Questions tagged [dark-matter]
Questions about astrophysical observations, experimental searches, and theoretical models related to dark matter and its quanta.
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When calculating the amount of missing mass in a galaxy due to dark matter, do cosmologists take into account local effects of gravity on time? [duplicate]
If I understand correctly, massive objects cause time dilation, and so time seems to pass more slowly for observers closer to a massive object than those who are farther away. Do cosmologists take the ...
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Does NFW profile work for any galaxy?
We use Navarro–Frenk–White (NFW) to calculate Dark Matter (DM) density. Can we use it for DM halo in any galaxy or is it used only for Milky Way (MW)?
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The 'core-cusp' problem for dark matter halos in larger galaxies
TLDR: Do observations of larger galaxies favour 'cuspy' dark matter halo distributions, as predicted by N-body simulations?
I've been trying to understand the 'core-cusp' problem for dark matter halos ...
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Slope in interaction strength vs mass for QCD axion
The theory models of QCD axion, i.e. those who solve the strong CP problem, all have a prediction that follows a band with a slope in the space interaction strength vs. axion mass.
(1) What does cause ...
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Dark matter, MOND or flattened gravitational fields? [closed]
Could there not be a third variant to explain why e.g. long-distance multistar systems rotate faster than Newton's law of gravity suggests?
In addition to the Dark matter hypothesis and MOND then, ...
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Flat galaxy formation in a spherical dark matter halo
The dark matter halo of our own galaxy is assumed to be spherically symmetric. This sounds reasonable, since dark matter interacts gravitationally. However, stars in our galaxy are on a flat disk. ...
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Can outer star be captured by a more distance galaxy due to dark matter?
Imagine of an outer star lies between 2 galaxy cores with identical matter & dark matter distribution. If the outer star lies closer to galaxy core 1 and farther to galaxy core 2, the dark matter ...
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What is the evidence against a variable gravitational constant? [duplicate]
I understand that our main supporting evidence for dark matter is the anomalous speed of objects orbiting around the edges of distant galaxies. Is there a reason why dark matter solves this problem ...
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What if dark matter/energy did not exist?
What if dark matter and dark energy did not exist and were only due to a misinterpretation of the red shift of light or a measurement bias?
What would be the implications/consequences?
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What happens to objects along spiral galaxy arms over long periods of time?
Observations of spiral galaxies reveal that objects within the same arm of a spiral galaxy move at around the same speeds, regardless of their distance from the center of the galaxy. Conversely, the ...
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Why doesn't the lack of electromagnetic repulsion between dark matter particles result in the formation of black holes? [duplicate]
From what I've researched dark matter isn't subject to electromagnetic forces, which I'm assuming implies that there is a lack of electromagnetic repulsion between dark matter particles.
If there's ...
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How much gravitational lensing do we see from the Milky Way?
I assume that the Milky Way has a dark matter halo just like any other. If that is the case, if we look at a huge part of our own galaxy, do we actually see the gravitational lensing effect? How ...
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Event after big bang that cause dark matter [closed]
When the universe was formed by the Big Bang, what was the event that made some matter visible to us, while some became dark matter?
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Likelihood of MACHOs being the best candidate for dark matter
Massive compact halo objects ("MACHOs") include a wide variety of hardly detectable bodies such as brown / white / black dwarfs and black holes, to name a few. If we take into account the ...
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Is the $σ8$ tension in the ΛCDM cosmology evidence that the amount of Dark Matter (DM) in the universe is increasing?
Strong evidence is provided by recent cosmological studies that “clumpiness” in the large scale structure (LSS), as measured by $σ8$, is decreasing (for example, “Hyper Suprime-Cam Year 3 Results…”, X....
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Why can't Dark matter be made up mostly of Neutrinos? [duplicate]
It's said that Neutirnos can only make up a tiny fraciton of dark matter.
So why can't Dark matter be mostly made up of Neutrinos?
