Questions tagged [dark-matter]
Questions about astrophysical observations, experimental searches, and theoretical models related to dark matter and its quanta.
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How to test for possible negative mass of dark matter?
What is the phenomenology of how to test if dark matter has possibly a negative mass (WP negative mass) in particle physics experiments, cosmology or astrophysics?
I lately came across this ...
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Could dark matter be just a gravitational effect of dark energy?
I'm wondering if we just looking at the two sides of the same coin and if there is actually a correlation of DM with DE?
Is it possible that DM just to be a gravitational effect (or an effect that ...
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How To Interpret Cross-Section vs. WIMP Mass Graph?
I'm a bit confused about how to interpret experimental data when it comes to dark matter. For example, in this figure from the XENON1T experiment, is it correct in saying that the upper bound for the ...
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Can ultralight dark matter particles be a massless relativistic field if they belong to a hidden dark sector?
Usually, we believe that dark "matter" is fermionic. My question is simple: is there any reason why a SM-inert massless unknown boson could NOT be the thing we know as dark matter if it only ...
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Dark matter and un-smoothness in spacetime [duplicate]
Since dark matter currently is only observable with its gravitational effects and nothing else can we theorize that dark matter is only non-smoothness in spacetime that has been there from the Big ...
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Does magnetism play a role in the formation of galaxies?
Forgive my ignorance as I know next to nothing about physics. From my layperson's understanding, galaxies are formed primarily by the interaction of gravitational forces of stars and planets, however, ...
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How do BAOs provide evidence for dark matter?
So far my understanding of BAOs is that they are a relic of the old universe formed by the freezing of acoustic density waves in baryonic matter as the universe entered the recombination epoch. These ...
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Does loop quantum gravity explain the dark matter effect without dark matter?
Does loop quantum gravity explain the dark matter effect (the rotational curves of the galaxies, the increased velocitoes of galaxies within galaxy clusters) without using dark matter?
As far as I ...
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$Ω = ρ/ρ[c]$, so although near to 1, for an accelerating expansion $Ω$ must be below 1. What's its value?
$Ω$ is taken to have different components - ordinary matter, dark matter, dark energy. But because it is expressed in relation to the critical density for attractive gravity, it seems that omega is ...
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Why is the ratio of dark matter to normal matter larger in galaxies than the cosmic average?
There seems to be a discrepancy between the ratio of dark matter to normal matter in the Universe (about 5 to 1 according to $\Lambda$-CDM) and the ratio of the average dark matter halo mass to the ...
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Why is the idea that dark matter consists of black holes unpopular? [duplicate]
Pryamvade Nataraja is convinced that dark matter is just trillions of black holes. Primordial black holes. James Webb will try to find out more. Sounds pretty plausible. I think she's right. Why not? ...
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Exclusion plots
I am having issues in reading exclusion plots like the one in the picture below (It is a plot regarding WIMP searches). What does the lines from various experiments (such as CRESST or LUX) mean? I don'...
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What does it mean for fluctuations to be constant over a range of physical scales
I'm self taught when it comes to physics/math, so apologies if this is a naive question.
While reading Barbara Ryden's Into to Cosmology Ch8 on CMB (Section 8.5), she says that for physical scales ...
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Why do we need hot dark matter?
Data on galaxy rotation curves suggested that not all the mass in the galaxy is accounted for and we can't observe them directly but remind me again why we need hot dark matter in the first place? ...
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Is it possible that the Dark Matter is not exist, but the spacetime itself rotating with a galaxy inside it?
Is it possible that a region of spacetime rotating with any objects inside it? In this case we don't need a dark matter to explain why distant stars have so big orbital speed. They moving with normal ...
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Mirror Matter Gravitation Interactions
I was reading the Wikipedia page on Mirror matter and I was puzzled by one of the statements in the article:
Mirror matter, if it exists, would need to use the weak force to
interact with ordinary ...
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Are heavy or light nuclei used in the direct detection of dark matter?
