Questions tagged [dark-matter]
Matter not observed directly but inferred to exist based upon its gravitational effects.
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What is meant by dark matter being non-relativistic and why is this?
What does it mean by dark matter being non-relativistic and why is it non-relativistic?
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Could the Many-Worlds-Interpretation influence the Galaxy-Rotation-Curves? [closed]
A Galaxy Rotation Curve shows the orbital speeds of stars vs. the distance from the galactic center. Measured Galaxy Rotatation Curves are curiously flat, meaning the outer stars orbit faster around ...
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1answer
46 views
Is there software to calculate/plot decomposed rotation curves from observational data (FITS, etc)?
I have observation data of galaxies (in FITS format). From the FITS data, I want to calculate & plot the decomposed rotation curves as pictured below. Is there a software package that will do that ...
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Assuming the announced $g-2$ experiment αμ discrepancy is mainly because a dark matter candidate, is this a quantum gravity induced effect?
The possible effectively extra added vacuum polarization by a dark matter candidate could account for the recently announced anomalous magnetic moment αμ measured discrepancy from the theoretical ...
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Fermilab's results and a fifth force [duplicate]
On today's news, it says that Fermilab have done measurements on the spin of muons and that they are measured to wobble faster than expected according to current physics theories.
Apparently this may ...
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2answers
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How much faster are the stars on the outskirts of galaxies going than they are 'meant' to as predicted by general relativity?
this is in reference to dark matter. I've look on the internet for this but I can't find precisely what I am looking for.
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1answer
54 views
What does it mean for CDM to “decouple from baryons”
I am currently working on my Final Year Project as an undergraduate, mostly intended to be a review of $\Lambda$CDM model and some of its modern challenges.
When talking about Cold Dark Matter I ...
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Dark matter … could it be somehow be sound waves? [closed]
I know that this sounds like a ridiculous question, silly even. But as they say, the only truly stupid question is the one not asked !
So how did I get to this thought.
Well I was reading stuff and ...
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1answer
33 views
How to understand the derivation of thermally averaged cross sections?
$$
\frac{d\langle\sigma_\text{ion}^{nl} v\rangle}{d\ln E_\text{er}}=\frac{\bar\sigma_e}{8\mu^2_{\chi e}}\int q|f_\text{ion}^{nl}(k',q)|^2|F_\text{DM}(q)|^2\eta(v_\text{min})\ dq
$$
How do I understand ...
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Has frame dragging been accounted for in galactic rotation curves?
This article explicitly takes frame dragging into account in calculating expected galactic rotation curves in the absence of dark matter, and appears to obtain very close matches to observed curves. ...
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Problem with the MadAnalysis
So I am trying to reproduce the result of arXiv:1404.1918 page 12, top-left figure 7 (attached figure) for signal-background of DM via top portal. In the paper the writers said that they use MadGraph ...
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1answer
62 views
Why is the distribution of Dark Matter in the Universe inhomogeneous?
As far as I know, there exist galaxies containing lots of DM and other galaxies with almost no DM at all.
This implies that the distribution of DM in the Universe is inhomogeneous. Do we have any idea ...
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1answer
102 views
Is there a theory of “dark mass” similar to but different from existing theories of “dark matter”? I.e. gravity without matter?
I'm curious to know if any mainstream theoretical physicists have theorized or spoken about the possibility of a theory of dark matter that doesn't involve any actual matter like hypothesized MACHOs ...
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2answers
71 views
Why a decaying dark matter?
I'm reading some papers (model, exp and model) that are dealing with decaying models of DM, why is it interesting? What are the signatures that this type of model can give to observe DM?
I am ...
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1answer
39 views
Is galactic gravitational lensing self-magnification big enough to contribute noticeably to the galaxy rotation curve problem?
Gravitational lenses magnifies the appearance of themselves, so in the case of a galaxy it looks bigger than it is. Thus the outer stars in a galaxy seems to have a higher tangential velocity.
For ...
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1answer
44 views
How are matter, dark matter and dark energy compared?
