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Can dark matter be small objects?



 
 
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  #1  
Old April 18th 15, 04:19 AM posted to sci.astro.research
Ray Tomes[_3_]
external usenet poster
 
Posts: 2
Default Can dark matter be small objects?

Gas and dust is able to be detected by its effect on light. Large
objects glow from their own light. If intermediate objects were at
low temperature would they generally be detectable? There are many
orders of magnitude between dust and the dimmest starts. How many
of these could definitely not contribute to dark matter and why?

[[Mod. note -- It's almost impossible to say that something does
"definitely not contribute"; usually "all" we can do is put upper
limits on any possible contribution. Gravitational-lensing observations
are often used to place such limits, and we've discussed them numerous
times in this newsgroups.
-- jt]]
  #2  
Old April 20th 15, 05:24 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default Can dark matter be small objects?

In article , Ray
Tomes writes:

Gas and dust is able to be detected by its effect on light. Large
objects glow from their own light. If intermediate objects were at
low temperature would they generally be detectable? There are many
orders of magnitude between dust and the dimmest starts. How many
of these could definitely not contribute to dark matter and why?


"Dark matter" is a bit of a misnomer. What most people mean these days
is "some sort of non-baryonic matter, other than neutrinos, which we
have not yet detected". This is the "DM" in, e.g., "LambdaCDM". Other
things can be dark, such as cold gas, dust, and so on. However, we have
good upper (and lower) limits on baryons from big-bang nucleosynthesis,
so while there are some dark baryons, they cannot be an appreciable
fraction of the dark matter.

It's also a bit of a misnomer since "dark" here means that it does not
interact electromagnetically. Yes, that means it doesn't glow, but it
also means that it doesn't reflect or absorb light. In other words, it
is transparent. At most it is weakly interacting (i.e. via the weak
"nuclear" force), but this is not something which can be investigated
astrophysically, so only gravitational effects are left. (Since we
don't know what it is, we don't know if it is self-interacting and hence
don't know if it can form macroscopic objects.)
  #3  
Old April 21st 15, 03:01 AM posted to sci.astro.research
David Staup[_2_]
external usenet poster
 
Posts: 347
Default Can dark matter be small objects?

On 4/19/2015 11:24 PM, Phillip Helbig (undress to reply) wrote:
In article , Ray
Tomes writes:

Gas and dust is able to be detected by its effect on light. Large
objects glow from their own light. If intermediate objects were at
low temperature would they generally be detectable? There are many
orders of magnitude between dust and the dimmest starts. How many
of these could definitely not contribute to dark matter and why?


"Dark matter" is a bit of a misnomer. What most people mean these days
is "some sort of non-baryonic matter, other than neutrinos, which we
have not yet detected". This is the "DM" in, e.g., "LambdaCDM". Other
things can be dark, such as cold gas, dust, and so on. However, we have
good upper (and lower) limits on baryons from big-bang nucleosynthesis,
so while there are some dark baryons, they cannot be an appreciable
fraction of the dark matter.

It's also a bit of a misnomer since "dark" here means that it does not
interact electromagnetically. Yes, that means it doesn't glow, but it
also means that it doesn't reflect or absorb light. In other words, it
is transparent. At most it is weakly interacting (i.e. via the weak
"nuclear" force), but this is not something which can be investigated
astrophysically, so only gravitational effects are left. (Since we
don't know what it is, we don't know if it is self-interacting and hence
don't know if it can form macroscopic objects.)



Why is it that gravitational interacting is always mentioned separately?

Why not say: At most it is weakly interacting (i.e. via the weak
"nuclear" and gravitational forces).

[[Mod. note -- The reason is that the weak (nuclear) interaction is a
"short-range" force -- its strength drops exponentially with distance,
so it's utterly negligible for astronomical distances. Gravitation,
in contrast, is a "long-range" force, with (approximately) a 1/r^2
falloff with distance, so it can still be substantial at astronomical
distances.
-- jt]]
  #4  
Old April 23rd 15, 04:36 AM posted to sci.astro.research
Richard D. Saam
external usenet poster
 
Posts: 240
Default Can dark matter be small objects?

