Questions tagged [dark-matter]

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

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Are weakly interacting massive particles interacting weakly?

When talking about Weakly Interacting Massive Particles (WIMPs) as Dark Matter candidates, do we mean that they interact via the weak force (possibly communicating with the SM by exchange of $W^\pm$ ...
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Dynamical effects of the scale invariance of the empty space: The fall of dark matter? [closed]

André Maeder, Honorary Professor in the Department of Astronomy of the Faculty of Science at the University of Geneva (UNIGE) believes that the commonly accepted model of the Big Bang followed by an ...
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CMB anisotropies without dark matter

One of the strongest hints of dark matter are the CMB anisotropies and the peaks. What should a non-dark matter theory do in order to reproduce that evidence? I mean, what is the feature that a pure ...
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Why does the speed of sun play a role in dark matter detection

I'm reading the book supersymmetry and beyond from Gordon Kane and got a bit confused at the point where he started explaining how we can check whether the signal we got at a detector is truly because ...
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The exploding star iPTF14hls and weakly interacting dark matter, and birth sites of stars

Could iPTF14hls contain a huge amount of weakly interacting dark matter? Because the dark matter is weakly interacting, it wouldn't get expelled by explosions, and its strong gravity could suck more ...
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Why does dark matter form halos?

Earlier questions (e.g. How does Dark Matter form a halo?) referred to the distribution of dark matter in the galaxy. My question is different (not a duplicate). I wonder why dark matter would form a ...
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Why is dark matter called dark matter?

It has been observered that spiral arm formation galaxies exist. This is a problem because due to the laws of gravitation, stars close the galactic center should orbit with a much higher angular ...
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Could Dark Matter be found by building a Hadron Collider that is the size of the earth?

I believe that through the current Collider created by CERN is finding out new data on a small scale. What if Dark matter could be found by an even bigger Collider like one that could be built around ...
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Dark black hole information

Consider a large cloud of dark matter moving under its own gravity. I understand that dark matter doesn't normally lose its kinetic energy, because dark matter doesn't radiate heat away. However, if a ...
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Dark matter mass and weak interactions

If dark matter forms halos around galaxies, it must have invariant mass. In the Standard Model, elementary particles acquire mass usually through the weak interactions with the Higgs field. Does this ...
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Is matter - dark matter symmetry possible?

The gravitational lensing evidence suggests massive and relatively dense accumulations of dark matter in space. However, dark matter collapsing to dense regions is unlikely due to energy conservation. ...
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Gravitational collapse of dark matter [duplicate]

The gravitational lensing evidence suggests the existence of massive and relatively dense regions of dark matter. However, if dark matter interacts only gravitationally, what would stop it from ...
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Average Density of the Universe over Time

For reference: Referring to a question I posted in Feb. 2015: Could Hyper-Massive Black Holes be due to Dark Matter in the Early Universe? User10851 answered, and I replied. He then replied to my ...
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What forms first: the dark matter halo or the galaxy?

I read that in the early Universe dark matter forms halos, and dust and gas inside those halos formed the first ever galaxies. I am curious to know whether the dust and gas formed the galaxy inside a ...
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Is it possible that dark matter is just a bunch of gravitational waves interacting with one another? [duplicate]

Since stars and other objects are much closer to one another towards the centers of galaxies where dark matter tends to be found, it seems that it would follow that events forming gravitational waves (...
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Why does dark matter form a halo, Unlike normal matter? [duplicate]

Hi I am curious to know why dark matter forms a halo? Or why doesn't normal matter form a halo.What is the difference between the two My level is amateur
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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 ...
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Dark matter vs black holes

I want to think simple in the way black holes and dark matter interact with matter. Whats differences exists between dark matter particle and a quantum description of a black hole full of dark matter?...
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Neutrinos always travel at same speed? [duplicate]

Neutrinos have mass, and only interact with gravitional and weak force, what make it very difficult to detect. Neutrinos is known to travel very closer to speed of light and have very small mass ...
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Is it possible for the Oort cloud to account for the Dark Matter issue?

I'm no cosmotolicist, so forgive me if I'm completely off the mark here. A few years back, I read that there is not enough matter in the universe to account for the gravitational forces at play, ...
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How was dark matter formed?

I am a homeschooled student in year 7. I am interested in dark matter. Specifically its formation. I am curious about when and how dark matter was first formed. Also what part it played in the ...
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How do you model an NFW Dark Matter Halo?

I am trying to reproduce the results of Sofue's 2016 paper (https://arxiv.org/abs/1510.05752). I'm able to use least squares minimization to model the bulge and disk effectively, but I get into ...
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Overlap between experimental searches for axion and WIMP dark matter

Are there experiments which search for WIMPs that also set limits for the axion? I'm doing a literature review on axions, and I've been told I should include a brief overview of WIMP searches as they ...
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Why should dark matter be stable (i.e., non-decaying)?

People say that the dark matter has to be stable and electrically neutral. Since there is no particle in the Standard Model which is both stable (non-decaying) and electrically neutral it cannot ...
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Why is dark energy called dark?

