Trio of physicists create computer simulation of dark matter using an empirical function

Jul 03, 2014 by Bob Yirka report
Tangled web. A simulation of gravitationally interacting dark matter particles in the Universe shows the stringy nature of dark matter, peppered with voids, over the largest distance scales. Credit: N. Hamaus/Paris Inst. of Astrophys. & M. Warren/Los Alamos National Lab, via Physics

(Phys.org) —Three physicists affiliated with several universities in the U.S. and France have built a computer simulation of the bubble-like voids that exist in dark matter which offers better density information. In their paper published in the journal Physical Review Letters, the researchers describe how their simulation showed that such voids have a wide range of sizes and ages with highest densities occurring in boundary areas.

Scientists still don't know much about dark matter—it's believed to make up most of the known universe (as evidenced by gravitational studies) and doesn't interact much with parts of the universe we can see, which of course, includes light. To gain a better understanding of it, researchers have been creating based on what is observable. Such simulations in the past have shown that dark matter is not uniform, in fact, if we could see it, it would look a lot like the inside of bones—lots of air pockets (voids) with boundary material between them. The simulations indicate that the voids in dark matter form as dark matter akin to a gas, collapses under its own gravity into sheets or filaments that form the boundary between the voids. They also have shown that there appears to be more void, than boundary. Some theories suggest that such structures gave rise to the parts of the universe we are able to see. In this new effort, the research trio has created a new that provides a better perspective on the size and shapes of the voids—focusing specifically on density profiles. Their simulation excluded matter that can be seen but did include dark energy.

The new simulation showed voids of various sizes and shapes as has been seen with other simulations—what was new with this simulation was that the team showed that the average density of reached its maximum in the walls that formed the borders between the voids. They also found that the spherical densities believed to exist at the center of the voids, applies not only to voids of all shapes and sizes, but to those that existed in earlier cosmic history. Interestingly, the researchers found they could fit the profiles empirically using just two parameters in a single formula.

Explore further: Cosmologists weigh cosmic filaments and voids

More information: Universal Density Profile for Cosmic Voids, Phys. Rev. Lett. 112, 251302 – Published 27 June 2014: journals.aps.org/prl/abstract/… ysRevLett.112.251302 . On Arxiv: arxiv.org/abs/1403.5499

ABSTRACT
We present a simple empirical function for the average density profile of cosmic voids, identified via the watershed technique in ΛCDM N-body simulations. This function is universal across void size and redshift, accurately describing a large radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. While we initially start with a more general four-parameter model, we find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, we derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In our companion paper [Sutter et al., arXiv:1309.5087 [Mon. Not. R. Astron. Soc. (to be published)]], the presented density profile is shown to be universal even across tracer type, properly describing voids defined in halo and galaxy distributions of varying sparsity, allowing us to relate various void populations by simple rescalings. This provides a powerful framework to match theory and simulations with observational data, opening up promising perspectives to constrain competing models of cosmology and gravity.

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katesisco
1.2 / 5 (17) Jul 03, 2014
Could it be as simple as comparing 'dark energy' to 'momoatomic gold?" After all this type of gold atomic arrangement is not 'seen' by normal chemistry methods as it violated the understanding of bonds.
Then the question would be, would it not, what causes our understanding of chemistry bonding to be insufficient?
What produces energy that creates a this separate structured world?

May I propose it is the energy similar to the energy put out by our monopole sun from its equator described in NASA a star with two poles. We, then, are the product of a dipole sun and unbeknownst by us live amid energy from the monopole sun, the energy put out in the period of what we euphemistically know as a delayed magnetic reversal.
J P P
4 / 5 (7) Jul 03, 2014
Looks like the bottom of my swimming pool.
Uncle Ira
3.9 / 5 (11) Jul 03, 2014
May I propose it is the energy similar to the energy put out by our monopole sun from its equator described in NASA a star with two poles.


