Questions tagged [dark-matter]

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

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238 views

Would dark matter (as a BEC) be captured by Black Holes, Neutron Stars, etc?

Suppose that dark matter is in the form of a Bose-Einstein Condensate, with a DeBroglie wavelength of ~10,000 LY. (There are some axion models of DM where the axions are in a BEC.) In this model, the ...
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1answer
142 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 ...
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164 views

Remaining Potential Experimental Particle Physics Discoveries at the TeV Scale?

With the discovery of the Higgs Boson, some have been calling it the end of experimental particle physics for our generation, due to the fact that all of the particles predicted by the standard model ...
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115 views

Milky Way: where does it end?

The milky way galaxy, as is typical for spirals (and others?), has a relatively flat rotation curve except very near the center: Eventually, at great enough distances, almost the entire mass of the ...
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68 views

Active-sterile mixing for KeVins

People sometimes talk about KeV mass sterile neutrinos as a warm dark matter candidate. I think they call them KeVins (horrible name btw). Now, In order for it to be a good dark matter candidate it ...
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299 views

Partial waves and the velocity expansion of a scattering cross section

I'm confused about the relation between the velocity expansion of a scattering cross section and the angular momentum (partial wave) expansion. For example, for dark matter annihilation, we write $\...
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1answer
136 views

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 ...
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203 views

Cosmological constant problem and dark matter theory by Henke

Christian Henke has recently proposed one approach for the solution of the cosmological constant problem and of the dark matter dynamics: Quantum vacuum energy in general relativity Abstract: The ...
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124 views

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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63 views

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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262 views

Why would be axions be a candidate for warm/cold dark matter?

Axions are the current main favoured candidate for the identity of dark matter. While their masses are sub-$\mathrm{eV}$, why is it that they would be cold or possibly warm dark matter candidates ...
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134 views

Dark matter “hair” flowing through the earth

Gary Prézeau of NASA's JPL has done some calculations of how dark matter might be focussed by the Earth's gravitational field (publication preprint), and the results show some remarkable hairy ...
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63 views

How sensitively can we detect a moon-sized mass of dark matter?

Suppose there is an object with the mass of the moon made entirely of dark matter. Suppose that somehow, it has the same mass density as the moon. By dark matter I mean matter that does not interact ...
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140 views

Bulge-Disk decomposition in galaxies

I'm starting a new project on dark matter astrophysics in which I have to extract from some data (I will write some below) the surface brightness, to later construct the mass density profiles of de ...
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86 views

How does dark matter interact with light?

Most articles I read say that dark matter are weakly interacting particles. Are there any theories on how dark matter may interact with light/electromagnetic radiation?
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290 views

Particle dark matter coherent scattering?

Particle dark matter coherent scattering direct searches rely on the scattering of the DM particle off a nucleus (Xe, Si, Ge, NaI etc). The wisdom is this is coherent scattering: so the rate ~atomic ...
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24 views

Demonstration about large-scale bias of galaxies

From this article : https://arxiv.org/pdf/1611.09787.pdf , I try to deduce the equation that my teacher told me which links 3 quantities : 1) the global number density of galaxies 2) the local ...
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91 views

Spiral galaxy stability

Is there a limit of baryonic masses $M_{B}$ ($M_{B}=M_{\star}+M_{g}$), beyond which a spiral galaxy is no longer rotationally supported? Like for example: Could spiral galaxies of baryonic masses $M_{...
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44 views

Dark Matter search, why DAMA collaboration does not publish $S_0$?

Results from recent experiments are starting to come in, mostly in the direction of not confirming the annual modulation measuremements published by the DAMA/Libra collaboration. In the search for ...
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10 views

Axion CDM analogous to reheating?

In a paper on Axions Peccei writes: When the Universe goes through the PQ phase transition at $T ∼ f_a > > Λ_{QCD}$ the QCD anomaly is ineffective. As a result, early in the Universe $< ...
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40 views

A doubt in Modified gravity

I am new to dark matter and modified gravity so excuse and inform me if I am wrong. If changes are made in the Friedman equations then there wouldn't always be an underlying action action principle. ...
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1answer
100 views

Effects of dark matter

I was wondering, when sims of galaxies show that we need dark matter to account for the movement of outer stars, are models taking into account relativistic effects on gravity? The tips of spiral ...
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1answer
68 views

Do attraction between two galaxies count for dark matter?

