Matter not observed directly but inferred to exist based upon its gravitational effects

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59
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5answers
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If dark matter only interacts with gravity, why doesn't it all clump together in a single point?

I'm a complete layperson. As I understand, dark matter theoretically only interacts with the gravitational force, and doesn't interact with the other three fundamental forces: weak nuclear force, ...
29
votes
6answers
2k views

Why isn't dark matter just matter?

There's more gravitational force in our galaxy (and others) than can be explained by counting stars. So why not lots of dark planetery systems (ie without stars) ? Why must we assume some undiscovered ...
1
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3answers
183 views

Does Dark Matter Exert The Same Gravitational Force As Ordinary Matter?

I have read through this Wikipedia article on Dark Matter and it contains references to the methods used to demonstrate the existence of dark matter. A galaxy rotation curve is a plot of the ...
-5
votes
1answer
86 views

Could Dark energy and Dark matter just simply be a warping of spacetime? [closed]

Why do most theories about what Dark energy and Dark matter is make it so that these substances (or not) need to be some kind of undiscovered particle? Would it be possible for Dark energy to simply ...
0
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0answers
38 views

Could dark matter annihilation prolong the stellar era?

I wonder, if we assume that dark matter actually exists, and it is WIMPs, and it's annihilate to fermions and W/Z bozons, which decay/combine into protons, neutrons and electrons and finally recombine ...
0
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1answer
42 views

Is it possible that cosmic ray particles and neutrinos account for a significant portion of dark matter?

Sounds a bit naive but I read somewhere that neutrinos were thought to account for dark matter to an extent and I think Zwicki came up with the idea before cosmic rays were announced (not sure though)....
5
votes
1answer
57 views

Need help with determining the total mass using the NFW profile

My review assignment has a question that asks us to use the Navarro–Frenk–White (NFW) profile to find total mass in the galaxy using $$\rho(R)=\frac{\rho_0}{1+\frac{R}{R_c}}$$ then taking a triple ...
2
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3answers
80 views

Can black holes grow via accretion of dark matter particles?

I'm assuming that the answer to the question in the title is a resounding yes. Since Baryonic matter and dark matter interact via gravitational forces. If this is the case how is information not lost ...
22
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4answers
3k views

How did the universe shift from “dark matter dominated” to “dark energy dominated”?

In order to get dark energy to dominate, wouldn't you first need another form of energy to push the expansion until dark energy could dominate? Otherwise I don't understand how the universe could ...
0
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0answers
30 views

Lagrangian Interaction Type and Spin-Dependence

So I'm transitioning from reading particle physics books to the literature, specifically as it pertains to dark matter models. In this case I'm talking about t-channel DM-nucleon scattering. They ...
0
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0answers
67 views

Why is Dark Matter not simply explained by QED

My understanding is that Dark Matter needs to exist to explain the mass of the universe -- that is, all the observable matter in galaxies are not sufficient to explain the gravitational behavior -- ...
5
votes
1answer
111 views

Relation between dark matter and supermassive black holes located in the center of galaxies

This research (see press article and technical paper), conducted on 3000 elliptical galaxies (which are typically galaxy merger results), reports finding "distinct relationship between the mass of the ...
1
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0answers
16 views

Form factor and EFT form factors for an interaction of a WIMP and a nucleon

On the third paragraph(right column) of page 1 of the paper, http://journals.aps.org/prc/abstract/10.1103/PhysRevC.89.065501, it says, "Because the momentum transfer in the scattering is large ...
2
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1answer
43 views

Do satellite galaxies have the same proportion of dark matter as “ordinary” galaxies

My question is relatively straightforward: Do we know if satellite/ dwarf galaxies contain the same proportion of dark matter to ordinary matter as "regular" sized galaxies? The Milky Way, for ...
-1
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0answers
17 views

Warm and Hot dark matter density profiles

for Cold dark matter, density profiles are well known and easy to find information about - NFW,Burkert,Einasto, and others. but for some reason i couldn't find explicit expressions for the density ...
2
votes
1answer
80 views

Is a nearby parallel universe still in use as an explanation for dark matter?