On 4/19/15 11:24 PM, Phillip Helbig (undress to reply) wrote:
In article , Ray
Tomes writes:

Gas and dust is able to be detected by its effect on light. Large
objects glow from their own light. If intermediate objects were at
low temperature would they generally be detectable? There are many
orders of magnitude between dust and the dimmest starts. How many
of these could definitely not contribute to dark matter and why?


"Dark matter" is a bit of a misnomer. What most people mean these days
is "some sort of non-baryonic matter, other than neutrinos, which we
have not yet detected". This is the "DM" in, e.g., "LambdaCDM". Other
things can be dark, such as cold gas, dust, and so on. However, we have
good upper (and lower) limits on baryons from big-bang nucleosynthesis,
so while there are some dark baryons, they cannot be an appreciable
fraction of the dark matter.


There is a question as to whether the "good upper (and lower) limits
on baryons from big-bang nucleosynthesis" must be modified
by high Z 'gold' collision experiments conducted inside
the Relativistic Heavy Ion Collider (RHIC),
an atom smasher at Brookhaven National Laboratory in Upton, New York.
Hints of Mysterious Particle Detected in 'Big Bang Soup'
http://www.livescience.com/47506-hea...ons-found.html
http://www.bnl.gov/rhic/news2/news.asp?a=4473&t=today
https://www.quantamagazine.org/20150...lider-awakens/
As established in physical chemistry,
reaction rates change
in solvents 'Big Bang Soup Z1' vs gaseous 'particle Z=1 ' phase.


It's also a bit of a misnomer since "dark" here means that it does not
interact electromagnetically. Yes, that means it doesn't glow,


In order for it not to glow, it must be extremely cold
and if it were baryonic matter, how cold would that be?

but it
also means that it doesn't reflect or absorb light. In other words, it
is transparent.


If dark matter objects had size dimensions on the order of meters,
then the dark matter galactic density on the order of 10^-24 g/cc
composed of these objects
would have a mean free path or optical density
such that they would not be optically visible under current methods
or in other words
these dark matter objects would in aggregate
be observationally transparent
in accordance with Beer Lambert Law
http://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law

At most it is weakly interacting (i.e. via the weak
"nuclear" force), but this is not something which can be investigated
astrophysically, so only gravitational effects are left. (Since we
don't know what it is, we don't know if it is self-interacting and hence
don't know if it can form macroscopic objects.)

The WIMP approach seems to be a dead end
based on negative experimental results
from the many current underground scintillation experiments.

Richard D Saam
  #5  
Old April 23rd 15, 04:37 AM posted to sci.astro.research
root[_2_]
external usenet poster
 
Posts: 8
Default Can dark matter be small objects?

Phillip Helbig (undress to reply) wrote:
In article , Ray
Tomes writes:

Gas and dust is able to be detected by its effect on light. Large
objects glow from their own light. If intermediate objects were at
low temperature would they generally be detectable? There are many
orders of magnitude between dust and the dimmest starts. How many
of these could definitely not contribute to dark matter and why?


"Dark matter" is a bit of a misnomer. What most people mean these days
is "some sort of non-baryonic matter, other than neutrinos, which we
have not yet detected". This is the "DM" in, e.g., "LambdaCDM". Other
things can be dark, such as cold gas, dust, and so on. However, we have
good upper (and lower) limits on baryons from big-bang nucleosynthesis,
so while there are some dark baryons, they cannot be an appreciable
fraction of the dark matter.

It's also a bit of a misnomer since "dark" here means that it does not
interact electromagnetically. Yes, that means it doesn't glow, but it
also means that it doesn't reflect or absorb light. In other words, it
is transparent. At most it is weakly interacting (i.e. via the weak
"nuclear" force), but this is not something which can be investigated
astrophysically, so only gravitational effects are left. (Since we
don't know what it is, we don't know if it is self-interacting and hence
don't know if it can form macroscopic objects.)