Kate-Skippette you can propose anything you want to propose and what you proposing is about as weird as anything that has been proposed here so far. Why you would think that the sun wouldn't be a monopoly? There is only the one in our neck of the woods. Are you thinking there is another one hiding near by or something like that?
Whydening Gyre
4.6 / 5 (13) Jul 03, 2014
Could it be as simple as comparing 'dark energy' to 'momoatomic gold?" After all this type of gold atomic arrangement is not 'seen' by normal chemistry methods as it violated the understanding of bonds.
Then the question would be, would it not, what causes our understanding of chemistry bonding to be insufficient?
What produces energy that creates a this separate structured world?
May I propose it is the energy similar to the energy put out by our monopole sun from its equator described in NASA a star with two poles. We, then, are the product of a dipole sun and unbeknownst by us live amid energy from the monopole sun, the energy put out in the period of what we euphemistically know as a delayed magnetic reversal.

Hunh?!?
Torbjorn_Larsson_OM
5 / 5 (13) Jul 03, 2014
@katesisco: Gold is by definition mono-atomic as an element. Crystal lattices on the other hand, say of pure solid metal gold, are by definition not mono-atomic.

More pertinent here, dark matter do not form electromagnetic (electron mediated) bonds, as the name "dark" clearly expresses, but interact gravitationally. Whole different kind of interaction.

Your comment comes over as classic Dunning-Kruger, you have no idea what the physics is here and you don't seem to know that.
Torbjorn_Larsson_OM
4.7 / 5 (13) Jul 03, 2014
@JPP: _Very_ perceptive! When physicists predict the generic shape of filaments, not by detailed particle models but the generic physics, they derive them as caustics analogous to how light makes them at the bottom of a swimming pool. (But it's a 3D volume process vs a 2D surface one. Still, the caustics looks much the same.)

The seed density perturbations are quantum fluctuations in the inflaton field under inflation. The earliest, most expanded ones push the local universe out of cold inflation into hot big bang heating. The later becomes energy fluctuations, then mass density fluctuations as matter appears out of the cooling vacuum. And the particles in these moves randomly, as initiated by the fluctuations, such that caustics appears.

Susskind, goes through that in his cosmology lectures on youtube. (Google Stanford University if you are interested. Note that there are two series by now, you may want the later more up to date one.)
Torbjorn_Larsson_OM
5 / 5 (8) Jul 03, 2014
[ctd] IIRC he even uses the swimming pool example. It isn't too complicated. In swimming pools it is (more or less) randomized surface waves that refracts the photons in randomized directions. Caustics is where photons from different directions happens to meet (hence lighter streaks) at any one time at the bottom. (So forms a sort of projection.) When the waves move, so do the caustics move or appear/disappear.

Susskind has a 1D toy model that still pertains to both 2D and 3D caustics.
Torbjorn_Larsson_OM
5 / 5 (7) Jul 03, 2014
Oh, a difference between the light and the matter caustics is that gravitation "fixates" the latter. E.g. the first-time filaments and voids stick around, and the filaments form galaxies.
Mimath224
4 / 5 (2) Jul 03, 2014
Can someone help me on this. My understanding here is that,excluding gravitational effects, DM does not, or does very little, interact with matter/energy as we currently understand these. But do not the simulations indicate that it does interact with 'itself' thus forming sheets etc. Is this interaction expected to be completely gravitational or perhaps some kind of grav/(anti?)magnetic. That is to say, do the equations parameters for the simulation exclude one or the other or are both inluded?
DeliriousNeuron
1 / 5 (9) Jul 03, 2014
Good to see u chiming in Aunt Ira.

Computer simulations are crap. It makes for great story telling though.
Call me Skippy Auntie Ira, but u people really need to read up on the electric universe theory. Start observing with your eyes and quit making up words to "fit" broken theories.