Matter, dark matter and dark energy "make up" 5%, 27% and 68% of the Universe. I can understand that matter and dark matter are comparable, but what does it mean that there is more than ...
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3answers
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Isn't dark matter just another fancy name and explanation for aether? [closed]
I always get crucified by this, but it is something that has intrigued me for a lot of time, before Michelson Moorley and Einstein there was this idea that there was an invisible "substance" ...
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Minimum mass of galaxies and dark matter
I have read somewhere that a relativistic dark matter particle can “free-stream” out of a primordial overdensity, and erase such densities within the comoving horizon distance, and that this can be ...
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Mass of Dark Matter Particle
I have heard that dwarf galaxy masses can be used to determine the mass of a dark matter particle. I have tried looking online for methods cosmologists use (https://cds.cern.ch/record/2702846, De ...
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2answers
60 views
Why does DM not being able to radiate energy keep it from total collapse?
I was going to post a question about gargantuan black holes being made from dark matter, but then I read some of the answers.. One question I do have though, is: "Why does it matter if dark ...
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1answer
88 views
From which dark matter made of? [closed]
Observations indicate that about 90 percent of the matter itself in the
universe is made up of dark matter. Exactly what kind of things dark matter made of?
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14 views
Proposed dark matter mass limits
A recent paper (arXiv version also available) proposes to derive dark matter mass ranges of $10^{-3} \sim 10^{7} eV$ for a singlet scalar, parity-violating pseudoscalar, or spin-2 candidate, $10^{-21}\...
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1answer
44 views
Why gravitational lensing appears circular?
I still remember the black hole photo but I know the coffee mug stain is actually the materials orbiting around it appears to be getting pervertedly blended 720 degree around the sphere, but then what ...
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1answer
50 views
What if dark matter occupied three other dimensions and it could only interact with our three dimensions through gravity and time? [closed]
I recently thought about dark matter existing in three other dimensions similar to ours but wasn't sure if it was logical. It would be of great help if someone would give me a clear insight into this ...
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Do gravitational lensing experience Doppler effect?
I watched dark matter explained by Perimeter Institute on YouTube and they used it as gravitational lenses, they also explained Doppler effect so we know how fast things are relative to us. I wonder ...
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1answer
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What sort of observations constrain the QCD interactions of dark matter?
Within our current limits of observation, dark matter (DM) is nonluminous i.e., it neither absorbs nor gives off electromagnetic (EM) radiation. This tells that DM is electrically neutral having no EM ...
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Self-interactions in Dark matter
I read that Self-interacting dark matter can resolve the cusp-core problem. Many of the papers introduce a scalar mediator $\phi$ and work out the abundance and other parameters.
I wanted to know when ...
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1answer
50 views
Does high energy limit of ionization process recover elastic scattering?
in my previous intuitive understanding, when some particle scatters with a bound state electron and leads to a continuous final state with recoil energy much larger than the initial binding energy, ...
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How robust is this 2020 measurement of the external field effect (EFE) in MOND?
There's a paper from a few months ago that claims to have measured this unique Modified Newtonian Dynamics (MOND) effect at high significance. The result seems very interesting:
The effect is unique ...
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0answers
34 views
What properties of dark matter can we derive from each of the available methods for probing the physics of dark matter?
This is probably a long shot but it's worth trying. My question is the following:
What properties of dark matter can we derive from each of the available methods for probing the physics of dark matter?...
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What exactly is dark matter? [duplicate]
Astronomers have shown that the objects in the universe from galaxies a million times smaller than ours to the largest clusters of galaxies are held together by a form of matter that is not what we ...
3
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1answer
49 views
Why don't cosmological observations tightly constrain cross-sections for direct detection of dark matter?
A reasonably recent review of dark matter detection is given by Liu et al., 2017, https://arxiv.org/abs/1709.00688 . I've reproduced their figure 1 below.
The cross sections on this graph span 13 ...
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1answer
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How could I calculate the circumferential velocity of stars in an idealized spherical galaxy from the distribution of mass through that galaxy? [closed]
We will assume that the galaxy is a sphere where stars orbit around the center on different radii. Since there are so many stars, we will not deal with individual stars, but we will assume that the ...