What intrigues me about DM is that beyond some point from the galactic
center the sum of luminous and dark matter, as a function of r, is
constant. Just how far out does that hold? Could this constancy be
a result of galactic formation or could it be true everywhere?

Could DM be proto baryonic matter?
  #6  
Old April 24th 15, 01:44 AM posted to sci.astro.research
root[_2_]
external usenet poster
 
Posts: 8
Default Can dark matter be small objects?

root wrote:
Phillip Helbig (undress to reply) wrote:
In article , Ray
Tomes writes:

Gas and dust is able to be detected by its effect on light. Large
objects glow from their own light. If intermediate objects were at
low temperature would they generally be detectable? There are many
orders of magnitude between dust and the dimmest starts. How many
of these could definitely not contribute to dark matter and why?


"Dark matter" is a bit of a misnomer. What most people mean these days
is "some sort of non-baryonic matter, other than neutrinos, which we
have not yet detected". This is the "DM" in, e.g., "LambdaCDM". Other
things can be dark, such as cold gas, dust, and so on. However, we have
good upper (and lower) limits on baryons from big-bang nucleosynthesis,
so while there are some dark baryons, they cannot be an appreciable
fraction of the dark matter.

It's also a bit of a misnomer since "dark" here means that it does not
interact electromagnetically. Yes, that means it doesn't glow, but it
also means that it doesn't reflect or absorb light. In other words, it
is transparent. At most it is weakly interacting (i.e. via the weak
"nuclear" force), but this is not something which can be investigated
astrophysically, so only gravitational effects are left. (Since we
don't know what it is, we don't know if it is self-interacting and hence
don't know if it can form macroscopic objects.)


What intrigues me about DM is that beyond some point from the galactic
center the sum of luminous and dark matter, as a function of r, is
constant. Just how far out does that hold? Could this constancy be
a result of galactic formation or could it be true everywhere?



I was hoping the moderator would have dropped my post above. Rather
than saying the sum of luminous and dark matter is constant, I should
have said that it is only a function of r.


Could DM be proto baryonic matter?

  #7  
Old April 24th 15, 01:46 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default Can dark matter be small objects?

In article , "Richard D.
Saam" writes:

There is a question as to whether the "good upper (and lower) limits
on baryons from big-bang nucleosynthesis" must be modified
by high Z 'gold' collision experiments conducted inside
the Relativistic Heavy Ion Collider (RHIC),
an atom smasher at Brookhaven National Laboratory in Upton, New York.


Is there any evidence that this is relevant to BBN?

In order for it not to glow, it must be extremely cold
and if it were baryonic matter, how cold would that be?


Anything above absolute zero emits radiation. You can calculate the
intensity as a function of wavelength from the temperature (under
certain assumptions).

If dark matter objects had size dimensions on the order of meters,
then the dark matter galactic density on the order of 10^-24 g/cc
composed of these objects
would have a mean free path or optical density
such that they would not be optically visible under current methods


Right: back issue of the ApJ, or bricks. :-) Right, we don't know
whether it consists of microscopic objects, but if so, presumably it
would have to be self-interacting with a cross section much larger than
for the weak interaction.

The WIMP approach seems to be a dead end
based on negative experimental results
from the many current underground scintillation experiments.


Absence of evidence is not evidence of absence. Many particles were
predicted and discovered only years or decades later. In the case of
dark matter, it is not even clear what properties it must have, or at
least the range is much larger, so it is not easy to say where to look.
  #8  
Old April 26th 15, 02:50 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default Can dark matter be small objects?

In article , "Phillip Helbig (undress to
reply)" writes:

Right: back issue of the ApJ, or bricks. :-) Right, we don't know
whether it consists of microscopic objects, but if so, presumably it
would have to be self-interacting with a cross section much larger than
for the weak interaction.


