Physicists measure the loss of dark matter since the birth of the universe

December 28, 2016
The discrepancy between the cosmological parameters in the modern Universe and the Universe shortly after the Big Bang can be explained by the fact that the proportion of dark matter has decreased. The authors of the study could calculate how much dark matter could have been lost and what the corresponding size of the unstable component would be. Researchers may explore how quickly this unstable part decays and say if dark matter is still disintegrating. Credit: MIPT

Russian scientists have discovered that the proportion of unstable particles in the composition of dark matter in the days immediately following the Big Bang was no more than 2 percent to 5 percent. Their study has been published in Physical Review D.

"The discrepancy between the cosmological parameters in the modern and the universe shortly after the Big Bang can be explained by the fact that the proportion of dark matter has decreased. We have now, for the first time, been able to calculate how much dark matter could have been lost, and what the corresponding size of the unstable component would be," says co-author Igor Tkachev of the Department of Experimental Physics at INR.

Astronomers first suspected that there was a large proportion of hidden mass in the universe back in the 1930s, when Fritz Zwicky discovered "peculiarities" in a cluster of galaxies in the constellation Coma Berenices—the galaxies moved as if they were under the effect of gravity from an unseen source. This hidden mass, which is only deduced from its gravitational effect, was given the name dark matter. According to data from the Planck space telescope, the proportion of dark matter in the universe is 26.8 percent; the rest is "ordinary" matter (4.9 percent) and dark energy (68.3 percent).

The nature of dark matter remains unknown. However, its properties could potentially help scientists to solve a problem that arose after studying observations from the Planck telescope. This device accurately measured the fluctuations in the temperature of the radiation—the "echo" of the Big Bang. By measuring these fluctuations, the researchers were able to calculate key cosmological parameters using observations of the universe in the recombination era—approximately 300,000 years after the Big Bang.

However, when researchers directly measured the speed of the expansion of galaxies in the modern universe, it turned out that some of these parameters varied significantly—namely the Hubble parameter, which describes the rate of expansion of the universe, and also the parameter associated with the number of galaxies in clusters. "This variance was significantly more than margins of error and systematic errors known to us. Therefore, we are either dealing with some kind of unknown error, or the composition of the ancient universe is considerably different to the modern universe," says Tkachev.

The concentration of the unstable component of dark matter F against the speed of expansion of non-gravitationally bound objects (proportional to the age of the Universe) when examining various combinations of Planck data for several different cosmological phenomena. Credit: MIPT

The discrepancy can be explained by the decaying dark matter (DDM) hypothesis, which states that in the early universe, there was more dark matter, but then part of it decayed.

"Let us imagine that dark matter consists of several components, as in (protons, electrons, neutrons, neutrinos, photons). And one component consists of with a rather long lifespan. In the era of the formation of hydrogen, hundreds of thousands of years after the Big Bang, they are still in the universe, but by now (billions of years later), they have disappeared, having decayed into neutrinos or hypothetical relativistic particles. In that case, the amount of dark matter in the era of hydrogen formation and today will be different," says lead author Dmitry Gorbunov, a professor at MIPT and staff member at INR.

The authors of the study analyzed Planck data and compared them with the DDM model and the standard ΛCDM (Lambda-cold dark matter) model with stable dark matter. The comparison showed that the DDM model is more consistent with the observational data. However, the researchers found that the effect of gravitational lensing (the distortion of cosmic microwave background radiation by a gravitational field) greatly limits the proportion of decaying dark matter in the DDM model.

Using data from observations of various cosmological effects, the researchers were able to give an estimate of the relative concentration of the decaying components of dark matter in the region of 2 percent to 5 percent.

"This means that in today's universe, there is 5 percent less dark matter than in the recombination era. We are not currently able to say how quickly this unstable part decayed; may still be disintegrating even now, although that would be a different and considerably more complex model," says Tkachev.

Explore further: 3 knowns and 3 unknowns about dark matter

More information: A. Chudaykin et al, Dark matter component decaying after recombination: Lensing constraints with Planck data, Physical Review D (2016). DOI: 10.1103/PhysRevD.94.023528

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RNP
5 / 5 (9) Dec 28, 2016
Open access copy of the paper here: https://arxiv.org...8121.pdf
cantdrive85
1.8 / 5 (16) Dec 28, 2016
"Let us imagine that dark matter consists....