There are plenty of recent videos on YouTube.
thermodynamics
3.7 / 5 (10) Jul 04, 2014
Just for background, the concept of monoatomic gold is a conspiracy/scam that preys on those with weak scientific background and who believe in magical things.

http://educate-yo...05.shtml

Just one more strange things that people believe in like the EU.

I don't know why so many of these nut cases show up on this site.
George_Rajna
1 / 5 (5) Jul 04, 2014
Dark_Matter_and_Energy: https://www.acade...d_Energy
Technico
1.8 / 5 (5) Jul 04, 2014
Looks like the bottom of my swimming pool.
This is actually a good point, which may be related to holographic theory. In this model the bulk of universe appears like the volume caustic projected with ripples at its surface. Unfortunately, this analogy points to weakness of holographic model too: such a projection can be applied only to the most subtle and most difficult to observe portions of Universe, like the dark matter filaments.
Technico
2.1 / 5 (7) Jul 04, 2014
In dense aether model the dark matter is driven with presence of observable matter in the same way, like the observable matter is driven with density of dark matter. They're in mutual equilibrium due to shielding geometry of dark matter formation. The dark matter emerges along the lines connecting the already collinear galaxies, where the longitudinal waves of vacuum are most enforced. When two or more such a lines intersects mutually, then the resulting density of dark matter may be so high, it induces a formation of a new galaxy at this place. The negative charge of dark matter gravity keeps the dark matter in finely widespread state. From general point of view therefore the dark matter helps to maintain the Universe homogeneous: it fills the holes in it like if the galaxies would be gigantic density fluctuations evaporating and condensing inside of it.
Technico
2.5 / 5 (8) Jul 04, 2014
The same effects can be observed at the undulating water surface: when some massive ball (or island) will stick out of it, the surface waves will be shielded with it at proximity (coastal shorebreakers), the longitudinal waves from underwater will be shielded at somewhat larger distance (turbulent underwater currents around islands). While the islands shield the coast against surf waves, the underwater tsunami waves may be actually attenuated with them instead. If you're a good sailor, you should have an experience with 2D analogies of dark matter already.
TechnoCreed
5 / 5 (4) Jul 04, 2014
@Zephir
Why did you create a new account when otero and Doiea are still active? This pretending game that you comeback to every time you are under influence is annoying everybody here, but most of all substance abuse is destroying you young man. Please seek help.
Dr_toad
5 / 5 (1) Jul 05, 2014
I don't think it's substance abuse. He has been insane for years. If it were progressive he'd have devolved to unintelligible grunts by now.

Oh, wait...
pete_davis_359
not rated yet Jul 06, 2014
"...and doesn't interact much with parts of the universe we can see, which of course, includes light. "

Includes light? I wasn't aware that we saw anything other than light.
otero
Jul 06, 2014
This comment has been removed by a moderator.
otero
Jul 06, 2014
This comment has been removed by a moderator.
Captain Stumpy
3.7 / 5 (7) Jul 06, 2014
If we would all use the matter of fact arguments and if we would all refrain of name calling and another subjective arguments, then the name of posters would become irrelevant
@otero-Technico-Zephir
not if they continually post pseudoscience and known debunked science like you do
Only at the forum composed of old farts blah blah blah the actual names of posters become necessary for to give some meaning their posts
unfortunately for you this is a science site, not a forum. these are comments sections after articles, not forum headers.

At least on a forum site there is usually a place for crackpots to go to, whereas here your only recourse is to disrupt any thread with your DAW crap-o-la... it is debunked! your religion is proven dead: http://arxiv.org/...1284.pdf

now go away or at least stick to REAL science
Benni
1 / 5 (3) Jul 06, 2014
......now go away or at least stick to REAL science


.........before preaching to others, you should first start practicing it, also your boatmate Ira.
Uncle Ira
3 / 5 (2) Jul 06, 2014
......now go away or at least stick to REAL science


.........before preaching to others, you should first start practicing it, also your boatmate Ira.


