Questions tagged [dark-matter]
Matter not observed directly but inferred to exist based upon its gravitational effects.
626
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Is dark matter inside galaxies different from dark matter in intergalactic space?
I just read a text about astronomy and when talking about dark matter the author says:
[...], the dark matter responsible for the orbits of the stars in the Milky Way is probably different from the ...
0
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0answers
55 views
Latest news about Cold Dark Matter [on hold]
Can someone give me the most recent "generally accepted" vision on Cold Dark Matter cosmology ?
A general overview of Cold Dark Matter cosmology can be found on Wikipedia
https://en.wikipedia.org/...
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Average distance between galaxies in bullet cluster?
I was doing some research on dark matter and for that I need the average distance between the galaxies of the bullet cluster.
I can find that data on the internet so can someone please give me the ...
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0answers
84 views
Could dark matter actually be matter which resides in a different spatial dimension? [on hold]
I have at best a rudimentary understanding of the math in this side of physics, so bear with me. I am also aware of this question, but it was asked and answered 4 years ago and I don't want to ...
0
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0answers
15 views
Where can I find the start distribution data of our galaxy?
I am doing some research on dark matter and for that I need data of star distribution in our Galaxy.
Is there any mathematical law that predicts the distribution pattern of stars in our Galaxy?
1
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1answer
65 views
Dark matter in the time window between freeze-out and kinetic decoupling
Background
After the freeze-out, when all annihilations have stopped, the abundance ($Y=\frac{n}{s}$) of thermal dark matter species no longer changes with time. However, it is still kept in kinetic ...
0
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1answer
55 views
Can dark matter explain the unusual orbit of transnettunian objects? [closed]
While we are struggling to find an hypothetical planet 9 to explain the unusual orbit of transnettunian objects, I was wondering if it could be just dark matter.
We know that the universe is mostly ...
0
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1answer
40 views
What crystals are being used in this project to detect dark matter?
I recently read an article about "groundbreaking Australian research in the hunt for dark matter", in which it said:
We use highly purified crystals to detect dark matter. These crystals react when ...
0
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1answer
34 views
Sterile neutrinos findings
There is a relatively new paper https://arxiv.org/abs/1805.12028 of MiniBooNE on measurements of neutrino oscillations that can only be explained by the postulate of a sterile neutrino. I also read ...
8
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2answers
195 views
Why does nobody ever consider the possibility that the universe is not smooth?
Disclaimer: I'm not an astronomer, physicist, mathematician, etc. so this is a question from a complete newbie.
One of the greatest mysteries of our age is "where is the dark matter?" The universe ...
1
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1answer
20 views
Elastic scattering between particles and forces
If a WIMP interacts elastically with a nucleus, for which force they interact? Weak force? The same for neutrons, it interacts via strong force? The only elastic scattering i know is the Rutherford ...
0
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0answers
8 views
How to calculate spin-dependent and spin independent scattering cross sections for different elements inside stars?
To calculate capture-rate of dark matter particles by stars, we need to calculate spin-dependent and spin-independent scattering cross sections for different elements inside stars.
How it is ...
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1answer
116 views
Can dark matter actually be gravitational radiation?
It seems to exist like only space distortion, and it seems to move just like radiation (specially when galaxy clusters collide, dark matter goes trough unaffected just like some type of radiation).
...
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2answers
71 views
Gravity as a repulsive force
As we know that universe is expanding, why can't we think the gravitational force as repulsive in nature in the realms of dark matter and dark energy?
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0answers
19 views
Primordial dark matter synthesis
In standard cosmology, there is a general picture of:
Primordial nucleosynthesis, i.e., when and how, nuclei or elements were formed. It is not quite tested, but it is more or less known where it ...
2
votes
2answers
116 views
How do you distinguish between missing momentum from a neutrino and from dark matter?
I thought googling this would give me an answer quite quickly, but actually couldn't find much, so maybe it's a silly question. But I read that dark matter searches rely on measuring missing momentum ...
0
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0answers
45 views
What is the mass/cross section of Dark Matter candidates?