Ahhh yes, the fanciful imaginings of the plasma ignoramuses pontificating about that which they are experts, unicorns, leprechauns, and other imaginary inventions conjured up by thought experiments to save their failed guesses and hide their obvious stupidity. Such is modern astrophysics...
Ultron
2.4 / 5 (14) Dec 28, 2016
In other words - scientists got the usual result when comparing mainstream Lambda-cold dark matter model to real observational data: It does not fit. Logical conclusion would be that the model is flawed, but mainstream physicists stubbornly refuse to search for real theory which would fit the observational data.
humy
4.4 / 5 (13) Dec 28, 2016
dark matter is currently by far the best explanation of the observations of how galaxies rotate. To just dismiss dark mater without bothering to providing an alternative explanation to these observations is completely unscientific and idiotic as it would leave a huge unsolved mystery of why the galaxies rotate in such a way as to apparently break the known laws of gravity; 'apparently' only if you reject the existence of dark matter.

There are other alternative theories to dark matter theory to those observations and those alternative theories should be tested where and when possible but they currently make far more unsupported assumptions than dark matter theory so, until if or when we have some good evidence to support one of these alternative theories, dark matter theory is the best we've got and should currently be considered the most likely explanation.
This is just the way good science works.
Bigbangcon
2.5 / 5 (13) Dec 28, 2016
In other words - scientists got the usual result when comparing mainstream Lambda-cold dark matter model to real observational data: It does not fit. Logical conclusion would be that the model is flawed, but mainstream physicists stubbornly refuse to search for real theory which would fit the observational data.


If properly followed, this "logical conclusion" would undo the mathematics driven "GR- Big Bang" theology and would demolish the virtual edifice that modern official cosmology so cleverly constructed and so fanatically protects!
cantdrive85
1.9 / 5 (15) Dec 28, 2016
dark matter is currently by far the best explanation of the observations of how galaxies rotate.

Not even close, Anthony Peratt's galaxy formation model;
http://www.plasma...ormation
has the flat rotation curve, not to mention numerous other characteristics that are observed.
To just dismiss dark mater without bothering to providing an alternative explanation to these observations is completely unscientific and idiotic ...galaxies rotate in such a way as to apparently break the known laws of gravity

To just grasp at fairy dust without understanding the matter (plasma) at hand is what is completely unscientific and idiotic. BTW, no "known" laws of gravity need be broken, just fixing the broken understanding of the plasma physics at hand by those who are charged with studying the matter. It's as simple as that, cast aside the psuedoscientific mumbo jumbo employed by astrophysicists in favor of real physics.
humy
3.8 / 5 (10) Dec 28, 2016
dark matter is currently by far the best explanation of the observations of how galaxies rotate.

Not even close, Anthony Peratt's galaxy formation model;...

irrelevant; what about the vast majority of galaxies with rotation that cannot apparently be explained without dark matter without violation of the law of gravity (if you reject dark matter) ? What is you explanation of that? You provide none.

To just dismiss dark mater without bothering to providing an alternative explanation to these observations is completely unscientific and idiotic ...galaxies rotate in such a way as to apparently break the known laws of gravity

To just grasp at fairy dust without understanding the matter (plasma) at hand is what is completely unscientific and idiotic.

What has "plasma" got to do with it? And I understand matter and plasma just fine as I have studied physics at university with good grades.
cantdrive85
2.2 / 5 (13) Dec 28, 2016
irrelevant; what about the vast majority of galaxies with rotation that cannot apparently be explained without dark matter without violation of the law of gravity (if you reject dark matter) ? What is you explanation of that? You provide none.

Please point me to this "vast majority" of galaxies to which you refer, you provided none. BTW, there is no "violation of laws of gravity", it's that gravity doesn't apply to this scale.
What has "plasma" got to do with it?

I need not say any more as plasma has everything to do with it. Given the proper physics, fairy dust is not needed.
http://www.plasma...sCLR.pdf
humy
3.9 / 5 (11) Dec 28, 2016
Given the proper physics, fairy dust is not

dark matter isn't "fairy dust."

Please point me to this "vast majority" of galaxies to which you refer,

simple; most galleries in the universe. This includs Andromeda, Black Eye Galaxy, Bode's Galaxy and most if not all in this list and that just a tiny few of them (obviously) ;
https://en.wikipe...galaxies

there is no "violation of laws of gravity",

thanks to dark matter, agreed.

it's that gravity doesn't apply to this scale.

which scale and why not i.e. Why wouldn't the law of gravity not apply under that 'scale'? It it beyond 10 light years or 100 or what and why? And how would gravity no longer apply beyond that arbitrary distance for no apparent reason whatsoever be less assumptive than dark matter theory? With dark matter, at least you don't have to assume a law of physics doesn't apply beyond a certain arbitrary scale!

Da Schneib
4.2 / 5 (5) Dec 28, 2016
Nice, thanks @RMP. We're finding out quite a lot from Planck.
IMP-9
4.3 / 5 (11) Dec 28, 2016
In other words - scientists got the usual result when comparing mainstream Lambda-cold dark matter model to real observational data: It does not fit.


