Questions tagged [dark-matter]

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

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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, ...
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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, ...
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How are the constants for the NFW profile determined?

I'm trying to understand the NFW profile and how it causes a flat rotation curve. $$ \rho(r) = \frac{\rho_0}{\frac{r}{r_s}\left(1+\frac{r}{r_s}\right)^2} $$ I think I've got why it causes a flat ...
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Do galaxies have a halo of neutrinos and cosmic microwave background?

If virial arguments as in "How can dark matter collapse without collisions or radiation?" allow concluding that dark matter could collapse to galactic halos purely gravitationally, then is this true ...
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Gravity of dark matter [closed]

Why call it dark matter not invisible matter? (or 'The Force') (or 'ether' like we used to) Since time is bunk (thanks Douglas Adams) and space is bunk (thanks Einstein et al) why is anyone really ...
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Current constraints on Dark Matter self-interaction from galactic profiles

The self-interaction of dark matter may be small but it cannot be negligible if it is able to dissipate energy to relax into galactic clumps (necessary to explain galaxy rotation curves). According ...
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Dark matter and relativistic mass change [duplicate]

Could the requirement of a dark matter for the missing mass in the universe simply be explained by objects having high relativistic mass change with respect to other objects? If this is not the case, ...
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Why sun has a velocity with respect to the dark matter halo?

I was reading that Sun has a velocity with respect to the local dark matter halo of about 244 km/s. Both sun and the dark matter halo revolve around the Milky way. Since the local dark matter halo ...
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Could quasars produce elements heavier than oxygen?

I have read that supernovae are the main producers of elements heavier than oxygen. I just wonder whether quasars, which have been around a long time just like supernovae have, could have had a ...
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Emergent Gravity theory by Verlinde

Erik Verlinde has proposed a emergent structure of Gravity in a recent paper Emergent Gravity and the Dark Universe Abstract from paper cited above Recent theoretical progress indicates that ...
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Relationship between orbital radius, mass, and orbital velocity

I have a question regarding the relationship between a body's orbital radius, mass, and orbital velocity. I understand that there is the equation $V = \sqrt{\frac{GM}{R}}$, where $V$ is the orbital ...
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How does dark matter decrease predict CMB anystropies?

Measured matter overdensities today are $\delta_{0m}=\frac{\Delta \rho_m}{\rho_m}\geq 1$, which means that at the time of photon decoupling, they must have been $\delta_{dec,m}\geq 10^{-3}$. But this ...
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What can we infer about heavy dark matter?

Until recently, most of the ideas regarding the nature of dark matter revolved around WIMPs. Now that the LHC has not turned up any evidence of SUSY, people are starting to earnestly look towards ...
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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 ...
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How did dark matter become a relic?

Why did the decay rate of the dark matter particles fall when the temperature of the Universe $T_U$ dropped below dark matter mass $M_{DM}$? In particular, why can it not decay into lighter particles ...
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Spin-dependent and spin-independent interactions of the dark matter

What is meant by spin-dependent and spin-independent interactions of the dark matter with the nuclei? How is the interaction between nucleus and DM modeled? What can we conclude if the DM-nuclei ...
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How can Bose-Einstein Condensate improve our understanding of Dark Matter and Dark Energy?

There was this news a few days ago about NASA attempting to create the Coldest Spot in the Universe1 aboard ISS, to study further the properties of Bose-Einstein Condensate. I can understand that at ...
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How to calculate annihilation cross section, given effective operator for Datk Matter?

Suppose I have an effective operator of the form $\frac{1}{\Lambda^{2}}$$\bar{\chi}\chi\bar{q}q$, where $\chi$ is an fermionic DM and 'q' is the quark. Given this operator, How do I calculate the DM ...
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What is the percentage of dark matter in the galaxy? [closed]

Assuming the mass of the stars and gas within NGC 5055 is $8\times10^{10} M_{sun}$. What is the percentage of the dark matter in it?
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Is spacetime supersymmetry realized at TeV scale? and more questions on supersymmetry [closed]

Is spacetime supersymmetry realized at TeV scale? If so, what is the mechanism of supersymmetry breaking? Does supersymmetry stabilize the electroweak scale, preventing high quantum corrections? ...
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Direct Dark Matter Detection: relative velocity between WIMPs & Nuclei

In direct dark matter detection it is said that the relative velocity between the WIMPs, which form a DM halo, and the target nuclei on earth is of order $100 \frac{\text{km}}{\text{s}}$. How does one ...
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Different cold dark matter density parameters from early- and late-Universe observations

Edit: @John Rennie, thank you for your good and concise review of how the parameters of the $\Lambda$CDM model evolve with time. However, the answer I was looking for was a different one (sorry for ...
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Do compact stars heat the CDM halo?

I understand that a single WIMP interacts weakly with individual baryons, or probably even planets, but black holes should be able to slingshot the individual WIMPs they encounter. According to the ...
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How can there be regions in space with only dark matter in it, if dark matter derives from entropic gravity?

In Verlinde's theory on entropic gravity, the gravity between matter is modified over large distances. Mass(es) move towards other mass(es) because of the entropy increase (in the form of space atoms ...
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Do field theories exist for dark energy/matter? [closed]

Has a mathematical theory ever been composed to describe either dark energy or dark matter (or both)? In other words, the standard model describes fermions and bosons; does a model exist to describe ...
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Light thru dark matter and space etc

I saw another question on here concerning light speeds and specifically concerning different types of light waves etc. The typical answer dealt with the speed of light in a vacuum but how do we know ...
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Cannot neutrally charged objects describe the effects of dark matter?

For the galaxy cluster that dark matter describes: I think the picture would be something like a shell. The outer layer would be the galaxies and the inner layer would be n-bodies of neutrally charged ...
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How does Dark Matter form a halo?

Here are the velocity components of the Milky Way (according to Sofue et al. 2013) out to 20 kpc. The vertical axis is $k$ $s^{-1}$. The horizontal axis is $kpc$. The purple line is the rotation ...
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How bad would it break physics if dark matter was not “particles”?

Some people suggest that dark matter might not even be particles at all —that’s just what physisists expect to find with reference to what they are familiar with. But, I learned, from layman books of ...
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Why acceleration at the edge of the galaxy is lesser?

I was going through Modified Inertia using the Hubble Scale Casimir effect the theory is proposed by M.E. McCulloch. The theory says it can explain different anomalies such as EmDrive, Galactic edges,...
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Could Dark Matter be used as reaction mass for a propulsion device?

Assuming a best case scenario, where humans are able to discover a way to interact with Dark Matter, could we use dark matter like a row boat uses the water? Assuming Dark Matter is made of WIMPs, ...
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Dark matter annihilation cross section

What is the meaning of upper limit of annihilation cross section? Sometimes I have seen that $\langle\sigma v\rangle = 3.0 \times 10^{-26}\,{\rm cm}^{3}\,{\rm s}^{-1}$ or $2.0 \times 10^{-25}\,{\rm cm}...
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Possible explanation of dark matter/dark energy? [duplicate]

Could dark matter or dark energy be explained by a massive amount of 'mass' creating far reaching gravity far beyond our galaxy? Pulling things away from us at an accelerated rate? Or maybe a '...