Is the theory which explains dark matter as the effect of a nearby parallel universe still used as an explanation for dark matter, or does this theory already lie on the pile of forgotten theories?
7
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1answer
69 views

Integrated Boltzmann equation for dark matter

In Dodelson's book, the equation for a scattering process $ a + b \Leftrightarrow c + d $ is given as \begin{align} a^{-3} \frac{\mathrm d (n_a a^3)}{\mathrm d t}&=-n^{\text{eq}}_a n^{\text{eq}}...
6
votes
1answer
111 views

Was the matter-energy content of our universe always distributed in the same ratios?

Currently, Dark energy (68.3%) and Dark matter (26.8%) together constitute about 95.1% total matter-energy content of the universe while only 4.9% is ordinary baryonic matter. Was this always the case?...
5
votes
4answers
668 views

Theory that gets rid of dark matter/energy

Is there any physics theory that either groups together gravity and dark energy/dark matter or eliminates dark energy/dark matter by modifying standard understanding of gravity or any force? If so, is ...
1
vote
2answers
130 views

Relativity and Galaxy Rotation Speed

If time travels slower nearer gravity wells, why can't the galaxy rotation speeds being faster on the outer edges than the inner areas be explained by relativity? What necessitates dark matter?
1
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0answers
39 views

How do funnels hinder (help?) detection of dark matter?

I came across some a new (to me) bit of terminology at a seminar recently. In the context of dark matter scattering off of atomic nuclei (but I think it may apply more generally for any particle ...
-3
votes
2answers
55 views

Dark Matter vs. Mass from Kinetic Energy

I was thinking about dark matter, and was wondering if the extra mass due to kinetic energy has been taken into account. Here's what I mean: let's talk about any cosmological object that is known to ...
4
votes
1answer
256 views

What is the difference between the Big Bang Model and the Λ-CDM Model?

If I'm going to write about "The Consensus Model of Cosmology" should I include Big Bang Model or should I go with just the $\Lambda$-CDM Model?
1
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0answers
28 views

How is mass of observable universe calculated? [duplicate]

How is even mass of earth known ? How do we get to know them? Whilst I was studying about dark matter it was listed about 'mass of observable universe' and density and so on...so what is the procedure?...
0
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0answers
44 views

Dark matter from general relativity? [duplicate]

We know that there is dark matter due to the observational orbital velocities and mass to light ratio not matching that of expected ones. However the expected orbital velocities of stars in the Milky ...
5
votes
1answer
69 views

What's the evidence, if any, for some local concentration(s) of dark matter in some region(s) smaller than a galaxy?

What's the evidence, if any, for some local concentration(s) of dark matter in some region(s) smaller than a galaxy? Galactic-sized - or larger - gravitating halos seem to get all the attention. I'm ...
15
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5answers
2k views

Dark matter and dark energy references

I've been looking for questions about dark matter, and I've read some very interesting answers. However, I desire too look into it deeply. This is not actually a question. I'm asking the community ...
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votes
1answer
226 views

What is dark matter? Also what is dark energy? I am not duplicating it put just want to write as an article for helping others [duplicate]

Today one of the greatest questions coming up is what is dark matter. also what is dark energy. we don't know much about it still!!! I have tried to bring some light on this question. To prevent ...
1
vote
1answer
43 views

What size of object does the peak of the cosmological power spectrum correspond to?

The title almost says it all, but to flesh it out more, what is the size a sphere corresponding to the peak in the cosmological power spectrum (Figure 2: https://ned.ipac.caltech.edu/level5/Sept11/...
11
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1answer
227 views

Why hasn't warm dark matter replaced cold dark matter as the standard model of cosmology?

The $\Lambda\rm CDM$ (cold dark matter with cosmological constant) is the current standard model of cosmology because the model comes with a long list of phenomena successfully explained by it. ...
0
votes
2answers
129 views

Higgs boson and dark matter.

In the standard model the Higgs boson gives the mass to other particles, but in the Universe we know that the 80% of mass is in form of dark matter, that is not constituted by known particles. The ...
0
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0answers
15 views

Shouldn't HDM drain photons energy?

Hot dark matter (HDM) would be made from very light, fast moving particles. Such particles could not possibly be gravitationally bound to any structure, but rather would be dispersed all across the ...
4
votes
1answer
83 views

Did LIGO detect dark matter?