Why can't there just be a huge number of them?
I suspect myself that ...
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Lifetime of a WIMP [duplicate]
I have been watching videos of WIMP's and have a simple question..
The larger the particles, the shorter their lifetime. A top quark is so massive that it cannot form a "stable" bond with ...
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Modified Gravity against Dark Matter
I am looking for examples of Modified Gravity theories that have been developed with the aim of dispensing dark matter, besides Milgrom's MOND, Bekenstein's TeVeS, and the recent relativistic version ...
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Could the energy emitted by galaxies contribute to the dark matter phenomenon?
I'm pondering a concept regarding the energy-mass conversion in the context of cosmology, specifically related to the light emitted by galaxies over billions of years.
Einstein's famous equation E=mc^...
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Axion production from vacuum realignment and the strong CP problem
I am trying to understand axions as a possible candidate for dark matter. My understanding of one of the mechanisms by which energy could up in the axion field is by an initial misalignment between ...
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Could Dark Matter have negative pressure?
Is it possible for dark matter to have negative (but negligible) pressure? How small should it be to fit with observations? Dark matter pressure is actually known and measured?
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What are Semi-Visible Jets?
I'm working on a project that aims to discriminate semi-visible jets (SVJs) in a QCD background, through learning from simulated data in the context of the LHC. I know that these are related to hidden ...
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Can dark matter be explained by defects of spacetime?
Dark matter is believed to be a substance of unknown origin with mass that is distributed in space.
Can the same observed effects be explained by an intrinsic curvature of regions of space without ...
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Anyonic and plektonic dark matter?
The most studied types of dark matter particles include supersymmetric particles, spin particles that are either boson or fermions. I wonder if there are research about dark matter being not particles ...
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Why doesn't a dark matter halo just collapse to a disc?
According to this and this answer, and as far as I understand these answers, dark matter halos cannot collapse to a black hole because, due to uncoupling from the EM field, they are unable to radiate ...
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Star equations of hydrostatic equilibrium for a mix of 2 fleebly interacting gases/fluids and interaction term
For a single matter species, the equations of hydrostatic equilibirum for a star are
\begin{eqnarray}
\nabla^2 \phi &=& 4\pi G \rho\\
\vec{\nabla} P + \rho \vec{\nabla}\phi &=&0
\end{...
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Is there dark matter in intergalactic space?
Reference: the rotation speed of galaxies in a galaxy cluster:
Is the dark matter associated with each galaxy in a cluster, sufficient to explain the rotation speed of galaxies in the cluster, or ...
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Reference: 1+1D paper-model representation of the Lambda-CDM cosmological model
I'm looking for a 1+1D (1 time + 1 space dimension) paper model of the current $\Lambda$CDM cosmological model; if possible, one which somehow respects the scales of geodesic spacelike distances at ...
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Is dark matter present in all galaxies?
The rotation speeds of nearby galaxies like M31 or our own milky way are determined by observations. And we know there that luminous mass does not explain the rotation curve. Are there any galaxies ...
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How does one obtain the formula for the differential cross section for direct detection of dark matter?
Several references (for instance, [Eq. 5 of this]https://arxiv.org/abs/1307.5955v5) quote the differential cross section for the direct detection of dark matter's recoil off nuclei as
$\frac{d\,\sigma}...
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How did Zwicky discover dark matter?
According to Wikipedia Zwicky used "virial theorem" to discover the gravitational anomaly in the Coma Galaxy cluster. But I also remember reading that he used Kepler's third law. Which one ...
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What is Singlet Fermion?
I encountered this term in the paper Singlet fermionic dark matter by Yeong Gyun Kim et al regarding Dark Matter. From my quantum mechanics knowledge singlet would refer to a singlet state which is a ...
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Theory of gravity and dark matter? [closed]
Most people assume that in order to have agreement between GR and the rotation curve of galaxies:
GR isnt correct
There is hidden matter which makes the galaxies rotate faster at their edges.