My understanding is that recoils of light nuclei are easier to detect as they recoil with greater energy, however is the interaction cross section not much smaller, meaning interactions are much less ...
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Which 1-loop Feynman diagrams are possible from this Lagrangian interaction term?
$$
L_{int} = g \bar{L} \cdot \tilde H N
$$
Where $g$ is the Yukawa coupling constant, $L$ is a lepton doublet, $H$ is the Higgs and $N$ is a right-handed neutrino. I think that at tree level only $\...
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In a freeze-out model, how does the number density of dark matter vary over time and why? [duplicate]
How does the number density of dark matter change over time in a freeze-out model, and why is it this way? My guess is that the number density decreases at the start of the universe until the ...
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Right-handed neutrinos Lagrangian and drawing Feynman diagrams from it
The Lagrangian for the right handed neutrino field is:
$$
L_{\nu} = y_{\alpha i} \bar{L_{\alpha}} H^{\dagger} N_{i} + m_{i} \bar{N^{c}_{i}N_{i}}
$$
With $ L_{\alpha} $ being the left-handed lepton ...
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Do counter rotating galaxies have dark matter?
Have counter rotating dark matter galaxies been observed?
Counter rotating galaxies, you may already know, are galaxies where some stars or arms rotate in one direction and other stars or arms rotate ...
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Is there data regarding the large-scale density (mass/volume) of “dark matter plus ordinary matter,” as a function of time?
Here, large-scale means (conceptually) the known universe. Hopefully, the data runs from (perhaps somewhat after) the Big Bang until now. Pointers to such results would be appreciated.
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In what type of trajectory do the Magellanic clouds move through our galaxy?
In what type of trajectory do the Magellanic clouds move through our galaxy? Can be estimated is it a elliptical, parabolic or hyperbolic trajectory? Although it may be a problem due to dark matter ...
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What does the "weak scale" mean?
In dark matter research, one of the properties of WIMPs is that "Interactions only through the weak nuclear force and gravity, or possibly other interactions with cross-sections no higher than ...
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Does Normal matter also include anti-matter and engery?
We have studied approx 4.6% of normal/ordinary matter in the universe and everything till now we observed are a part of this 4.6%
I always have doubt. this 4.6% include all the matters and energies ...
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What is the smallest scale at which the effect of dark matter can be observed? [duplicate]
Dark matter is primarily postulated in the context of large scale things e.g. spiral galaxies, in order to provide additional forces where vanilla gravity doesn't seem sufficiently strong to explain ...
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Can there particles which do not interact with matter at all?
Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. They are proposed to have very weak interaction with ordinary matter ...
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Axions and magnetic field
From what I know about the hypothetical particles "axions":
Axions are candidates to be cold dark matter particles
Dark matter interacts only gravitationally
Some experiments use strong ...
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Can we detect evaporating micro black holes?
The energy released by an evaporating black hole in its last instants (of duration $t$) is equal to
$$E = \sqrt[3]{\frac{t \hbar c^{10}}{ 5120 \pi G^2}}$$
As the math shows, most of the black hole's ...
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Gravitational binding energy as alternative to dark matter?
Pondering this question: Casimir effect and negative mass
and, in particular, the response of John Rennie "as the mass of any bound system is slightly less than the mass of its parts" I ...
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Galaxy filaments data access
I'm a PhD student in applied mathematics seeking to analyze geometric structure of galaxy filaments and walls, specifically the curvature and branching nature of the filaments and walls. I'm curious ...
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Dark matter/dark energy in Einstein's equation as manifestations of entropy production
It is well known that pressure adds a contribution to the gravity sources in Einstein's equation. That contribution is unknown in Newton's theory. What about entropy itself, or more precisely the ...
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What does "Position Reconstruction" mean?
What does "Position Reconstruction" mean in the context of Dark Matter detection? Specifically see e.g. the title of arxiv:1112.1481. Does it refers to an actual position in the dark matter ...
