GR is mathematically identical to Newtonian
gravity provided gravity is not "strong" and speeds are "low"
compared to the speed of light. The magnitude of the errors can be
quantified for the actual gravitational potentials and speeds in any
particular calculation.

The real problems are 1) even Newtonian gravity is too hard to
calculate when the system has too many bodies, and 2) treating stars
and gas together in a single calculation is difficult. These
problems require approximations to be made, and in some cases these
approximations may be inaccurate enough to affect results. That's
not to say every calculation ever done is hopelessly wrong, but any
result that depends critically on what happens when two stars come
very close together is uncertain.

People who do these calculations are well aware of the uncertainties,
but those seldom get transmitted in popular articles.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

In article ,
dlzc writes:
I find it more likely that a nearly 100 year old assumption that
luminosity= is directly proportional to the amount of mass
present, when it has long b= een known that luminosity drops off
rapidly with surface temperature.

As you say, the dependence of luminosity on temperature -- more
generally on stellar population -- is well known. It is taken into
account as well as possible given the data available, and the
resulting uncertainties are understood.

If y= ou have cooler objects, they simply don't put out as much
light... especially in the visible light bands.

As you indicate, working in the infrared helps quite a bit. It
doesn't eliminate the uncertainties altogether, though.

Now what I wonder is, if the "perfectly mirrored, massless box,
containing = photons", which has rest mass, exists between a star

Photons have energy, which contributes to gravitation, but they don't
have rest mass.

and the gases/dust/pla= nets that give that star a background
temperature higher than the CMBR. So= some Dark Matter (probably
less than 1%) might still be photons in transit= between
intersystem objects...?

Light has to be considered separately from matter in the cosmological
equations because its energy density decreases as the fourth power of
scale factor. The energy density of light has been less than that of
matter since the first several minutes of cosmic time, and its energy
density is negligible at later epochs.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

Dear Steve Willner:

On Wednesday, October 19, 2016 at 12:15:35 PM UTC-7, Steve Willner wrote:
In article ,
dlzc writes:
....
Now what I wonder is, if the "perfectly mirrored, massless box,
containing = photons", which has rest mass, exists between a star

Photons have energy, which contributes to gravitation, but
they don't have rest mass.

Individually, no. But in groups, with a center of momentum frame, they do have rest mass. And hence gravitational mass.

and the gases/dust/pla= nets that give that star a background
temperature higher than the CMBR. So= some Dark Matter (probably
less than 1%) might still be photons in transit= between
intersystem objects...?

Light has to be considered separately from matter in the
cosmological equations because its energy density decreases
as the fourth power of scale factor. The energy density of
light has been less than that of matter since the first several
minutes of cosmic time, and its energy density is negligible at
later epochs.

As I said, I did not expect it to be even 1%, much less what is required to be Dark Matter.

Thank you.

David A. Smith

On 10/16/2016 1:05 PM, dlzc wrote:
Dear Yousuf Khan:

On Saturday, October 15, 2016 at 10:45:21 PM UTC-7, Yousuf Khan
wrote: ...
Maybe the issue here is not to find a new modification of
Newtonian gravity, but perhaps our reliance on still using
Newtonian gravity even 100 years after we found a better theory of
gravity might be the problem here?

I find it more likely that a nearly 100 year old assumption that
luminosity is directly proportional to the amount of mass present,
when it has long been known that luminosity drops off rapidly with
surface temperature. If you have cooler objects, they simply don't
put out as much light... especially in the visible light bands.

But they do still glow in the cooler invisible light bands like IR and
microwave and radio.

We're still using Newtonian gravity after all of these years,
because it's frankly much easier to calculate with than General
Relativity.

Paper on this subject for a "simple" galaxy, and evaluating the
possible error between Newtonian gravity-as-a-force and GR, and in
that galaxy, it is a 1% (or so) error, not the necessary 300% error.

That's the point I'm trying to make, they are using "simple" galaxy
models, rather than full galaxy models.

But in a many-body system such as stars in a galaxy or galaxies in
a universe, those simple inverse-distance squared relationships
simply don't work out anymore?

They do work out "well enough", for simple gravitation.

But we are "blind as bats" at these scales, and have a full
complement of "flatlander fallacies" that we have to divest
ourselves of.

So then we're basically agreeing on this. Newtonian gravity might be one
of those flatlander fallacies.

We're still using Newtonian gravity in this day and age because we
still don't have computers strong enough to do a GR calculation
for an entire galaxy.

False. The amount of computer time might still be abysmally long
for an interesting galaxy, but it would still be doable. After all,
Nature does this math in real time...

Nature has its own entire universe-sized quantum computer to work with.
We can barely put two qubits together yet.

Using even our strongest supercomputers we can do perhaps a
simulation of only a few million stars in a galaxy using GR, but
our galaxy contains perhaps as much as 400 billion stars, so we
keep approximating with Newton.

Yet, even small spirals show a need for Dark Matter. Globular
clusters, essentially don't.

Then we need to investigate where the globular clusters differ from
dwarf galaxies.

If one day we can do a full simulation of the Milky Way with all
of its entire 400 billion stars, then likely we'll see surprising
results coming out of GR that are inconsistent with Newton, and
then we'll be finally shaken of our illusion that Newton is "still
good enough".

Maybe. But the speeds and curvature on something the size of a
galaxy, even the Milky Way, should present minimal error in using
Newton.

Well, that's been our assumption all along hasn't it? Maybe our
assumption is wrong?

Now what I wonder is, if the "perfectly mirrored, massless box,
containing photons", which has rest mass, exists between a star and
the gases/dust/planets that give that star a background temperature
higher than the CMBR. So some Dark Matter (probably less than 1%)
might still be photons in transit between intersystem objects...?

Or even neutrinos.

Yousuf Khan