Which is the title of this preprint They claim that: We consider the possibility that the black-hole (BH) binary detected by LIGO may be a signature of dark matter. Interestingly enough, there ...
2
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1answer
66 views

Where did all the photon energy go?

From the wikipedia page on dark energy, in reference to the total mass-energy of the universe: The mass–energy of dark matter and ordinary (baryonic) matter contribute 26.8% and 4.9%, ...
2
votes
0answers
25 views

What sets the lower mass limit for dark matter dominated structures?

Large galaxies appear to be dominated by dark matter, as do dwarf spheroidal galaxies with masses of perhaps $10^6 M_{\odot}$. But (as far as I'm aware) there is no evidence for dark matter in ...
0
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0answers
22 views

What are some good papers on the topic of dark matter that you would recommend? [duplicate]

I just finished off my BSc in physics a few months back and looking to learn more on the topic of dark matter. The topic of dark matter combines two of my favourite subjects particle physics and ...
1
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0answers
19 views

Galactic Rotation Curve Calculation

Can anyone give the list of formulas used for plotting the Galactic Rotation Curves? I mean, is there only the formula for linear velocity or is the formula for the gravitational potential also ...
3
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1answer
145 views

Reference request: dark matter and $f(R)$ modified gravity

Could someone please explain briefly or refer me to an article or manuscript that shows how $f(R)$ modified gravity theories can be used to explain the problem of dark matter, particularly the galaxy ...
38
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4answers
7k views

How do we know Dark Matter isn't simply Neutrinos?

What evidence is there that dark matter isn't one of the known types of neutrinos? If it were, how would this be measurable?
4
votes
4answers
213 views

Is it possible that dark-matter is composed of a large number of neutrinos from the big bang? [duplicate]

They seem to have all the properties of dark-matter (massive, with no electromagnetic interaction). Could it be that many of the neutrinos produced since the big bang have formed massive neutrino ...
-3
votes
5answers
288 views

Is dark matter really there? [closed]

Dark matter has been proposed to explain two phenomena - Uniform velocity curve of spiral galaxies Observed gravitational lensing. If something explains these two, would we still need dark matter?...
9
votes
2answers
92 views

CMB curly B-modes and dark matter

I raised a question a while ago regarding weak gravitational lensing of galaxies and the CMB. With all the fuzz with the BICEP2 data, I think it is time to raise even more questions about this amazing ...
7
votes
2answers
308 views

Would dark matter absorb gravitational waves?

Would the vast and seemingly diffuse clouds of dark matter floating around our galaxy (and most others) absorb gravitational waves? Is this perhaps why we haven't detected any yet?
3
votes
1answer
56 views

Questions about shape of dark matter orbits in spiral galaxies

Could someone please describe how are the proposed (calculated) orbits of dark matter? Are they exactly as those of baryonic matter (i.e. spiral), or they are different from those of baryonic matter? ...
3
votes
2answers
339 views

Do alternate theories for Dark Matter (like MOND) explain its effect on gravitational lensing?

For a long time, I was sceptical about the evidence for dark matter. To me, it seemed like a pretty big leap to make when we have no idea whether or not our current models of gravity should apply ...
35
votes
2answers
1k views

Are modified theories of gravity credible?

I'm a statistician with a little training in physics and would just like to know the general consensus on a few things. I'm reading a book by John Moffat which basically tries to state how GR makes ...
5
votes
3answers
684 views

How to explain two possible problems with dark matter

Can someone please answer how dark matter theory resolves/eliminates these two possible problems Dark matter, per my understanding, due to gravity, keeps moving, and due to its non-interactive ...
25
votes
5answers
3k views

Why doesn't dark matter affect planetary motion?

If the universe is made up of ~95% dark matter, and it interacts only gravitationally then why didn't Newton and Kepler discover it before ? Why does it show itself only in the radial velocity profile ...
0
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2answers
117 views

What is the amount of dark energy in the Universe, in joules?

I'm toying with an idea, and need absolute amounts of dark energy. I'd also like the same for dark matter. If these values are not estimated, why not?
1
vote
1answer
93 views

Virtual particles, gravity, and dark matter? [closed]

In Hawking's radiation, virtual particles respond to intense gravitational tidal forces with pairs being ripped apart. One crosses the event horizon and the other escapes. On the other hand, in ...