I understand that experiments at LUX, XENON and LHC have eliminated many of the predicted masses for candidates for Dark Matter. Does anyone know what the current lowest possible mass is that hasn't ...
0
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0answers
42 views
What proof do we have that dark matter is matter? [duplicate]
The Dark matter page on CERN's official website describes dark matter as if it were regular matter just with some mysterious properties. This was a surprise to me because every time someone mentions ...
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0answers
26 views
Generally how much faster are stars on the outskirts of galaxies orbiting than they should be?
This assumes there is no mysterious matter causing the extra speed. Are they orbiting say 10% faster than expected etc?
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2answers
58 views
Dark Matter Stars Triggering Nebula Collapse
I'm interested in theories of dark matter where dark matter is an equivalent copy (or copies) of ordinary matter. Each equivalent sector is hidden from the others would see the others as 'dark' and ...
2
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1answer
167 views
Formula for the bias of galaxies
From the article "Large-Scale Galaxy Bias", I try to deduce the equation that my teacher told me which links 2 quantities:
the global number density of galaxies
the local number density of galaxies
...
1
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0answers
26 views
Demonstration about large-scale bias of galaxies
From this article : https://arxiv.org/pdf/1611.09787.pdf , I try to deduce the equation that my teacher told me which links 3 quantities :
1) the global number density of galaxies
2) the local ...
0
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0answers
11 views
How does the cosmological constant dominate cold matter perturbations?
I have been studying inhomogeneous universe in physical cosmology, whereupon I arrive at cold matter perturbations which are dominated by various background fluids. I understood the solutions for the ...
2
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0answers
93 views
Spiral galaxy stability
Is there a limit of baryonic masses $M_{B}$ ($M_{B}=M_{\star}+M_{g}$), beyond which a spiral galaxy is no longer rotationally supported? Like for example: Could spiral galaxies of baryonic masses $M_{...
9
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2answers
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Why is the distribution of dark matter in a Galaxy different from the distribution of normal matter?
The dynamics of a galaxy are driven by gravity. And dark matter experiences the same gravitational forces as normal matter. The effects of other forces are very small in comparison. So why is the ...
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2answers
76 views
Dark matter composition [closed]
I assume that dark matter is made of heavy neutrinos.But wouldnt they be converted into neutrinos with less mass throygh weak interaction?So dark matter isnt made of neutrinos.I think there is truly ...
0
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1answer
105 views
Dark Matter Wave Particle Duality
CERN is looking for dark photons, and they are seeking to look for interactions with the Higgs boson with the dark photon.See link here. So in other words a dark photon - a mediator for dark matter is ...
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0answers
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How well supported by observations is the hypothesis that concentrations of dark matter are essential to galaxy formation?
Much work regarding the formation and early evolution of galaxies seems to assume that galaxies form based on clumps dark matter.
The following observations indicate that some galaxies started with ...
2
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2answers
128 views
Why physical / cosmological models that have been falsified weren't abandoned? [closed]
Before anything, I'd like to say that I'm a layman (non physicist) and english is not my main language; I apologize if my choice of words make me sound rude / arrogant, that is not my intent.
I often ...
0
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1answer
53 views
Dark matter and supersymmetric particles
Is there a possibility to consider supersymmetric particles of fermions and bosons as the unknown dark matter?
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0answers
48 views
Dark Matter search, why DAMA collaboration does not publish $S_0$?
Results from recent experiments are starting to come in, mostly in the direction of not confirming the annual modulation measuremements published by the DAMA/Libra collaboration. In the search for ...
2
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1answer
101 views
How do they know the numbers of the energy pie chart of the universe?
They say that the total energy of the universe consists of 4.9\% ordinary matter, 26.8\% dark matter and 68.3\% dark energy. I hear this pie part in virtually every lecture in cosmology. How do we ...
5
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2answers
71 views
How do we know that dark matter energy density scales as $\rho\propto a^{-3}$?
How do we know that dark matter energy density scales as $\rho\propto a^{-3}$?
3
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1answer
70 views
Why use xenon in the search for dark matter?
