Questions tagged [dark-matter]

Questions about astrophysical observations, experimental searches, and theoretical models related to dark matter and its quanta.

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3 answers
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Why are dark matter and dark energy favoured over changes to our physical models? [closed]

I am instinctively skeptical of the existence of "dark matter" and "dark energy". Together, they strike me as being analogous to luminiferous aether -- something that was invented ...
1 vote
1 answer
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What if gravitation was the only force? [closed]

This is a follow up of Interactions within constituents of dark matter . I wonder about dark matter, and, naturally, compare it with our observable world. If gravitation would be the only force acting ...
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3 answers
107 views

Is Dark Energy Taking Over?

First question, trying to keep it simple 😃 Because it's constant it grows in magnitude as the universe expands, whereas normal matter does not? Is this accurate as far as we know?
1 vote
3 answers
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Interactions within constituents of dark matter

Inspired by Are the visible matter and dark matter separately segregated? I wonder if the constituents (I don't say particles, as we don't know) have actions and forces among themselves, that we ...
-3 votes
1 answer
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If we are sure dark matter is not modified space producing gravity can we spot an object deacceleration while moving through a dark matter cloud?

Can a moving object deacceleration caused by interaction with enviroment be measured while the object passes through a region populated by dark matter?
4 votes
1 answer
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Is the amount of dark matter per galaxy the same as you look back through time (further away from earth)?

In the hope that it may inform us about the development/evolution (if any) of dark matter over time, are there any differences (eg. in structure or concentration) in the dark matter at large radial ...
3 votes
3 answers
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Is Dark Matter really invisible? [duplicate]

From what I understand dark matter is called dark since it cannot be seen in the universe. My question is does it have to be invisible, as in to not interact with light ? Could it be that dark matter ...
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0 answers
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What is dark matter? [duplicate]

My friend asked me about dark matter and started saying that it is likely to be another world made up of things we say dark matter and energy said that quantum fluctuations may be the cause of dark ...
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0 answers
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If the axion is real, how can we detect it?

I have heard that axions are almost invisible, hence their use in dark matter and string theory. So how can we detect them?
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1 answer
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"Penrose Functional Degrees of Freedom" ( PFDoF) as a source of dark mass

In his book "Fashion, Faith, and Fantasy in the New Physics of the Universe" Sir Roger Penrose mention ( referring to his older works and specially Penrose-Hawking Theorem) the possibility ...
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1 answer
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Could Dark matter manipulation meet the negative energy requirements for an Alcubierre drive?

The biggest issue with the Alcubierre drive is that in order for it to expand the space behind the spacecraft, it would require negative mass with repulsive gravity. No such negative mass is known to ...
1 vote
3 answers
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Why doesn't frozen-out dark matter annihilate later during structure formation?

The so-called freeze-out of dark matter is based on a homogeneous description. However, in the later stages of the universe, where structures form, it seems very likely that the reaction rate would ...
6 votes
2 answers
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Attraction between dark matter

Why does dark matter not attract other dark matter in space, and form a giant structure?
12 votes
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Could Dark Matter form black hole?

Some people speculate that the mysterious dark matter in the universe could be tiny black holes. But on the other side, could dark matter particles attract each other by gravity and finally form a ...
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1 answer
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How to understand the derivation of thermally averaged cross sections?

$$ \frac{d\langle\sigma_\text{ion}^{nl} v\rangle}{d\ln E_\text{er}}=\frac{\bar\sigma_e}{8\mu^2_{\chi e}}\int q|f_\text{ion}^{nl}(k',q)|^2|F_\text{DM}(q)|^2\eta(v_\text{min})\ dq $$ How do I understand ...
4 votes
1 answer
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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 ...
3 votes
4 answers
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General Relativity "doesn't quite work" without dark matter?

I am taking an astrophysics course, and my astro professor said that "we need to introduce dark matter because Einstein's general relativity doesn't quite work without it". I wanted to ...
2 votes
3 answers
1k views

Why isn't the "Dark Matter" in the Bullet Cluster supermassive black holes?