We know that the uniform rotation curve of individual spiral galaxies does require presence of some form of dark entity (matter). Does the attraction between two (or more) spiral galaxies also require ...
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1answer
71 views

Like the Higgs sector of the standard model, is there a SUSY sector which is also such a sector?

This question arose from an application of the virial theorem that showed how Bose-Einstein condensates of astrophysical dimension could arise from condensing clouds of normal phase bosons. If these ...
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19 views

Population histograms and relationship between size of galactic disk and amount of dark matter

I am interested in seeing a plot of dark to baryonic matter ratios in terms of the galactic disk size (when it applies, as not all galaxies fit into disk shapes, and probably analyzing disk galaxies ...
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2answers
93 views

Does dark-matter attract itself with gravity as light-matter does, and if so where are the dark stars and galaxies?

Does dark-matter interact with gravity like light-matter does, or does dark matter interact only with light-matter via gravity?
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26 views

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 ...
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41 views

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…
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104 views

What if Dark Matter is Majorana Fermion?

Few reasons to believe Dark Matter is Majorana fermion: https://arxiv.org/abs/1711.03877: second contra argument by Jordan and Pauli. "A non vanishing zero-point energy of elementary fields should ...
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238 views

Can matter/antimatter “annihilation” produce “dark matter”?

I was thinking about the following reasoning: If a matter and antimatter reaction produces energy, this energy would have particles itself. I found out (reading...) that one (the main?) product are ...
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18 views

Can strongly radiating matter cause dark matter to clump?

Ordinary matter clumps under gravitational attraction only when it loses energy through radiation. Dark matter supposedly doesn't clump since it can only exchange energy with itself and ordinary ...
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30 views

Does the virial theorem prohibit dark matter BH's on any size or timescale, or just make them very unlikely?

I've read other Q's on dark matter/black holes, but none seem to be technically specific enough to clarify this point. I understand so far, that because classic CDM doesn't interact in ways that ...
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38 views

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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53 views

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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201 views

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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225 views

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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1answer
50 views

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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53 views

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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103 views

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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90 views

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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80 views

How did we find the composition of the universe when our observation of it is limited

The standard model of cosmology indicates that the total mass–energy of the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. For the standard cosmological model, the ...
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54 views

How do we measure the masses of far away galaxies?

One piece of evidence that is supposed to show that dark matter exists is the rotation curve diagram. Apparently Fritz Zwicky used the Viral Theorem to make a prediction which does not fit with the ...
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29 views

Could classical equipartition theory if not a Maxwell Boltzmann blackbody distribution apply to translucent dark matter?

Given Dark Matter is most likely warm but non-radiating are there any classical field channels for it to communicate its inertial mass?
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107 views

How do trace element abundances show that dark matter exists in both baryonic and non - baryonic forms?

I can't seem to find an answer to this question anywhere, any help would be greatly appreciated. Thanks in advance.
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77 views

Are Axinos an attractive candidate for Dark Matter and why?

Out of the SUSY DM candidates Gravitinos and Neutralinos are considered more likely than Axinos however I cannot find much on these. NB: Note the difference between axions and axinos.
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Form factor and EFT form factors for an interaction of a WIMP and a nucleon

On the third paragraph(right column) of page 1 of the paper, http://journals.aps.org/prc/abstract/10.1103/PhysRevC.89.065501, it says, "Because the momentum transfer in the scattering is large ...
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104 views

Galactic Rotation Curve Calculation

Can anyone give the list of formulas used for plotting the Galactic Rotation Curves? I mean, is there only the formula for linear velocity or is the formula for the gravitational potential also ...
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1answer
160 views

Dark Matter and Equivalence Principle

Dark Matter effects show up in galaxies. Why isn't it considered as a violation of equivalence principle instead of assuming all these extra non-interacting particles as gravitational mass and ...
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35 views

Do clouds of dark matter cool and contract?

If dark matter participates in the weak interaction, clouds could cool via thermal neutrino radiation...? And even if does not participate in the weak interaction, clouds should contract via ...
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74 views

Does this phrase in “Knocking On Heaven's Door”, refer to gravitons?

This is an extract from Knocking On Heaven's Door, by Randall (2011) The suprising fact is that if you have a stable particle whose mass corresponds to the weak energy scale that the LHC will ...