Microscopic --- macroscopic. If it consists of macroscopic objects,
they have to be held together, which implies some sort of
self-interaction. (The self-interaction could be gravity, but if
gravity is the only force involved, it is more difficult to form
objects, since accretion is efficient only after a certain mass has been
reached, and in order to reach this, one needs some other mechanism to
make bits of the object stick together and/or some mechanism for
cooling. Black holes are possible, but have been ruled out
observationally in many mass ranges.)
  #9  
Old April 26th 15, 03:05 AM posted to sci.astro.research
Richard D. Saam
external usenet poster
 
Posts: 240
Default Can dark matter be small objects?

[[Mod. note -- Note that arXiv:1503.07675 does NOT claim to have detected
a nonzero self-interaction cross section of dark matter. Rather, it claims
to have place an *upper limit* on any such cross section.
-- jt]]

On 4/23/15 7:46 PM, Phillip Helbig (undress to reply) wrote:
In article , "Richard D.
Saam" writes:

There is a question as to whether the "good upper (and lower) limits
on baryons from big-bang nucleosynthesis" must be modified
by high Z 'gold' collision experiments conducted inside
the Relativistic Heavy Ion Collider (RHIC),
an atom smasher at Brookhaven National Laboratory in Upton, New York.


Is there any evidence that this is relevant to BBN?

Current BBN simulation reactions
predict universe H, He, Li? gaseous abundances
but this does not negate the possibility of another BBN reaction phase
(liquid, solid and/or other)
as experimentally observed by RHIC
resulting in DM baryonic hydrogen phase
not observed in Baryonic Acoustic Oscillations
and cold so as not to glow
and such object size as to be transparent in aggregate.

In order for it not to glow, it must be extremely cold
and if it were baryonic matter, how cold would that be?


Anything above absolute zero emits radiation. You can calculate the
intensity as a function of wavelength from the temperature (under
certain assumptions).

DM object thermal emissivity
may be an indicator of these low temperatures although
related extremely long wavelengths are not measurable at this time
as calculated by
established black body spectrum peak wave length theory.

wave length (cm) = h*c/(4.96536456*Boltzmann*T)

Emission T K Emission wave length (cm)
2.2E+01 1.3E-02
2.7E+00 1.1E-01
1.0E+00 2.9E-01
1.0E-01 2.9E+00
1.0E-02 2.9E+01
1.0E-03 2.9E+02
1.0E-04 2.9E+03
1.0E-05 2.9E+04
1.0E-06 2.9E+05
1.0E-07 2.9E+06
1.0E-08 2.9E+07
1.0E-09 2.9E+08
1.0E-10 2.9E+09
1.0E-11 2.9E+10
1.0E-12 2.9E+11
1.0E-13 2.9E+12
1.0E-14 2.9E+13
1.0E-15 2.9E+14
1.0E-16 2.9E+15
1.0E-17 2.9E+16
So the secondary phase DM could be there
and at a temperature CMBR 2.7K
and not in thermal equilibrium with measured universe gaseous H, He Li?
and currently not thermally measurable.

If dark matter objects had size dimensions on the order of meters,
then the dark matter galactic density on the order of 10^-24 g/cc
composed of these objects
would have a mean free path or optical density
such that they would not be optically visible under current methods


Right: back issue of the ApJ, or bricks. :-) Right, we don't know
whether it consists of microscopic objects, but if so, presumably it
would have to be self-interacting with a cross section much larger than
for the weak interaction.

and what is the accepted weak interaction cross-section?