I've seen several videos that claim that the Bullet Cluster is evidence for Dark Matter. The general idea is that the gas is trapped on one side of the collision and the light-bending "Dark ...
3 votes
0 answers
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Is shape dynamics capable of explaining dark matter?

I recently got introduced to the incredibly fascinating subject of Shape Dynamics: for example see https://arxiv.org/abs/1409.0105 Shape Dynamics uses conformal three-dimensional geometry to build up ...
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1 answer
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Are the visible matter and dark matter separately segregated?

I am having difficulty in visualising dark matter. Dark matter does not interact electromagnetically. Dark matter is inferred gravitationally. However it is not clear whether dark matter is present ...
-1 votes
1 answer
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What happens when antimatter hits dark matter?

What happens when antimatter hits dark matter? If its better for the thought experiment, lets say they collide with equal velocity. One particle for both would be enough, but an answer regarding ...
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0 answers
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Can dark matter be isolated from baryonic matter?

The above is an image to test Verlinde's emergent gravity theory (2016, https://arxiv.org/abs/1611.02269). The research team observered galaxies and masses beyond, used gravitational lensing (y-axis) ...
-1 votes
1 answer
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Which of Newton's shell theorems applies to a galaxy?

From this question I gathered that Newton came up with two sets of shell theorems, one for hollow spheres and one for solid. It was also said we should use the version inside a solid sphere to model ...
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1 answer
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Galactic Rotation Curves

While researching rotation curves, I've noticed a variety of velocity behaviors in different galaxies. In some, the velocity decreases, in others, it remains relatively constant, and in some cases, it ...
1 vote
1 answer
161 views

Could dark energy be explained via the use of a "gravitational charge"?

Could gravity be explained as the existence of a "gravitational charge", acting similarly to an electromagnetic charge but where like charges attract and opposite charges repel? A graviton ...
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1 answer
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Theoretically, is it feasible for the dark matter density to be constant and homogeneous, as dark energy is, and the two to be related?

I know that currently dark matter and dark energy are separate things, not related and one not deriving from the other. But if both are included in a generalized gravitation theory, the picture can ...
1 vote
2 answers
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How can I estimate the dark matter density for some specific galaxies by using the rotation curves?

I have rotation curve data (radius vs rotational velocity) for some specific galaxies. How can I estimate the dark matter density for those specific galaxies by using the rotation curves? Or is there ...
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Scalar Axion Field Amplitude Calculation in localised laboratory / Earth

This question concerns the paper "Axion Dark Matter: What is it and Why Now?", in the Appendix A.3 regarding equations related to the Axion Field. It states that by the Friedmann Equation, $$...
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Invisible decaying dark photon

I am interested in invisibly decaying dark photon to the dark sector. Let's assume the particles in dark sector are dark photon ($\gamma_D$), dark matter (DM) , and long lived particle scalar ($\phi_D$...
4 votes
2 answers
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Neutrino Nuclei Coherent scattering and the Dark Matter lower wall

Suppose that current and new forthcoming dark matter direct detection experiments find no evidence of Dark matter events and exclude interactions of hypothetical DM particles (like LSP or similar) in ...
4 votes
4 answers
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Galaxy Rotation Speeds and General Relativity

Is it true that the predictions from the General Theory of Relativity don’t match the observations of galaxy rotation speeds, and that this then started the search for dark matter? Is it only the ...
2 votes
1 answer
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What are Semi-Visible Jets?

I'm working on a project that aims to discriminate semi-visible jets (SVJs) in a QCD background, through learning from simulated data in the context of the LHC. I know that these are related to hidden ...
4 votes
3 answers
258 views

Axions and magnetic field

From what I know about the hypothetical particles "axions": Axions are candidates to be cold dark matter particles Dark matter interacts only gravitationally Some experiments use strong ...
1 vote
1 answer
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Does NFW profile work for any galaxy?

