# dark-matter's questions - English 1answer

547 dark-matter questions.

### 3 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 ...

### What kind of modified gravity could still explain all dark matter claims if we never more directly detect dark matter?

1 answers, 48 views dark-matter modified-gravity
I'm curious about this. I saw this: https://www.forbes.com/sites/brucedorminey/2018/07/18/is-time-running-out-on-dark-matter/ and they're suggesting that as direct searches for dark matter more and ...

### -1 Dark matter or Misunderstanding: Is it possible that the dark matter is simply missed variables in the math?

Is it possible that the dark matter is simply missed variables in the math? I am not a physicist but examples might include: effects of planetary and galaxy rotation, electromagnetic fields, ...

### 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-...

### Dark Matter Monojet signal

Dark matter can be observed at the LHC via a mono-jet signal i.e $pp\rightarrow XX + jet$. These signals can proceed via parton level processes like the mono gluon or mono photon ones. I was ...

### -1 Chaplygin gas as dark energy or dark energy plus dark matter, what is the issue?

0 answers, 22 views dark-matter dark-energy
One of the models of dark energy uses the Chaplygin gas (in the generalized version it can even provide a unified model of dark energy and dark matter). What is/are the issue/s with respect to the ...

### Could the rotation of far away galaxies appear faster than they really are? [duplicate]

The necessity of dark matter is suspect to me because of two distinct questions: We know that gravitational wells like that of massive stars do in fact slow the light coming from them to some degree. ...

### 3 “Mass Discrepancy-Acceleration Relation” in ΛCDM Paradigm

Rotation curves of galaxies seem to require more mass than observed - the conventional solution is the introduction of Dark Matter. Reading some articles on this topic (in particular a recent ...

### 1 Why doesn't Dark Matter participate in BBN reactions?

1 answers, 115 views big-bang dark-matter nucleosynthesis
This is a slightly different variation on an earlier question: In the very early universe, the hot plasma consisted of fixed amount of radiation (photons and neutrinos) and matter (electrons, protons,...

### 20 How long has dark matter been around?

2 answers, 3.368 views cosmology dark-matter
I've read that dark matter's existence is theorized because galaxies spin/clump in a way that would require much more mass than there appears to be. Also that there is gravitational lensing in places ...

### 45 Why do physicists assume that dark matter is weakly interacting?

2 answers, 5.263 views experimental-physics dark-matter
IceCube, XENON, etc, keep yielding negative results. If dark matter exists, it doesn't interact with baryonic matter at the energy ranges they can detect. The response is to build even bigger ...

### Has dark matter been ruled out? (March 2018 news)

2 answers, 322 views gravity dark-matter
I watched a YouTube post on a channel that normally has solid information about astronomy (as far as I can tell). But this episode states that (emphasis mine): …talking about the controversial ...

### 12 Integrated Boltzmann equation for dark matter

In Dodelson's book, the equation for a scattering process $a + b \Leftrightarrow c + d$ is given as \begin{align} a^{-3} \frac{\mathrm d (n_a a^3)}{\mathrm d t}&=-n^{\text{eq}}_a n^{\text{eq}}...

### 1 Could mass also experience a form of gravitational redshift?

Main question Gravitational redshift for photons are a wellknown phenomena where the electromagnetic radiation is reduced in frequency and thus the wavelenght is increased. The wave–particle ...

### 3 Why is the dark matter freeze-out temperature $T\sim \frac{m}{20}$ so generic?

For a dark matter of mass $m$, the typical freeze-out temperature is $T$ is usually assumed to be between $\frac{m}{20}-\frac{m}{25}$. But the freeze-out temperature depends upon the annihilation ...

We search for dark matter using direct techniques searching for a recoil of e.g. nobel gases atoms (Xenon1T,...) or indirect techniques (gamma-ray observations of dwarf spheroidal galaxies, the ...

### 43 Why isn't dark matter just ordinary matter?

8 answers, 4.330 views cosmology astrophysics dark-matter 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 ...

### 16 How did we 'discover' dark matter? [closed]

I'm an astrophysics student and I've been researching this topic and there is one point that keeps eluding me. How did the scientific community realize that there had to be dark matter in the ...

### Why can't the Higgs vacuum energy clump to galaxies and act as dark matter (instead of dark energy)? [closed]

The Higgs field has a nonzero vacuum expectation value which contributes to the energy density of the Universe. Energies contribute to the curvature of spacetime and affected by gravitational ...

### 1 Is it sufficient to consider the uncharged dark matter and a $\mathbb{Z}_2$ symmetry to prevent its decay into photons?

Higgs boson, though electrically neutral, can decay to produce a pair of photons i.e., have electromagnetic interactions. See the answer here. Therefore, it appears that making dark matter ...

### 1 What might be the equillibrium Distribution Function of Dark Matter?

Can we assign a thermal distribution function to Dark Matter(not necessarily known ones)? Is it possible that they won't even follow thermal distribution function and maybe a function of something ...

