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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 votes
0 answers
57 views

Could dark matter be radiation pressure? [closed]

I watched Stephen Wolfram on a podcast explaining this idea last night. He said that dark matter could be explained as "spacetime heat". My contention is that stars and black holes trap a ...
1 vote
2 answers
54 views

Dark matter detector experiments above ground?

Most of the dark matter detectors I hear about are built below ground to shield from cosmic rays. One problem I see with this is what if the ground is also shielding dark matter from interacting with ...
2 votes
0 answers
89 views

Gravitational halos made of neutrinos...?

I have been recently interested in how halos made of standard model particles could be formed and behave. After asking some questions in this site, I was told about how neutrinos could form such halos....
0 votes
0 answers
34 views

Galaxies rotations speeds questions

We accept epic gravitational lensing effects around invisible supermassive black holes, but do we consider possible gentle lensing effects in huge galactic structures observations ? Do we take time ...
5 votes
4 answers
259 views

On gravitational waves of dark matter collisions

It is known that dark matter interacts gravitationally (and weakly in other ways as predicted by the WIMP model), and dark matter is present in the same space-time fabric as that of matter. When two ...
2 votes
3 answers
2k views

Is there a Dark Matter Paradox?

According to this preprint, The Importance of Being Symmetric: Flat Rotation Curves from Exact Axisymmetric Static Vacuum Spacetimes, spiral galaxies possess flat rotation curves without assuming Dark ...
56 votes
4 answers
4k views

Are modified theories of gravity credible?

I'm a statistician with a little training in physics and would just like to know the general consensus on a few things. I'm reading a book by John Moffat which basically tries to state how GR makes ...
3 votes
2 answers
340 views

Why are forces superimposable in Classical Mechanics? Does this also apply in higher theories like General Relativity and Quantum Mechanics?

In classical mechanics, forces are treated as vectors and are added linearly. Is this principle to be treated as an axiom or is there some underlying principle from which this is derived? And given ...
2 votes
1 answer
70 views

If dark matter is axion particles, how did such light particles slow down?

One candidate for dark matter is axions and there is tentative experimental evidence for their existence. Axions are very light, most models weigh them in at tiny fractions of an eV. It seems like ...
3 votes
2 answers
153 views

Does neglecting dark matter solve the Hubble tension?

If the total mass of the universe is smaller than estimated by neglecting the gravitational pull of dark matter, the estimated expansion rate should be greater. Does this consideration in the CMB ...
2 votes
1 answer
397 views

Contribution of dark matter to running of physical constants

I read that "essentially everything in the Standard Model impacts the running of every physical constant in the Standard Model. So, if there is even a single particle missing from the Standard ...
0 votes
1 answer
55 views

What if dark matter and anti-matter collided? [closed]

Considering we know both dark matter and antimatter can interact via gravity, just like regular matter, then that means the two can gravitationally interact. However, since dark matter does not ...
2 votes
1 answer
253 views

What's the meaning of 'cold' in the CDM model?

On Wikipedia, it says In cosmology and physics, cold dark matter (CDM) is a hypothetical type of dark matter. According to the current standard model of cosmology, Lambda-CDM model, approximately 27% ...
1 vote
1 answer
104 views

Does dark matter have mass?

When trying to understand what dark matter is, it is helpful to know that some properties of it can already be derived from various observations, such as, it only interacting via gravity and no other ...
0 votes
2 answers
72 views

Test of the primordial black hole solution to dark matter

One of the ideas that might solve some of the dark matter problem are the existence of many small black holes. There is evidence, in principle, for the existence of these small black holes via the ...
18 votes
1 answer
862 views

Dark matter and $SO(10)$ grand unification

$SO(10)$ grand unified theories nicely accommodate a massive $\sim 10^{14-15}\; GeV$ sterile neutrino. Would this be a viable dark matter candidate? I haven't found any specific material regarding ...
0 votes
3 answers
252 views

Dark matter and simulations of Modified Newtonian Dynamics

It is well known that dark matter was introduced to explain the orbits of stars in a galaxy. My main question is this: Were these calculations done using Newton or Einstein? People I ask tell me that ...
1 vote
0 answers
36 views

Equivalence of axion to fermion couplings

In order to solve the Strong CP problem through the axion, we introduce the axion-gluon coupling $$ \dfrac{a(x)}{f_a} \text{Tr}\, G\tilde{G}.\tag{1} $$ In a similar fashion, we may introduce the axion-...
4 votes
1 answer
239 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
1 answer
94 views

Why do people say that the $\Lambda$-CDM model has six independent parameters?

The Wikipedia article on the $\Lambda$-CDM model says that the model has six "independent parameters". It also says that the model has several "fixed" parameters and several "...
0 votes
1 answer
388 views

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 ...
0 votes
3 answers
213 views

Is it possible that dark matter and dark energy come from the same dark particle?

I've skimmed articles/blogs and watched videos around this issue, and the universal consensus is that dark matter and dark energy are two different things >> DM is attractive while DE is ...
0 votes
0 answers
41 views

Group velocity, phase velocity and signal velocity for axion like particles

In dark matter models of axion-like particles (ALPs), sometimes we get the field $$\phi=2\phi_0\sin(m_\phi c^2 t/\hbar)\cos(k_\phi x)$$ This is like an stationary field with amplitude $\phi_0$ (in m/s ...
-4 votes
1 answer
82 views

Yang-Mills mass gap caused by gluonballs or because dark matter WIMPs?

Yang-Mills quantum field theory predicts the existence of the lightest massive Bosonic (i.e. integer spin) particle. This massive Boson will be much lighter than the $W$ and $Z$ Boson and therefore ...
4 votes
2 answers
425 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 ...
0 votes
0 answers
53 views

Dark matter Thermal average cross section expansion

In many papers and books, including paper written by P.Gondolo & G.Gelmini in 1991, COSMIC ABUNDANCES OF STABLE PARTICLES: IMPROVED ANALYSIS, it is well known that for non relativistic gas, you ...
1 vote
2 answers
206 views

Is there an spherical symmetric Einstein vacuum solution which has circular orbits with flat velocities? Or a proof that it cannot exist?

The Schwarzschild solution shows decreasing velocities with larger orbits - and needs help from dark matter or MOND to explain galaxies. Apparantly no Einstein vacuum solution with flat velocities is ...
15 votes
3 answers
2k views

What's the argument(s) against dark matter being "normal" baryonic dust?

So I just finished watching "dark matter is not a theory". An understanding I gleaned from it is that dark matter is observed from the discrepancy between the amount (or perhaps energy? in ...
0 votes
3 answers
163 views

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
125 views

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 ...
0 votes
3 answers
108 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
100 views

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
50 views

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
110 views

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
1k views

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 ...
0 votes
0 answers
57 views

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 ...
1 vote
1 answer
77 views

"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 ...
0 votes
1 answer
215 views

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
145 views

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
2k views

Attraction between dark matter

Why does dark matter not attract other dark matter in space, and form a giant structure?
12 votes
2 answers
2k views

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 ...
3 votes
4 answers
2k views

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
117 views

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 ...
0 votes
1 answer
60 views

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
1k views

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 ...
0 votes
0 answers
35 views

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
152 views

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 ...
0 votes
1 answer
48 views

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
167 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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