I know that dark matter is called dark because it interacts very weakly/doesn't interact electromagnetically. Is the same for dark energy, or the name is due to something else? In particular, can dark ...
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Can Kepler's third law be used to find the mass of a black hole without incorporating dark matter?

Ignoring dark matter, Kepler's third law would yield different results for the mass of the black hole depending on the distance of the orbiting star from the black hole. Is it possible to make the ...
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CMB evidence for nonbaryonic dark matter

I'm trying to get my head around what the adiabaticity of fluctuations in the CMB actually tells us. So far as I understand, it points to dark matter because: For the sheer number of galaxies we ...
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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 ...
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How does dark matter distribution help to identify it's composition

A question regarding this recently released data, and the paper https://arxiv.org/abs/1708.01538 that details it's distribution: Abstract: We use 26 million galaxies from the Dark Energy Survey (...
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Where are particles dissappearing in thermal equilibrium?

I am incredibly puzzled over dark matter relic abundance plots like this (taken randomly from google), where it shows number density of some particle species in a comoving volume In thermal ...
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345 views

What is the vacuum alignment problem?

Can someone explain with a simple example what is meant by vacuum alignment in a field theory? Recently I have heard this term in a seminar and when I asked the speaker I got an unsatisfactory answer: ...
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SUSY particles as Dark Matter

In SUSY, why is only the neutralino considered the best candidate for dark matter, why not the other SUSY particles?
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Software to predict gamma ray spectrum from dark matter decay and anihilation

Im looking to study the gamma ray spectra of dark matter models. Is there a "standard" or widely used software that can produce these spectra given some user defined model?
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physical meaning of dark matter virial radius

As I have read in the literature, the virial radius of a dark matter halo is the radius of a sphere such that the density $\frac{M_{\text{virial}}}{\frac{4\pi}{3}R_{\text{virial}}^{3}}=97.2\rho_{\text{...
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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 ...
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Fall of the number density $n$ with the scale factor $a(t)$ for a relativistic particle species in equilibrium?

Consider the thermal dark matter (DM) scenario. Before the dark matter got frozen out, it was both in chemical and thermal equilibrium with the other particles in the early universe. At this point of ...
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Why people think dark matter as a massive particle? Couldn't it be gravitational waves?

Dark matter is said to be present in the galaxies which helped galaxies to exist in the first place forming the glue to attach all the matter in the galaxies. Given that dark matter never been seen ...
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Dark matter and LIGO

In addition to the functioning LIGO detectors (two in USA and one in Italy), I am aware there are some gravitation wave detectors under construction. More detectors should provide more statistical ...
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Where does the rate of mergers per halo in the “Did LIGO detect dark matter?” paper come from?

It was recently proposed that dark matter (DM) could be made of primordial black holes (PBHs) of $\sim 30 M_{\odot}$, like the first ones detected by LIGO. This idea was written in "Did LIGO detect ...
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Can the centers of galaxies act as particle accelerators?

At the centers of galaxies, the amount of dark matter is much higher than that of ordinary matter. So the centers can effectively gravitationally attract and accelerate ordinary matter- without much ...
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Why are dark matter and dark energy invisible?

I know that dark energy and dark matter do not emit or absorb light, but how exactly does that work on an atomic/subatomic level? What happens in an interaction between the dark matter/energy and ...
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When and where was WIMP dark matter formed?

Is the formation of WIMP dark matter confined to the high number densities associated with the early stages of the formation of the universe or are conditions in the collisions of black holes such ...
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Why does our Solar system not feel the effects of dark matter the way our galaxy does? [duplicate]

It is said that stars rotate around the nucleus of our galaxy at too high a speed than should be possible based on the amount of visible matter. An explanation given for this is dark matter. However, ...
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Can dark matter be ordinary matter in a quantum coherent state?

The hypothetical dark matter halo envelopping a galaxy looks like to a gaussian distribution of position probability density of a particle in a quantum coherent state. How long should a wave function ...
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Does the orbital velocity of stars in a galaxy equal the rotational velocity of the SMBH at the centre?

Pretty straightforward, couldn't find anything on Google, was hoping someone might know. Thanks in advance.
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Is dark matter due to observational error

It seems to me that the idea of dark matter grew from doppler measurements of the velocities of the outer stars of spiral galaxies. It was assumed that what was being measured was the orbital ...
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Why isn't Dark Matter distributed among ordinary matter?

DM: dark matter; OM: ordinary matter I know that DM has a distribution which is mostly concentrated in the center of galaxies. This was mainly deduced by accounting for gravitational effects on the ...
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What is the maximal particle mass one can create via the LHC? Can we create dark-matter particles via the LHC?

Thanks to the LHC one can make particles collide and annihilate into other particles. Therefore, currently, what is the mass of the most massive particle one could create theoretically given the ...
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Why can't planets scoop up dark matter?

The density of dark matter is way to low to affect solar system dynamics a measurable amount, see this question. High-speed particles will zip right through the planet (see this question), but what ...
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Relation between baryonic mass and luminosity [duplicate]

I have one simple question: How do we know that dark matter is not just ordinary matter which is simply not luminous? For example if we would take a black rock and put it somewhere in the universe, ...