We use Navarro–Frenk–White (NFW) to calculate Dark Matter (DM) density. Can we use it for DM halo in any galaxy or is it used only for Milky Way (MW)?
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When calculating the amount of missing mass in a galaxy due to dark matter, do cosmologists take into account local effects of gravity on time? [duplicate]

If I understand correctly, massive objects cause time dilation, and so time seems to pass more slowly for observers closer to a massive object than those who are farther away. Do cosmologists take the ...
1 vote
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The 'core-cusp' problem for dark matter halos in larger galaxies

TLDR: Do observations of larger galaxies favour 'cuspy' dark matter halo distributions, as predicted by N-body simulations? I've been trying to understand the 'core-cusp' problem for dark matter halos ...
2 votes
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Slope in interaction strength vs mass for QCD axion

The theory models of QCD axion, i.e. those who solve the strong CP problem, all have a prediction that follows a band with a slope in the space interaction strength vs. axion mass. (1) What does cause ...
1 vote
1 answer
119 views

Dark matter, MOND or flattened gravitational fields? [closed]

Could there not be a third variant to explain why e.g. long-distance multistar systems rotate faster than Newton's law of gravity suggests? In addition to the Dark matter hypothesis and MOND then, ...
1 vote
1 answer
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Flat galaxy formation in a spherical dark matter halo

The dark matter halo of our own galaxy is assumed to be spherically symmetric. This sounds reasonable, since dark matter interacts gravitationally. However, stars in our galaxy are on a flat disk. ...
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1 answer
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Can outer star be captured by a more distance galaxy due to dark matter?

Imagine of an outer star lies between 2 galaxy cores with identical matter & dark matter distribution. If the outer star lies closer to galaxy core 1 and farther to galaxy core 2, the dark matter ...
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0 answers
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What is the evidence against a variable gravitational constant? [duplicate]

I understand that our main supporting evidence for dark matter is the anomalous speed of objects orbiting around the edges of distant galaxies. Is there a reason why dark matter solves this problem ...
0 votes
1 answer
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What if dark matter/energy did not exist?

What if dark matter and dark energy did not exist and were only due to a misinterpretation of the red shift of light or a measurement bias? What would be the implications/consequences?
3 votes
1 answer
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What happens to objects along spiral galaxy arms over long periods of time?

Observations of spiral galaxies reveal that objects within the same arm of a spiral galaxy move at around the same speeds, regardless of their distance from the center of the galaxy. Conversely, the ...
2 votes
2 answers
139 views

Likelihood of MACHOs being the best candidate for dark matter

Massive compact halo objects ("MACHOs") include a wide variety of hardly detectable bodies such as brown / white / black dwarfs and black holes, to name a few. If we take into account the ...
8 votes
1 answer
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Can mass-dimension-one fermion really be a dark matter candidate?

I am glad to hear back from the inventor @Dharam Vir Ahluwalia of ELKO! And I really appreciate the chance to have a in-depth discussion with the true experts of the ELKO theory. There is a growing ...
92 votes
7 answers
13k views

If dark matter only interacts with gravity, why doesn't it all clump together in a single point?

I'm a complete layperson. As I understand, dark matter theoretically only interacts with the gravitational force, and doesn't interact with the other three fundamental forces: weak nuclear force, ...
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Why doesn't the lack of electromagnetic repulsion between dark matter particles result in the formation of black holes? [duplicate]

From what I've researched dark matter isn't subject to electromagnetic forces, which I'm assuming implies that there is a lack of electromagnetic repulsion between dark matter particles. If there's ...
1 vote
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Anyonic and plektonic dark matter?

The most studied types of dark matter particles include supersymmetric particles, spin particles that are either boson or fermions. I wonder if there are research about dark matter being not particles ...
4 votes
2 answers
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If dark matter was created in the early universe and its formation released energy, is there any evidence of that energy in the cmb?

When atomic nuclei fuse, energy is released. Is there anything about the CMB energy distribution that suggests that dark matter could have formed from other particles that released energy?
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1 answer
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Could the energy emitted by galaxies contribute to the dark matter phenomenon?

I'm pondering a concept regarding the energy-mass conversion in the context of cosmology, specifically related to the light emitted by galaxies over billions of years. Einstein's famous equation E=mc^...

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