Questions tagged [dark-matter]
Matter not observed directly but inferred to exist based upon its gravitational effects.
629
questions
1
vote
0answers
58 views
Gravitational non-linearities and Dark Matter/Energy
I had read Significance of Gravitational Nonlinearities on the Dynamics of Disk Galaxies (https://arxiv.org/abs/1909.00095), was wondering
Is there good reason to think that gravitational non-...
1
vote
1answer
24 views
How the dark matter density parameter appears in Big Bang Nucleosynthesis (BBN)?
I know that it is possible to obtain the light element abundances ($^{4}\mathrm{He}, \mathrm D, ^{7}\mathrm{Li}$ etc.) and to determine the baryon-to-photon ratio $\eta$ from the total baryon ...
-3
votes
0answers
40 views
Could the increasing expansion of the universe be proof of the multiverse? [closed]
Einstein included a cosmological constant in his equations, this leads to the search for dark matter as I understand. Currently we fail to detect this dark matter.
So what if it isn't there, but ...
-1
votes
0answers
31 views
What might be the effect on galaxy rotation of a linearly and uniformly increasing galaxy mass (over time)? [closed]
In Cosmic clocks: a tight radius–velocity relationship for H i-selected galaxies, Meurer, Obreschkow, Wong, Zheng, Audcent-Ross and Hanish identify that galaxies behave as clocks, rotating once a Gyr ...
10
votes
2answers
877 views
Absorption of dark matter by black holes
Our Universe consists of about 22% Dark Matter (DM). Such matter is the main stuff of galaxies. Also, Black Holes (BH) live in galaxies. We know that DM is subject to gravitational interaction. So, ...
11
votes
3answers
1k views
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 ...
1
vote
0answers
89 views
Could dark matter actually be matter which resides in a different spatial dimension? [closed]
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
votes
0answers
22 views
Where can I find the star 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
vote
1answer
66 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
votes
1answer
59 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
votes
1answer
44 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
votes
1answer
36 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
votes
2answers
201 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
vote
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
votes
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 ...
1
vote
1answer
121 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).
...
1
vote
2answers
73 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?
0
votes
0answers
20 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
121 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
votes
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
votes
0answers
43 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 ...
0
votes
0answers
27 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?
0
votes
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
votes
1answer
170 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
vote
0answers
27 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
votes
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
votes
0answers
94 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
votes
2answers
1k views
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 ...
-3
votes
2answers
77 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
votes
1answer
108 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 ...
0
votes
0answers
15 views
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
votes
2answers
130 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
votes
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?
1
vote
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
votes
1answer
120 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
votes
2answers
72 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
votes
1answer
72 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 ...
1
vote
0answers
16 views
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 $< ...
-2
votes
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
vote
1answer
124 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
votes
1answer
69 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
votes
1answer
51 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
votes
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
votes
1answer
113 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
votes
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
votes
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
votes
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
vote
1answer
66 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 ...
-2
votes
1answer
93 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
votes
1answer
66 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 ...
