Questions tagged [dark-matter]

Matter not observed directly but inferred to exist based upon its gravitational effects.

Filter by
Sorted by
Tagged with
0
votes
2answers
46 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 ...
0
votes
0answers
30 views

Formula for the 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 2 quantities : 1) the global number density of galaxies 2) the local ...
4
votes
1answer
142 views

How are the dark matter (DM) thermalization rates derived in singlet DM model?

This well-cited paper talks about a minimal renormalizable extension to the Standard Model (SM) to incorporate particle dark matter (DM) into it by adding a real scalar field $S$ which (unlike the ...
1
vote
1answer
160 views

Dark Matter and Equivalence Principle

Dark Matter effects show up in galaxies. Why isn't it considered as a violation of equivalence principle instead of assuming all these extra non-interacting particles as gravitational mass and ...
-4
votes
2answers
78 views

Dark matters, what it is made of? [closed]

Where does DARK MATTER come from? How it is made? Can someone make it artificially? Can it be altered also like normal matter? Or what is it different from matter and anti-matter, and what is it made ...
7
votes
1answer
237 views

Would dark matter (as a BEC) be captured by Black Holes, Neutron Stars, etc?

Suppose that dark matter is in the form of a Bose-Einstein Condensate, with a DeBroglie wavelength of ~10,000 LY. (There are some axion models of DM where the axions are in a BEC.) In this model, the ...
1
vote
0answers
23 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 ...
1
vote
0answers
91 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_{...
2
votes
1answer
133 views

Exclusion limits on particle dark matter

I'm trying to make sense on how the upper limits of the cross section of particle dark matter (WIMPs) are computed, like in the figure below. This is taken from an article on dark matter searches. ...
8
votes
2answers
922 views

Dark Matter vs Modified Gravity

Why do cosmologists and astrophysicists assume that the reason for the higher velocities of outer stars in galaxies is due to matter at all? The name dark matter seems misleading. Couldn't gravity ...
11
votes
1answer
692 views

Justification for new theories of Particle Physics and General Relativity

In reference to arxiv:1212.4893v3 and arxiv:1206.5078v2 papers of Ma and Wang, they have proposed new theories in particle physics, the weakton model where quarks and leptons are formed using these ...
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 ...
16
votes
1answer
1k views

When galaxies collide, what happens to dark vs. light matter?

I have read that galactic collisions have been used as evidence demonstrating the effects of dark matter. In particular, that luminous matter slows down and interacts while dark matter shoots through, ...
-3
votes
2answers
70 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 ...
8
votes
2answers
1k views

Could dark matter be curved pockets of spacetime left over from the big bang?

My understanding of general relativity is that gravitation is equivalent to spacetime curvature and is proportional relative to localized mass. Traditionally, we conceptualize that massive things ...
0
votes
1answer
102 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
14 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 ...
0
votes
1answer
49 views

Dark matter and supersymmetric particles

Is there a possibility to consider supersymmetric particles of fermions and bosons as the unknown dark matter?
2
votes
2answers
121 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 ...
1
vote
0answers
44 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
67 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 ...
46
votes
8answers
5k views

Why isn't dark matter just ordinary matter?

There's more gravitational force in our galaxy (and others) than can be explained by counting stars made of ordinary matter. So why not lots of dark planetary systems (i.e., without stars) made of ...
5
votes
2answers
65 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 $\rho\propto a^{-3}$?
1
vote
1answer
117 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 ...
1
vote
1answer
54 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
10 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 $< ...
-1
votes
1answer
57 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 ...
5
votes
3answers
172 views

Distribution of dark matter in galactic halos

Often dark matter around galaxies is referred to as a 'halo'. I've seen the galactic rotation curves, but I'm having trouble visualizing how the dark matter is distributed for a typical rotating ...
1
vote
1answer
64 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
47 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?
0
votes
1answer
642 views

What is the amount of dark energy in the Universe, in joules?

I'm toying with an idea, and need absolute amounts of dark energy. I'd also like the same for dark matter. If these values are not estimated, why not?
0
votes
1answer
95 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 ...
4
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
2answers
39 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?
-2
votes
1answer
86 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 ...
3
votes
1answer
118 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 ...
1
vote
1answer
58 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 ...
3
votes
1answer
90 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 ...
2
votes
1answer
78 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 ...
2
votes
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 ...
1
vote
3answers
84 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 ...
4
votes
2answers
312 views

How do we know that the dark matter is cold or non-relativistic? [duplicate]

According to the $\Lambda$CDM parametrization of the Standard Model of Big Bang cosmology, the universe contains a cosmological constant $\Lambda$ associated with $73\%$ dark energy, $23\%$cold dark ...
31
votes
1answer
5k views

Why is Anti-helium so important in the search for dark matter?

I've been reading/hearing that if the AMS satellite measures a significant flux of anti-helium in cosmic rays, that would be an irrefutable proof of dark matter. I was wondering: Why is that? what is ...
6
votes
2answers
1k views

Could dark matter be made of black holes? [duplicate]

I have read these questions and their answers: Dark matter black holes Could Dark Matter form black hole? Does dark matter originate from matter falling into a black hole? following up dark matter ...
0
votes
1answer
171 views

Dark matter pressure

Dark matter is suppose to form large halos of unknown yet type of particle with a specific density density profile. Does the dark matter halo can be viewed as a fluid of particles with density and non-...
1
vote
1answer
34 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 ...
1
vote
0answers
40 views

A doubt in Modified gravity

I am new to dark matter and modified gravity so excuse and inform me if I am wrong. If changes are made in the Friedman equations then there wouldn't always be an underlying action action principle. ...
-3
votes
1answer
49 views

Could dark matter be normal matter that is beyond the observational horizon?

As I understand it, matter that is too distant for its light to reach us would not be observable, and the CMB is the limit of what is observable from our location within the universe. Could what is ...
1
vote
1answer
57 views

Might a “normal matter” body orbit a dark matter body?

Are there any main stream theories of dark matter that would allow for it to form bodies which could participate in orbits with normal matter? So, say, could a normal matter planet be captured and ...