Questions tagged [dark-matter]
Matter not observed directly but inferred to exist based upon its gravitational effects.
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How far the galaxy's 'flat part of rotation curve' extends?
I know that the galaxy rotation curve doesn't obey general relativity and instead of decreasing, the star velocity remains constant which is shown by a flat rotation curve (rotation velocity v/s ...
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How to calculate the strength (“space force”) of dark matter within galaxies?
Let's first have a look at the observed speed within galaxies (source):
On the left side we can see the speed of celestial bodies within galaxies derived by gravity only (gravity is usually created ...
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Are there any databases for astronomical measurements (specifically amount of dark matter per galaxy)?
I was looking online for amount of dark matter in certain galaxies. I couldn't find any data on google. Does any one here know a trusted database which contains amount of dark matter in galaxies?
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Do the Bullet Cluster remnants prove that dark matter consists out of particles?
Some time ago the remnants of a collision between two collections of stars were discovered. These remnants are called the Bullet Cluster:
The color blue (non-visible in reality) represents the ...
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Cross correlations between 2 sensors - Approximation of a 2D + 3D synthesis
I am interested, in the context of my work, in the cross correlations between a spectroscopic probe (which gives a 3D distribution of galaxies with redshifts, which is also called spectroscopic Galaxy ...
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Is this equality based on the HDM true?
It is stated in Sterile Neutrinos as Dark Matter that in the HDM model: $$\frac{\mu^2}{m_s}= 92 h^2 \text{eV} \tag{1}$$
where $m_s$ represents the mass of sterile neutrinos and $\mu^2$ represents the ...
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1answer
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Does the Hubble constant depends on the model of the universe used?
I am writing an equation using the Hubble constant. My work is based on Dodelson's article on sterile neutrinos which uses a C$+$HDM model.In it a value of $h=0.5$.
But when reading the more recent ...
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Why would the damping factor of neutrino oscillations be negligible?
In this article the Boltzmann equation for the sterile
neutrinos is simpified to this form:
$$\frac{\partial}{\partial t} f_s (p,t) -H p \frac{\partial}{\partial p} f_s (p,t) \approx \frac{\Gamma_\...
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Can the velocity curves of galaxies be calculated (and corresponding to what's observed), without reference to observational data?
From this Wikipedia article:
Dark matter is a form of matter thought to account for approximately 85% of the matter in the Universe and about a quarter of its total mass-energy density or about $2....
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How can I convert a rate of black hole mergers into an estimate for the number density of black holes?
There's an estimate from the recent detection of intermediate-mass black hole mergers that there are roughly $0.13^{+0.3}_{-0.11} Gpc^{-3} yr^{-1}$ similar events a year.
I'm wondering how to convert ...
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Are there examples of dark matter at intra-galactic scales?
In articles I've read, evidence of dark matter (rotation of galaxies / gravitational lensing / galaxy collisions etc) is presented at galactic scales.
Are there examples of dark matter at smaller ...
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Which is the meaning of these masses?
When reading about the masses of neutrinos in the HDM (Hot Dark Matter) model of the universe, I came across the following equation:
$$\tag{1} \sum_i m_{\nu_i} = 92 \Omega_\nu h^2 \text{eV}$$
My ...
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Does any literature exist hypothesizing Strange Quarks as a candidate for Dark Matter? [closed]
Putting aside the more common suspects behind dark matter: neutrinos. A friend and I were discussing the possibility of Strange Quarks being an alternate candidate for Dark Matter.
If you're not ...
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Barred galaxies and the velocity at the tips of the bar
Ofcourse there must be something with the arrangement of masses, more precisely dark masses in barred galaxies but do scientists figure out are the velocities of stars along the whole circumference ...
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1answer
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Gravitational bonding energy of a galaxy
If most mass from a proton comes from the nuclear force's bonding energy between quarks that make-up this proton, why wouldn't most mass from a galaxy come from the gravitational force's bonding ...