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Does dark matter interact with baryonic matter only through the gravitational field? [duplicate]
Do I understand correctly that dark matter fields are interact with baryonic matter only through the gravitational field? In this case, how can it be registred at all if it does not interact with the ...
2
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1answer
55 views
Can the gravity of one entire galaxy slow down an astrophysical jet emitted from its central black hole?
Let say we are talking about our Milky way and Sagittarius A* emitted a astrophysical jet. If the galaxy was 150 000 ly wide would its gravity with dark matter included eventually slow down that jet ...
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1answer
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Are Dark Matter and Antimatter “states” of matter? What broad category do these fall into?
This question is more to do with what matter is and what matter is not.
We know that there is something called matter, which is basically everything we see around us. 17 fundamental particles make up ...
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1answer
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Will spiral galaxies collapse when expansion of the universe isolates them from the rest of the universe? [closed]
If a galaxy gets isolated when the speed of the expansion of the universe exceeds the speed of light, will it collapse? The rotation of a spiral galaxy prevents it from collapsing due to gravity. So ...
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2answers
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Why can't Dark Matter be curvature without a proximal mass source? [closed]
I don't understand why Dark Matter or MOND/"gravity works different on bigger scales" are the only options to explain the observational data.
Why can't it just be curvature without a "...
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4answers
93 views
Why can't dark matter lose energy by gravitational waves and collapse into itself?
Because of lack of electromagnetic induction, dark matter can't lose its gravitational potential energy. That is preventing it from collapsing like an ordinary matter cloud in space.
But why can't ...
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1answer
40 views
Dark standard model linked though Higgs
is it possible to have a dark std model (ie image of the std model) linked to the std model only through the Higgs? That would allow dark matter condensation, dark galaxies, stars, planets and biology....
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1answer
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Infinities of Mass, Energy, & Velocity
My layman's understanding is that photons are particles having 0 mass, which is why they are capable of moving at c (lightspeed). Does our current model of particle physics postulate the existence of ...
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2answers
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How can we know the velocity curve past the cut-off radius of visible matter in a galaxy?
I am trying to understand a typical explanation for the need of a dark matter halo in galaxies. The rotational velocity of stars around the centre of a galaxy seems to be constant past a certain ...
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0answers
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Possibility of reaching equilibrium starting with a nonequilibrium initial condition in the early radiation-domination
Update after @knzhou's comment
If in a theory, the coupling of the dark matter (DM) field to the Standard Model (SM) fields is small enough, the rate of interaction of the DM particles in the ...
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Hydrogen-One (HI) Image and R-band
In the paper below, on page 3, it says "In the lack of HI image, we use the r-band b/a ratio to correct for the inclination". Am I correct in thinking that what this means is that if we ...
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2answers
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Single galactic proof of Dark matter?
I've heard tell that many galaxies have visible mass profiles which do not match up to a predicted Gravitationally Newtonian velocity distribution. Can anyone here find me an accessible paper of an ...
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3answers
67 views
What's stopping stars in galaxy from traveling at infinite speed?
The dark matter in galaxies causes the starts to orbit with a higher orbital speed. Now, assuming that there is a constant force from the dark matter on the starts, there should be constant ...
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2answers
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Might the Kaluza-Klein scalar provide a solution to the dark puzzles?
Kaluza-Klein theories of a five-dimensional spacetime yield not only the equations of general relativity and electromagnetism, but also a scalar field. This scalar field, sometimes quantised as the ...
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1answer
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Shape of exclusion plots of WIMP
What is the reason why the exclusion plots of WIMP experiments have that "U" like shape? And what sets the minimum of the curve?
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2answers
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Research in next decade on dark matter: sky surveys vs particle detectors
The next decade is very promising for cosmology as new surveys such as SPHEREx, Roman, Euclid, DESI which will shed light on inflation, dark matter/energy and more. At the same time there are particle ...
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1answer
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Why dark matter scales in the same way as the ordinary matter?
How do we know that the energy density of dark matter in the Universe scales as that of ordinary matter in the expanding Universe? Is it a guess?