### 1 Experimental constraints on dark matter pressure?

The $\Lambda$CDM model assumes collisionless dark matter, so that its pressure $P=0$. But what are the best experimental constraints on $P$? I guess on $P/\rho$ in fact…

### 2 Could a black hole's dark matter content be determined?

2 answers, 54 views black-holes astrophysics dark-matter
I recently attended a talk where the speaker said that it is impossible for us gain information about the history of particles which make up the black hole. i.e we won't know if the black hole was ...

### 3 Why are cosmological contents often modeled as fluids?

Why is it that in cosmology, everything is treated as a "fluid"? What justifies modelling radiation, matter, etc. as "fluids" (even dark energy??)? When does it break down -- surely at small scales ...

### 5 Is cold dark matter made of Higgs bosons?

2 answers, 818 views dark-matter higgs wimps
This paper (2010) hypothesizes that Higgs bosons might be absolutely stable, allowing them to serve as a cold dark matter candidate: The Higgs boson is in the backbone of the standard model of ...

### 3 How do we know that the dark matter is cold or non-relativistic?

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 ...

### 1 Dark Matter and Gravity

If gravitational lensing implies that Dark Matter exerts gravity onto light then why are the stars and regular matter not clustering around Dark Matter?

### 2 Seminal Paper On 3.5keV Sterile Neutrino?

There have been a number of papers on the astronomically observed 3.5keV line, the most recent being "Searching for the 3.5 keV Line in the Deep Fields with Chandra: The 10 Ms Observations". These ...

### 1 What was the DAMA dark matter detector reporting in 2013 and why does no-one else believe them?

I understand DAMA is a dark matter detector but I don't understand how it works, and what it's seeing. They claim to have a seasonal variation in their signal which is supportive of a certain type of ...

### 2 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. ...

### 3 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 ...

### 17 What gives mass to dark matter particles?

Assuming that dark matter is not made of WIMPs (weakly interacting massive particles), but interacts only gravitationally, what would be the possible mechanism giving mass to dark matter particles? If ...

### 5 Is there any evidence for dark matter besides gravitational effects?

2 answers, 158 views gravity dark-matter modified-gravity
Is there any evidence for dark matter besides just its gravitational effects? What I’m getting at is...why are we so quick to assume it’s any kind of “matter” at all rather than just some unexplained ...

### 16 Is dark matter repulsive to dark matter? Why?

I think I saw in a video that if dark matter wasn't repulsive to dark matter, it would have formed dense massive objects or even black holes which we should have detected. So, could dark matter be ...

### 1 Article presenting first evidence for dark matter?

What are the papers where the first evidence for dark matter related with the stability of galactic discs, and the orbits of galaxy satellites?

### -4 Is dark matter unmanifested matter? [closed]

I am by no means a physicist. I lack credentials and formal education. I did however have an interest in theoretical physics when I was younger. This post is to present my thoughts/idea/theory or ...

### Can Dark Matter be light and cold at the same time?

1 answers, 52 views cosmology mass dark-matter
In most of the papers that I encounter, the mass range for Dark matter is generally taken to be 1-1000 GeV. Is it possible that dark matter is of the order of few MeV? What observation is violated in ...

### 2 How do we know that galaxies are not in the process of flying apart?

A major reason for believing in the existence of dark matter is that the stars in the outer regions of galaxies are moving too fast to remain bound to their galaxies, given only the estimated mass of ...

### -2 Can black holes effect light or just what the light reflects off of [closed]

1 answers, 51 views particle-physics dark-matter
Can light be shifted or stopped by anything other than a solid? I ask because when observing black holes you can see light funneling into the sphere. My thought was that if what’s being pulled into ...

### Could dark matter/dark energy turn out to be tachyonic?

Today, I was watching the Inexplicable Universe with Neil deGrasse Tyson. He spoke about Dark Matter, Dark Energy, and then he spoke about Tachyons. Naively, I thought what if the reason we can't ...

### 29 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 ...

### 3 Where/how to learn about dark matter?

I am a physics student and as far as I know dark matter is beyond the topics included in my grade career. Are there any serious book on the subject? Any serious set of lectures somewhere in Internet?

### -1 What models do physicists use in predicting the movement of stars in a galaxy that has lead to a wide-spread conviction that Dark Matter exists?

My (possibly poor) understanding of the argument for Dark Matter's existence is that stars in a large galaxy move more slowly than "they should" (presumably due to either some simplified model of the ...

### Estimating total mass inside the Sun's orbit

I'm trying to estimate the local density of dark matter at a given radius, $r=R_0=8\text{kpc}$. I also have values for the core radius, $a=5\text{kpc}$, and circular velocity of the Sun, \$v_{\text{...

### 1 Dark Matter as possible an explanation for Coronal Heating

2 answers, 113 views thermodynamics sun dark-matter
It's my understanding that the mechanism behind Coronal Heating - why the Corona is so much hotter (> 1,000,000 K) than the surface of the Sun (6,000 K), and the mechanism by which the energy gets ...

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

2 answers, 1.087 views general-relativity black-holes dark-matter
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 ...