Does this mean you going to tell about the different equations this time? It should would be nice to see you do one of those things Bennie-Skippy here on the physorg, just so we know you actually know what they are. Oh yeah, some of those semi circle universes things would be good too if you aren't to busy to teach us some REAL science.
otero
Jul 06, 2014
This comment has been removed by a moderator.
Captain Stumpy
4 / 5 (4) Jul 06, 2014
it is debunked! your religion is proven dead
The measurements with microwaves can never lead to positive result of M-M experiment (even at the water surface the waves of the same wavelength http://i.imgur.com/yVXV43P.jpg
otero-technico-zephir
better go back and RE-READ that link...
it appears you missed a WHOLE LOT...

hopefully you will actually READ the link this time and see where you messed up... maybe ben-wa boy will explain it to you...if he can recognize real science
TechnoCreed
5 / 5 (4) Jul 07, 2014
@Zephir
Let me put it this way; old fart, if you consider a man in his fifties as such, have been stacking facts for years and is not going to argue with somebody who, for some reasons, is playing pretend. It is not that I find you unintelligent, it is just that I do not have any interest for that. I can appreciate a good comment from you, has you are much more grounded when you defend your political positions.

I think that the credibility one can have on an anonymous comment, still depend on the credibility of the poster. In that sense, yes your identity does matter and you have given a rough ride to yours for years. You see Zephir you interact on line with real people not with toys and it is important to give as much consideration to others as you are asking from them. Since you are asking for a matter of fact argument, here it is, playing games with others is a lack of consideration and can only bring you distrust and rejection.

If you do not like the Universe you are in, do not worry, you are not alone. I would much prefer Fred Hoyle's steady state Universe and deBroglie-Bohm quantum mechanics but here this is irrelevant. This is a GP comment board and accepted science is the topic; there is no paradigm shift to be created here. If you seriously want to contribute to science go for a PhD. Whenever I see somebody writing about his pet theory, I just scroll down.
Dr_toad
5 / 5 (3) Jul 07, 2014
Captain Stumpy, sorry I downvoted you. I was in a frenzy, downvoting the Idiot Wind.
Captain Stumpy
5 / 5 (4) Jul 07, 2014
Captain Stumpy, sorry I downvoted you. I was in a frenzy, downvoting the Idiot Wind.

not a problem.. it happens

especially with the proliferation of pseudoscience crackpots ...

Gawad
5 / 5 (3) Jul 08, 2014
Looks like the bottom of my swimming pool.


And so the physics in the bulk of your swimming pool is represented on the 2D membrane at its surface...errr, bottom ;^)
otero
Jul 08, 2014
This comment has been removed by a moderator.
skills4u
1 / 5 (1) Jul 09, 2014
WOW ! All this bickering back and forth is irritating....Do you all not realise by now that each is talking to a brick wall ?? Neither side is gonna convince the other side ! A famous man once said " Do not throw your pearls before swine, or they will trample them under their feet, and turn and tear you to pieces"
Captain Stumpy
5 / 5 (3) Jul 09, 2014
the appeal to authority logical fallacy ... You're essentially saying with it, that your thinking is fallacious.
@Jantoo-Sikla- otero-Doiea-Technico- zephir
Unfortunately you are wrong.
this is a nice delusion, however. Perhaps you wish it WOULD be this way, but it is not. Otherwise, even the worst, most disreputable character like, say, a known crack-head junkie with multiple arrests and convictions for drug related crimes, or even a known pseudoscience poster that continually supports fringe physics with no empirical data or reputable science... those people would be equal when giving depositions to the law, or in court as witnesses... however, that is NOT the case.
PAST HISTORY AFFECTS PRESENT IMAGE
Neither of the above would be a credible witness unless the case involved giving up the main dealer/supplier for the junkie or proving that the main crackpot conspired with said pseudoscience poster to defraud others...
and even then there would have to be evidence and lots of pro
Uncle Ira
5 / 5 (2) Jul 09, 2014
@ Captain-Skippy. I did not know where to put this so I stick him here. I tried to read one of those books you tell me about by the Sean-Carroll-Skippy. The one called "From Eternity to Here". I guess I am not ready for that one yet because most of it just make me more confused about some things in it that he talks about.

