Questions tagged [dark-matter]
Questions about astrophysical observations, experimental searches, and theoretical models related to dark matter and its quanta.
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Does neglecting dark matter solve the Hubble tension?
If the total mass of the universe is smaller than estimated by neglecting the gravitational pull of dark matter, the estimated expansion rate should be greater.
Does this consideration in the CMB ...
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Group velocity, phase velocity and signal velocity for axion like particles
In dark matter models of axion-like particles (ALPs), sometimes we get the field
$$\phi=2\phi_0\sin(m_\phi c^2 t/\hbar)\cos(k_\phi x)$$
This is like an stationary field with amplitude $\phi_0$ (in m/s ...
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Yang-Mills mass gap caused by gluonballs or because dark matter WIMPs?
Yang-Mills quantum field theory predicts the existence of the lightest massive Bosonic (i.e. integer spin) particle.
This massive Boson will be much lighter than the $W$ and $Z$ Boson and therefore ...
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Transplanckian energy magnetic monopoles in string theory/M-theory
I was thinking about transplanckian energy $E>10^{19}GeV$ magnetic monopoles in string theory and M-theory. Are they possible in Nature like the Dirac, 't Hooft Polyakov, Julia-Zee monopoles/dyons? ...
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Dark matter Thermal average cross section expansion
In many papers and books, including paper written by P.Gondolo & G.Gelmini in 1991, COSMIC ABUNDANCES OF STABLE PARTICLES: IMPROVED ANALYSIS, it is well known that for non relativistic gas, you ...
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Is there an spherical symmetric Einstein vacuum solution which has circular orbits with flat velocities? Or a proof that it cannot exist?
The Schwarzschild solution shows decreasing velocities with larger orbits - and needs help from dark matter or MOND to explain galaxies.
Apparantly no Einstein vacuum solution with flat velocities is ...
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What's the argument(s) against dark matter being "normal" baryonic dust?
So I just finished watching "dark matter is not a theory". An understanding I gleaned from it is that dark matter is observed from the discrepancy between the amount (or perhaps energy? in ...
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Why are dark matter and dark energy favoured over changes to our physical models? [closed]
I am instinctively skeptical of the existence of "dark matter" and "dark energy". Together, they strike me as being analogous to luminiferous aether -- something that was invented ...
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What if gravitation was the only force? [closed]
This is a follow up of Interactions within constituents of dark matter .
I wonder about dark matter, and, naturally, compare it with our observable world.
If gravitation would be the only force acting ...
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Is Dark Matter really invisible? [duplicate]
From what I understand dark matter is called dark since it cannot be seen in the universe.
My question is does it have to be invisible, as in to not interact with light ?
Could it be that dark matter ...
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Is the amount of dark matter per galaxy the same as you look back through time (further away from earth)?
In the hope that it may inform us about the development/evolution (if any) of dark matter over time, are there any differences (eg. in structure or concentration) in the dark matter at large radial ...
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What is dark matter? [duplicate]
My friend asked me about dark matter and started saying that it is likely to be another world made up of things we say dark matter and energy said that quantum fluctuations may be the cause of dark ...
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If we are sure dark matter is not modified space producing gravity can we spot an object deacceleration while moving through a dark matter cloud?
Can a moving object deacceleration caused by interaction with enviroment be measured while the object passes through a region populated by dark matter?
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"Penrose Functional Degrees of Freedom" ( PFDoF) as a source of dark mass
In his book "Fashion, Faith, and Fantasy in the New Physics of the Universe" Sir Roger Penrose mention ( referring to his older works and specially Penrose-Hawking Theorem) the possibility ...
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Why doesn't frozen-out dark matter annihilate later during structure formation?
The so-called freeze-out of dark matter is based on a homogeneous description. However, in the later stages of the universe, where structures form, it seems very likely that the reaction rate would ...
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Attraction between dark matter
Why does dark matter not attract other dark matter in space, and form a giant structure?
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General Relativity "doesn't quite work" without dark matter?
I am taking an astrophysics course, and my astro professor said that "we need to introduce dark matter because Einstein's general relativity doesn't quite work without it".
I wanted to ...
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Why isn't the "Dark Matter" in the Bullet Cluster supermassive black holes?
I've seen several videos that claim that the Bullet Cluster is evidence for Dark Matter. The general idea is that the gas is trapped on one side of the collision and the light-bending "Dark ...
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Is Dark Energy Taking Over?
First question, trying to keep it simple 😃
Because it's constant it grows in magnitude as the universe expands, whereas normal matter does not? Is this accurate as far as we know?
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Is shape dynamics capable of explaining dark matter?
I recently got introduced to the incredibly fascinating subject of Shape Dynamics: for example see https://arxiv.org/abs/1409.0105
Shape Dynamics uses conformal three-dimensional geometry to build up ...
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Interactions within constituents of dark matter
Inspired by Are the visible matter and dark matter separately segregated? I wonder if the constituents (I don't say particles, as we don't know) have actions and forces among themselves, that we ...
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Are the visible matter and dark matter separately segregated?
I am having difficulty in visualising dark matter. Dark matter does not interact electromagnetically. Dark matter is inferred gravitationally.
However it is not clear whether dark matter is present ...
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Can dark matter be isolated from baryonic matter?
The above is an image to test Verlinde's emergent gravity theory (2016, https://arxiv.org/abs/1611.02269). The research team observered galaxies and masses beyond, used gravitational lensing (y-axis) ...
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Which of Newton's shell theorems applies to a galaxy?
From this question I gathered that Newton came up with two sets of shell theorems, one for hollow spheres and one for solid. It was also said we should use the version inside a solid sphere to model ...
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Galactic Rotation Curves
While researching rotation curves, I've noticed a variety of velocity behaviors in different galaxies. In some, the velocity decreases, in others, it remains relatively constant, and in some cases, it ...
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Theoretically, is it feasible for the dark matter density to be constant and homogeneous, as dark energy is, and the two to be related?
I know that currently dark matter and dark energy are separate things, not related and one not deriving from the other. But if both are included in a generalized gravitation theory, the picture can ...
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How can I estimate the dark matter density for some specific galaxies by using the rotation curves?
I have rotation curve data (radius vs rotational velocity) for some specific galaxies. How can I estimate the dark matter density for those specific galaxies by using the rotation curves? Or is there ...
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Scalar Axion Field Amplitude Calculation in localised laboratory / Earth
This question concerns the paper "Axion Dark Matter: What is it and Why Now?", in the Appendix A.3 regarding equations related to the Axion Field.
It states that by the Friedmann Equation,
$$...
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Invisible decaying dark photon
I am interested in invisibly decaying dark photon to the dark sector.
Let's assume the particles in dark sector are dark photon ($\gamma_D$), dark matter (DM) , and long lived particle scalar ($\phi_D$...
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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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