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What is the relation between energy density ($\Omega$) and the number density of neutrinos ($n$)?
What is the numerical relation between energy density ( $\Omega_\text{s}, \Omega_\alpha$), and the number density of neutrinos (sterile - $n_s$ , active - $n_\alpha$)?
Background info that might help ...
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2answers
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Is it possible the many-worlds hypothesis explains dark matter? [closed]
To provide context for the title, is it possible that dark matter is just gravity from other 'branches' of the universal wave function that have split from ours, that are weakly interacting with the ...
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Higgs particles and Dark Matter particles
Usually, it is mentioned that the Higgs field IS the origin of mass for known fundamental particles.
If very heavy dark particles are found (heavier or much heavier than the top quark), should it mean ...
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Does dark matter follow all principles of regular physics?
Is dark matter bound by all the laws of regular physics?
i.e. laws of thermodynamics, speed of light, length contraction, mass-energy relation.
What about Newton's laws of motion (since all of Newton'...
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Looking for information on MACHOs (Massive compact halo objects)
I watched a program today on whether black holes were a part of what makes up dark matter. They could be up to 40% of what we consider as dark matter.
Is there a lay person version of what today's ...
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1answer
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Friedmann equation and model universes
I was studying Barbara Ryden book on modern cosmology, on it's 5th chapter, she introduces the following image:
This image summarises the general behaviour of the Hubble constant. I was wondering, ...
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Why is dark energy dominant between galaxies but not inside galaxies?
The ideas of dark matter and dark energy are mind blowing.
Why is it said that dark matter overcomes dark energy in galaxies but it loses the battle in intergalactic space? In other words, why is dark ...
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Why are axions considered cold dark matter? [duplicate]
Why are axions considered cold dark matter? They have a very low mass and if I'm not wrong they decouple before BBN, and in some models even earlier than neutrinos, they they should definitely be ...
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1answer
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Why doesn't dark matter collapse into a black hole? [duplicate]
Dark matter supposed to be affected only by gravity and no other force. At the same time, however, dark matter forms halos around galaxies, that become visible examining how galaxies and clusters bend ...
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1answer
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Dark matter distribution and solar systems
If it's lack interaction keeps dark matter from behaving like matter and ending up distributed like matter. Then why did it gather at the galactic gravitational well in the first place and why end up ...
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What is the mathematical implication of constant temperature and/or energy/momentum in the following identity?
Question:
What is the mathematical implication of constant temperature $(T)$, constant energy/momentum $(E)$ and constant ration of $(E/T)$ shown by the subscripts in $(1)$*?
$$T \left( \frac{\...
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Readings on Dark Matter [duplicate]
I am looking for introductions and reviews (papers or books) on the possible observation and the nature of dark matter. This book seems to be a good start, but I would be grateful for any other ...
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3answers
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Can photon be said to warp time only and not space? Can SR be modelled like GR, considering warping of temporal dimension only? [closed]
If we try to get closer and closer to a photon (i.e. get closer to speed of light), time slows down in a fashion similar to when we get closer and closer to a massive object. Are these two things ...
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Dark matter and gravitation
Dark matter does not interact with the electromagnetic force, however does interact with the gravitational force. Do we know if there are any big ‘clumps’ (like a star) of dark matter? If they exist (...
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Need help in deriving Boltzmann Equation for $3\to3$ scattering
This is the first time I am posting a question here, so please forgive me if I make any mistake. I am trying to derive the Boltzmann Equation for $3\to3$ scattering, which means there are 3 particles ...
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Could cosmological cold dark matter be a neutrino condensate?
What is wrong with the following?
Neutrinos are dark matter.
A neutrino condensate would be cold. (Often, neutrinos are dismissed
as being automatically hot dark matter.)
Cold neutrinos could be ...
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Cold neutrinos - how are they distributed?
Cold or slow neutrinos have non-relativistic velocities and hence very low energies. That makes them very difficult to detect. Answers to Where are all the slow neutrinos? make it clear that they are ...