But I wanted to tell you about the another really good book I bought at the same time that was easy to understand and fun to read.

It's called "The Day We Found the Universe" and was written by the Marcia-Bartusiak-Skippette. It is more about the peoples and history of the astrophysics scientists about a 100 years ago learning about how big the universe is and the telescopes they used and all the arguments they had with each other about who was right about what they were seeing.

It is more the biography and history than the really complicated science stuffs so maybe you would not like him, but I thought it was one of the best books I read in a long time.
Scroofinator
1 / 5 (2) Jul 09, 2014
More pertinent here, dark matter do not form electromagnetic (electron mediated) bonds, as the name "dark" clearly expresses, but interact gravitationally. Whole different kind of interaction.


The crazy thing is we don't even know that GR is true, yet it's accepted as fact even though the "founding" of DM/DE proves it's inadequate. Blows MFM. We KNOW something is wrong, but we still keep grasping at straws trying to explain it. How many unobservable constructs do we need? Gravitons, DM/DE, Higgs Boson(still questionable), enough is enough already.

Do you think Einstein or so many others would have missed something so massive in the calculations? Or is it more logical we started with a flawed theory from the beginning? The only reason we don't take GR as fact now is because we have better telescopes then they did, and we saw the force from something we couldn't explain. That tells me F=MA doesn't translate perfectly to the celestial realm. Find a new explanation, not variable.
Captain Stumpy
5 / 5 (2) Jul 09, 2014
It is more the biography and history than the really complicated science stuffs so maybe you would not like him, but I thought it was one of the best books I read in a long time.
@Ira
thanks for the heads up... I will look into that one.
I like history just fine too... as well as other things. and I LOVE to read. I own more than 5000 and the library sometimes asks to borrow from ME... LOL no joke!

but seriously... I've not heard of that book : "The Day We Found the Universe" and was written by the Marcia-Bartusiak-Skippette
I will look it up. I always like a good read.
Here are some more for you to look for:
The Relativity of Wrong by-Isaac Asimov (GREAT book)
A Short History of Nearly Everything by Bill Bryson (and some of his other works too... he is pretty funny)

I will look around for more that you might like... If you ever go to http://www.sciforums.com
look me up. I am Truck Captain Stumpy there... you can get my e-mail address there too
then I can e-mail you more
TechnoCreed
5 / 5 (4) Jul 09, 2014
WOW ! All this bickering back and forth is irritating....Do you all not realise by now that each is talking to a brick wall ?? Neither side is gonna convince the other side ! A famous man once said " Do not throw your pearls before swine, or they will trample them under their feet, and turn and tear you to pieces"

@skills4u
Welcome to the Phys.Org comment board! Be advised that, whenever you enter a discussion related to cosmology or quantum mechanics, you are going to be confronted by S=K logW . The chaos you are observing is a strange mix of realists, instrumentalists, alchemists and, as if it was not enough, economists and luddites. Jump in and experiment the odd interactions between these free particles. ;-)
Captain Stumpy
Jul 09, 2014
This comment has been removed by a moderator.
skills4u
5 / 5 (2) Jul 10, 2014
TechnoCreed- Thanks for the welcome. I have been a long time reader of the boards, though I have just recently registered, so I am well aware of the "chaos".

Captain Stumpy- Tis a hard thing to change ones mind that that is already made up. Debate is good, but "yes it is/no its not" is not a debate.

I am a novice to science but I have an open mind (I hope). Some of it blows my mind, like earlier I saw a satellite image of the last hurricane and thought "wow ! that looks like a pinwheel galaxy !" I am still pondering that one :)

Captain Stumpy
Jul 10, 2014
This comment has been removed by a moderator.