The XENON dark matter research project is an interesting long-running project that strives to detect dark matter. I understand that the basic principle of the project design is that WIMPs are expected ...
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0answers
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Axion CDM analogous to reheating?
In a paper on Axions Peccei writes:
When the Universe goes through the PQ phase transition at $T ∼ f_a >
> Λ_{QCD}$ the QCD anomaly is ineffective. As a result, early in the
Universe $< ...
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1answer
58 views
Explanation for Dark Matter [closed]
My question relates to dark matter (DM). I understand that primordial black holes have been ruled out statistically as a candidate for DM. Could “dead” primordial black holes leave behind curved ...
1
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1answer
123 views
Is a galaxy made up of dark matter really a galaxy?
So I am watching a video discuss Dragonfly 44. The galaxy is made up almost entirely of dark matter and is 100x dimmer than the Milky Way galaxy.
Wouldn't this mean it is just a large clump of ...
0
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1answer
67 views
Could six copies of the universe exist only interacting by gravity? [closed]
The ratio of dark matter to matter is roughly in proportions $1:5.4$
This suggests that if there were about 6 Universes placed in the same space that were completely invisible to each other, except ...
0
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1answer
50 views
Are pressureless, collisionless and self-interacting dark matter all synonymous?
Is there any distinction between pressureless, collisionless and self-interacting dark matter or does being one imply the other?
3
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2answers
3k views
Do we need dark matter and dark energy, if the behaviour of the universe in its initial stages was similar to that of the Sun? [closed]
According to CMBR the universe was a cloud of plasma and was a perfect black body, $380,\!000$ years after big bang.
But the Sun in our solar system also is in the state of plasma, thus making it a ...
0
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1answer
111 views
Neutron decay discrepancy
I have been reading the article Neutron Lifetime Puzzle Deepens, but No Dark Matter Seen on the present methods of measuring the life span of neutrons The bottle method measures a mean lifespan which ...
0
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2answers
43 views
Does Higgs Boson influences with Gravity?
Does Higgs Boson influences with Gravity? Is there any way that if the universe is expanding Higgs particle has influence over it?
3
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1answer
119 views
Why does not dark matter gather and form celestial bodies? [duplicate]
since the only thing we know about dark matter that it "attracts" and affect our Baryonic matter's momentum and speed, which means that it does have mass of a sort.
so why didn't we witness a ...
3
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1answer
101 views
black dwarf stars and dark matter
Today we understand that a black dwarf star represents a hypothetical star that is the result of the complete consumption of the energy of a white dwarf which is the remnant of a star of little or ...
1
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1answer
65 views
Which decoupled first? The dark matter or the CMB photons?
According theories that work best for the structure formation which happened first in the history of the evolution of the Universe, the decoupling of dark matter or the decoupling of photons? How sure ...
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1answer
92 views
Does string/M-theory provide a solution to the dark matter/energy problem?
Would string theory or any other propesed UFT help explain, at least in theory what the other 95 percent of matter and energy in the universe are about?
It seems as thaugh there is a reacurring theme ...
2
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1answer
65 views
Why doesn't the centrifugal force cause rotating dark halos to flatten?
Consider a spherical cloud of dark matter like the spherical halo around our galaxy. Please see the diagram below
Assuming that the halo is purely made up of dark matter which has only gravitational ...
2
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1answer
86 views
Dark matter should be nonrelativistic at $1$ KeV or earlier. Why?
If the dark matter (DM) is non-relativistic at freeze-out and if the kinetic decoupling occurs much later than freeze-out, it is called cold dark matter. More precisely, it is stated that if the DM ...
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3answers
88 views
Can we measure dark matter's effect on spacetime?
I'm not a physicist or mathematician at all, just very curious, so sorry if this is a dumb question.
Now I understand we can make astronomical observations and say, "Oh, 85% of gravity in the ...
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1answer
35 views
Does dark matter need a second force to collect in ordinary matter?
Some experiments search for dark matter interactions at the center of bodies like the Sun and Earth, assuming that if there is some interaction with ordinary matter that allows dark matter to lose ...