GR is ...
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Relic density and cross section
Is it possible that our annihilation cross section and relic density decreases if we add more dark matter particles having same mass the same portal couplings in the model ? if yes, what is the ...
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Could a fourth family of quarks and leptons account for dark matter?
In the early universe, could a family of quarks and leptons have formed an electrically neutral particle that is dark matter?
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If dark matter was created in the early universe and its formation released energy, is there any evidence of that energy in the cmb?
When atomic nuclei fuse, energy is released. Is there anything about the CMB energy distribution that suggests that dark matter could have formed from other particles that released energy?
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How can black holes possibly drive accelerating expansion of the universe?
(Potentially too broad, but all my questions are related to the paper in question.)
Recently there was an article published in Astrophysical Journal Letters that claims black holes "contribute ...
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Could Dark Matter be comprised of gravitational waves entrained in the bulk?
The evidence is strong that more massive galaxies have more massive Dark Matter (DM) halos (for example, Qi Guo et al, Monthly Notices of the Royal Astronomical Society, Vol 404 (2010)). Might this ...
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Axion vs. WIMP / Is Axion a WIMP?
What is the difference between an Axion and a WIMP?
A WIMP is just defined as a class of particles interacting via gravity and potentially via weak interaction (or a new force that is even weaker than ...
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+ spin Photons inside a right hand circularly polarized field with -spin photons outside of that field…”dark matter/energy”
As I understand it, If I am inside of a rh, circularly polarized EM field, there are only +spin photons inside the field: no -spin photons are admitted inside. The field inside serves to “filter” out -...
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Why modifying gravity to a fixed distance cant solve dark matter? [closed]
I quote Sabine Hossenfelder:
"A modification becoming important at a fixed distance however could never explain the observed rotation velocities for spiral galaxies, whose constant asymptotic ...
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Did galaxies spin differently 4, 5, 6 billion years ago?
Today I read that the Matter-dominated era ended 4 billion years ago, and now we're in the Dark Energy dominated era.
Obviously, light from galaxies far enough away would be from earlier in the ...
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Reference request for reviews on dark matter [duplicate]
Could anyone suggest some good reviews on dark matter? I'm looking for something recent. I'm interested in both theory and numerical approaches.
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Could it be possible that dark matter could one day be used as fuel by humans? [closed]
First we will have to know exactly what dark matter is. At the moment "dark matter" is a hypothetical type of matter that causes a specific gravitational effect. That is, we can measure an ...
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The slowing of expansion in the matter dominated era
On all the graphs of the inflation of the universe, the era dominated by matter is slowing the rate of expansion. With an intuitive explanation (for all you science communicators out there) could you ...
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Is MOND equivalent to Modified Gravity?
Usually, we consider two alternative models of dark matter: modified newtonian dynamics (MOND) and modified gravity (MOG).
My question is simple: can MOND be made equivalent to MOG or does it stand as ...
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$\Lambda$CDM's observations and the universe's matter content
It's known that the current value of the universe's total density parameter $\Omega_0=1$.
According to the $\Lambda$CDM model, the current density parameter of baryonic matter $\Omega_P \sim 0.04$, ...
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How wrong can we be about the gravity and dark matter? [duplicate]
Preface: pardon me if I make mistakes or use more common/imprecise language, I didn't study physics although I had few courses at university so I'm not completely lay.
If I understand it correctly ...
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Meaning of "coupling" in the context of Dark Matter decay?
I often hear the term "coupling" when people speak of a potentially decaying dark matter (DM) particle. I don't understand what a (hypothetical) DM particle should couple to when we consider ...
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Could dark energy and dark matter be the elusive luminiferous aether that was being searched for over 100 years ago
Is it suggested that dark energy and dark matter is the luminiferous aether that Sir Isaac Newton was proposing might exist?
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