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If neutrinos are majorana fermions, does that mean any massive, weakly interacting majorana fermions will decay into neutrinos easily?
In particle physics, Dirac fermions are protected by conserved quantum numbers (electric charges, color charges, etc.). As a result, Dirac fermions can only annihilate with their antiparticles, and ...
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Does gravity affect dark matter?
On this photo the red color is ionized gas and a blue color is a fark matter. We see the shockwave on gas but the clouds of dark matter move through each other without any interactions. The dark ...
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Vacuum energy and dark matter
Vacuum energy can only be measured indirect. It is often discussed in the context of dark energy. The cosmological constant can be written as vacuum energy and vacuum pressure in the stress-energy-...
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Question about dark matter/energy and other dimensions
According to drummer and lyricist Henrik Ohlsson, the title Dark Matter Dimensions refers to the "appreciation and acknowledgement of the unseen worlds and dimensions, because without the ...
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Is Dark Matter in Motion?
What is known about the motion of dark matter, especially in galaxies?
It seems as though a particular distribution of dark matter might be required to cause the very flat galactic rotation curves ...
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Could the hypothesis of regular matter converting into dark matter help to find out what the dark matter is? [closed]
Could the hypothesis of regular matter converting into dark matter (Dark Matter from Exponential Growth, free version available from the arXiv with a rather different title) help to find out what the ...
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About the spatial distribution of vacuum energy around strongly gravitating objects in the galaxy
We know that the distribution of vacuum energy is spatially uniform. But we also know that it couples to gravity.
Anything with energy, such as a beam of light is affected by the gravitational field ...
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How observable is the "macroscopic" dark matter candidate?
I was recently introduced to the dark matter candidate known as "macros," which are theoretically made up of macroscopic clumps of matter rather than of an elementary particle. These ...
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Could quantum gravity be explained via the use of a "gravitational charge"?
Could gravity be explained as the existence of a "gravitational charge", acting similarly to an electromagnetic charge but where like charges attract and opposite charges repel? A graviton ...
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Axions approaching thermal distribution
I am reading Sikivie's paper on Axion Cosmology. I have the equation:
$$\frac{\mathrm{d}}{\mathrm{dt}}[R^3(n_a^{th}-n_a^{eq})] = -\Gamma R^3(n_a^{th}-n_a^{eq}) \tag{1}$$
where $R(t)$ is the ...
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Inverse momentum transfer in dark matter interaction
I'm reading papers about direct detection of dark matter and couldn't understand the term 'inverse momentum transfer'. Could someone please explain What the 'inverse' momentum transfer in the dark ...
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Newton's Law of Gravitation and dark matter [closed]
Before the days of Einstein the observation that light incident to the Earth's surface appears to be constant no matter whether the transmitter is travelling away from the earth or towards the earth ...
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Could quantum vacuum polarization increase GR frame dragging beyond the predicted values and therefore replace DM explanation of galactic rotation? [duplicate]
image source credits:David Butler
This anomalous speed rotation distribution of galaxies is today mainly contributed to Dark Matter.
However, since a definitive experimental measurement and ...
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Can Vera Rubin's findings be explained by a distribution of charge?
Vera Rubin found that the rotational velocity of galaxies is much greater than expected at greater distances from the center. Gravity from an invisible mass is assumed to account for this measurement. ...
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Dark Matter/Energy & Space-Time [closed]
After searching for quite a while for a minimalist approach to explaining Dark Matter as well as Dark Energy, unfortunately without much good, I decided I may as well help fill the explored paths, or ...
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Photons momentum and dark matter
Since moving photons have momentum, am I right to suppose that light from stars is able to interact with (and disperse, if intense enough) clusters of dark matter?
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How do I prove this integral solution in terms of modified Bessel function?
I came across this equation while studying about Dark Matter relic density but I can't seem to prove it.
In the early universe, the number density of dark matter in the thermal bath is approximately ...
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