This reference
http://arxiv.org/abs/1503.07675
indicates dark matter cross-section
and resultant drag characteristics
for 72 studied galactic collisions
0.47 cm^2/g
This cross-section can be interpreted
as objects of ~meter size and density ~1 g/cc

If the context of the red, blue and green dots in
http://arxiv.org/abs/1503.07675 Figure 1,
the represented entities could be interpreted
as being separated in accordance with cross-section
gas 5E7 cm^2/g (calculated atom area/mass)
dark matter 0.47 cm^2/g
stars 7E-12 cm^2/g (calculated sun area/mass)
with the hydrodynamic mechanism
(with a drag coefficient defined by medium viscosity
and associated Reynold's number)
drag_coefficient*cross-section*substrate_density*c^2
as per
http://arxiv.org/abs/1503.07675 equation S2.
The stars inertially blow on through a viscous medium
while the DM is held up a little more in the viscous medium
and gas much more in the viscous medium.

A Pioneer 10 and 11 cross_section value 0.24 cm^2/g
may be computed
from the NASA published Pioneer dimensions
(pi/4)*pioneer_diameter^2/pioneer_mass
= (pi/4)*274^2/241,000 = 0.24 cm^2/g
and Pioneer 10 and 11 deceleration can be considered
substantiation of
http://arxiv.org/abs/1503.07675
DM separation mechanism.

What is the viscous medium?

There has been theoretical work on vacuum viscosity
arXiv:0806.3165v3 [hep-th] 14 Nov 2008
Hydrodynamics of spacetime and vacuum viscosity
that may be applicable here.

Richard D Saam
  #10  
Old April 30th 15, 03:24 PM posted to sci.astro.research
Richard D. Saam
external usenet poster
 
Posts: 240
Default Can dark matter be small objects?

[[Mod. note -- I'm allowing this last posting, but in the absence of
*new* points I think it's time to close this thread. -- jt]]

On 4/25/15 9:05 PM, Richard D. Saam wrote:
[[Mod. note -- Note that arXiv:1503.07675
does NOT claim to have detected
a nonzero self-interaction cross section of dark matter.
Rather, it claims
to have place an *upper limit* on any such cross section.
-- jt]]

Yes, your observation as well as Steve Willner's previous is correct
and my deficiency.
Amplification is necessary.
This reference
http://arxiv.org/abs/1503.07675
indicates dark matter cross-section
and resultant drag characteristics
for 72 studied galactic collisions
0.47 cm^2/g
This places limits on the DM object size(D)
and DM object density(rho_DM_object) of dark matter objects
assuming spherical DM objects with
area(A) cross-section = (pi/4)*D^2
and
DM object volume(V) = (pi/6)*D^3
and
DM object density(rho) = M/V
then
0.47 cm^2/g = (A/M)*(V/V) = (V/M)*(A/V)
= (1/rho)*((pi/4)*D^2/((pi/6)*D^3))
= (1/rho)*(3/2)/D
therefore
D = ((3/2)/0.47)/rho cm
N = rho_DM/M
M = rho_DM_object*V
DM Mean Free Path = 1/(sqrt(2)*pi*N*D^2)
assume
DM aggregate density(rho_DM) = 1x10^-24 g/cm^3

then for the limiting DM cross_section .47 cm^2/g
DM object density(rho) DM object size(D) DM Mean Free Path
g/cm^3 cm kpc
0.0319 99.8 122
0.319 9.98 122
3.19 .998 122
(any DM cross-section larger than 0.47 cm^2/g
with DM Mean Free Path 122 kpc
'close to the size of these colliding galaxies'
would be seen optically)

A Pioneer 10 and 11 cross_section value 0.24 cm^2/g
may be computed
from the NASA published Pioneer dimensions
(pi/4)*pioneer_diameter^2/pioneer_mass
= (pi/4)*274^2/241,000 = 0.24 cm^2/g
then for the Pioneer cross_section .24 cm^2/g
DM object density(rho) DM object size(D) DM Mean Free Path
g/cm^3 cm kpc
0.313 20.0 238
0.625 9.98 238
0.0625 99.8 238
0.0228 Pioneer as sphere 274 Pioneer size 238
(any DM cross-section ~ Pioneer 0.24 cm^2/g
with DM Mean Free Path 238 kpc
would not be seen optically)