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2answers
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Dark matter and velocity [duplicate]
We know that as the speed of an object increases, so does its relativistic mass.
But can it be said that dark matter may be due to the increasing relativistic mass of nebulae, stars, galaxies, etc. ...
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Cosmological consequences of the mass-energy content of gravitational waves
This paper published in 1969 indicates that a majority of the mass-energy of the universe may be contained in gravitational waves:
"Turning next to phenomena on a galactic scale, we find it ...
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1answer
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Rotational velocity due to Dark matter
I was wondering if we can predict the rotational velocity due to dark matter in this way:
Consider that we theoretically derived the rotational velocity of a galaxy ($v_{the}$). Then from experiment ...
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If the Holdom Force Exists what would be the spin of the force carrier of the Holdom Force?
I read about Mirror Matter.
Mirror Matter, if it exists, would be similar to ordinary matter, but with the chirality of some of the mirror particles being reversed. If mirror matter exists then there ...
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2answers
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What are ordinary mass-terms (of neutrinos)?
When reading the introduction to Sterile neutrino hot, warm, and cold dark matter I came across the following definition of sterile neutrinos:
We can define sterile neutrinos generically as spin-$\...
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1answer
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Is It Possible Right Handed Neutrinos Are Dark Matter?
Disclaimer: I am not a physics expert, just a teen with an interest.
I was watching a SciShow video, and they were talking about left-handed and right-handed neutrinos. The idea is that right-handed ...
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2answers
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Are ultra-cold neutrinos an option for cold dark matter? [duplicate]
Nobody hass seen cold dark matter. Are ultra-cold (non-relativistic) neutrinos, below 1 fK (femtokelvin), an option for dark matter?
This is a question about normal neutrinos - electron neutrinos and ...
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1answer
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Why is Fuzzy Dark Matter Cold?
Fuzzy dark matter (FDM) has a typical mass of $10^{-22}$ eV. With such a low mass, why is it typically assumed to be cold? That is, what keeps the FDM non-relativistic. With such a low mass, wouldn't ...
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2answers
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Why is dark matter and dark energy needed to explain why there's more and less gravity respectively than there should be? [closed]
Why is dark matter needed to account for that there's more gravity than there should be, and dark energy for that there's less gravity than there should be?
Obviously that can't be correct, but I'm ...
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1answer
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Do dark matter and dark energy have different physical laws from ordinary matter and energy? [closed]
What are dark matter and dark energy?
Do dark matter and dark energy have different physical laws from ordinary matter and energy?
Can string theory explain their mechanisms?
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Dark Matter Abundance and Being a Cold Relic
I was reading Longair its stated that,
"An important conclusion was that, if dark matter particles were as common as neutrinos and photons,their rest mass energies could not be much greater than $...
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2answers
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Unstable Dark Matter
Dark matter is generally considered to be stable or at least long-lived (age of the universe) and I understand that is necessary to have such abundance today. My questions are 3:
Is it 100% necessary ...
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Is dark matter paramagnetic/diamagnetic?
From my understanding, constrains on the interaction of dark matter with electromagnetic fields comes from the lack of scattering/absorption/emission of light.
But, do we know anything of its DC ...
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Are neutrinos and sterile neutrinos both dark matter candidates?
Are both neutrinos and sterile neutrinos candidates for dark matter?
In particular, why would "standard" neutrinos be a candidate for dark matter, since they interact with matter?
Why would ...
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What is the gas distribution in galaxies?
I'm fitting a number of galaxy rotation curves, and I need the density distributions of stars, gas, and DM. I know that the baryonic disk densities fall off exponentially (the characteristic radii can ...
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37 views
How are neutrinos massless? Could they or at least some of their forms be a potential candidate for Dark matter? [duplicate]
I am particularly new to this subject. Can neutrino physics be understood by a 10th grade?
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What do we know about the features of Dark Matter? [closed]
In 2020, how much information have we got about this matter? I'm just curious.