then for the cross_section .01 cm^2/g (0.47 cm^2/g)
DM object density(rho) DM object size(D) DM Mean Free Path
g/cm^3 cm kpc
1.5 99.8 5,720
0.15 998 5,720
0.015 9,980 5,720
(any DM cross-section ~ 0.01 cm^2/g
with DM Mean Free Path 5,720 kpc
would not be seen optically)

then for the cross_section .001 cm^2/g (0.47 cm^2/g)
DM object density(rho) DM object size(D) DM Mean Free Path
g/cm^3 cm kpc
1.5 998 57,300
0.15 9,980 57,300
0.015 99,800 57,300
(any DM cross-section ~ 0.001 cm^2/g
with DM Mean Free Path 57,300 kpc
would not be seen optically)

These calculations can be viewed
in the context of the red, blue and green dots in
http://arxiv.org/abs/1503.07675 Figure 1,
the represented entities could be interpreted
as being separated in accordance with cross-section
gas 5E7 cm^2/g (calculated atom area/mass)
dark matter 0.47 cm^2/g
stars 7E-12 cm^2/g (calculated sun area/mass)
with the hydrodynamic mechanism
(with a drag coefficient defined by medium viscosity
and associated Reynold's number)
drag_coefficient*cross-section*substrate_density*c^2
as per
http://arxiv.org/abs/1503.07675 equation S2.
The stars inertially blow on through a viscous medium
while the DM is held up a little more in the viscous medium
and gas much more in the viscous medium.
and Pioneer 10 and 11 deceleration can be considered
substantiation of
http://arxiv.org/abs/1503.07675
DM separation mechanism.

The Bullet Cluster provides further evidence of DM decceleration
analogous to Pioneer deceleration
http://arxiv.org/abs/astro-ph/0608408
http://en.wikipedia.org/wiki/Bullet_Cluster

Bullet Cluster E0657-56 length
7.714E+23 cm 250 kpc
Bullet Cluster E0657-56 time after collision
4.730E+15 sec 1.50E+08 years
Bullet Cluster E0657-56 acceleration
2*length/time^2 = 6.895E-08 cm/sec^2
This deceleration is of the same order
as the Pioneer deceleration.

What is the viscous medium?

There has been theoretical work on vacuum viscosity
arXiv:0806.3165v3 [hep-th] 14 Nov 2008
Hydrodynamics of spacetime and vacuum viscosity
that may be applicable here.

The DM has to be very cold
so as not to observed.
DM object thermal emissivity
may be an indicator of these low temperatures.
Associated extremely long wavelengths are not measurable at this time
as calculated by
established black body spectrum peak wave length theory.

wave length (cm) = h*c/(4.96536456*Boltzmann*T)

Emission T K Emission wave length (cm)
2.2E+01 1.3E-02
2.7E+00 1.1E-01
1.0E+00 2.9E-01
1.0E-01 2.9E+00
1.0E-02 2.9E+01
1.0E-03 2.9E+02
1.0E-04 2.9E+03
1.0E-05 2.9E+04
1.0E-06 2.9E+05
1.0E-07 2.9E+06
1.0E-08 2.9E+07
1.0E-09 2.9E+08
1.0E-10 2.9E+09
1.0E-11 2.9E+10
1.0E-12 2.9E+11
1.0E-13 2.9E+12
1.0E-14 2.9E+13
1.0E-15 2.9E+14
1.0E-16 2.9E+15
1.0E-17 2.9E+16
So the secondary (solid, liquid or other) phase DM could be there
and at a temperature CMBR 2.7K
and produced as a BBN (solid, liquid or other) phase
separate from gaseous H, He Li
and not in thermal equilibrium with BBN produced and measured universe
gaseous H, He Li?
and currently not thermally measurable
or as a baryonic acoustic oscillation at first light (380,000 yrs)

Hydrogen molecular bonding mechanisms
at these extremely cold temperatures
would provide a stable DM object.

Richard D Saam
 




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