No. There is tension between the CMB derived value of the Hubble Constant and the locally measured one. Tension, that means it's not statistically significant enough yet to rule anything out. Secondly when you have an issue like this it's only clear you don't understand something, it could be your cosmology is wrong or it could be a systematic of one of the datasets, you need to explore options and not jump to conclusions.
IMP-9
4 / 5 (12) Dec 28, 2016

Not even close, Anthony Peratt's galaxy formation model;
http://www.plasma...ormation
has the flat rotation curve, not to mention numerous other characteristics that are observed.


Ok. Can it match the galaxy clustering in SDSS? How does it explain the one and two halo clustering? Can it even do power law clustering at all?... This is the issue with a model which has never really developed, even if it get's rotation curves flat it's still 40 years behind current data which other models replicate. Dark matter doesn't just flatten rotation curves. Instead of pronouncing this model is correct maybe you electric universe people could put all that wasted energy into actual science for a change? Scary idea. There's a world of data out there waiting to be used.
Chris_Reeve
2.1 / 5 (11) Dec 28, 2016
Re: "To just dismiss dark mater without bothering to providing an alternative explanation to these observations is completely unscientific and idiotic as it would leave a huge unsolved mystery of why the galaxies rotate in such a way as to apparently break the known laws of gravity"

Just a reminder, folks:

Government researcher Anthony Peratt produced proper rotation curves in the EARLY 80s by simply modeling cosmic plasma as laboratory plasma. There's a distinction because in the laboratory, plasmas routinely conduct electrical currents -- whereas fluids-based cosmic plasma models essentially rule such behaviors out (no E-fields can sustain).

By all appearances, gravity is simply a short-range force. If more people were to simply calculate the gravitational force between our Sun and the nearest star, they would immediately realize this.
richk
5 / 5 (3) Dec 28, 2016
"the researchers found that the effect of gravitational lensing (the distortion of cosmic microwave background radiation by a gravitational field) greatly limits the proportion of decaying dark matter in the DDM model."

What does gravitational lensing have to do with the decay of the hypothetical decaying d.m. particle?

Read more at: http://phys.org/n...tml#jCp"
Da Schneib
4 / 5 (8) Dec 28, 2016
@richk, the article appears to be referring to this in the paper's introduction:

However, the second effect, the CMB distortion due to lensing by the large scale structures, was not considered in Ref. [1]. The difference in lensing power between the DDM and ΛCDM may be important since a part of the structure is decaying in the former model, and may be observable with high-quality data, such as Planck data.
What they're saying here is that there is bound to be gravitational lensing due simply to the DM, and if some of it decayed then that lensing should have varied over time as the decay progressed, and that this change in lensing should be observable in the CMB if the data is of high enough quality. Does that answer your question?

Good question, BTW.
jonesdave
3.5 / 5 (13) Dec 28, 2016
"Let us imagine that dark matter consists....

Ahhh yes, the fanciful imaginings of the plasma ignoramuses pontificating about that which they are experts, unicorns, leprechauns, and other imaginary inventions conjured up by thought experiments to save their failed guesses and hide their obvious stupidity. Such is modern astrophysics...


Oh yes, the imaginings of a f***wit who believes T & Ts rubbish. Laughable. Let's hear it cantthink. ...Oh yeah, brother, I belieeeeevvvveee. Oh yes, Wal, I believe.
Not gone well, has it? Electric comet? Not very electric, was it? Scott can't figure out a Z-pinch from a bleeding planetary nebula. Sh*t you guys are thick.
Anything else to add?
jonesdave
2.8 / 5 (11) Dec 28, 2016
@The idiot Reeve,
Just a reminder, folks:
Government researcher Anthony Peratt produced proper rotation curves in the EARLY 80s by simply modeling cosmic plasma as laboratory plasma. There's a distinction because in the laboratory, plasmas routinely conduct electrical currents -- whereas fluids-based cosmic plasma models essentially rule such behaviors out (no E-fields can sustain).

By all appearances, gravity is simply a short-range force. If more people were to simply calculate the gravitational force between our Sun and the nearest star, they would immediately realize this.


Hey, sh*t for brains, weren't you around for the bit where everybody ignored Peratt's nonsense? Because it didn't match observation? Or did that pass you by? Would you like me to remind you of the crap that idiots like Thornhill & Talbott & Scott have come out with over the years? Which has also failed to meet observation?
Bugger off, you idiot.
Merrit
4.3 / 5 (11) Dec 28, 2016
These electric universe people make me laugh. We all know gravity is by far the weakest force, but it doesn't depend on charge; just mass. The thing is the earth and many objects in the universe are relatively neutral in charge and thus the force of gravity is the dominant force.
MRBlizzard
4.2 / 5 (5) Dec 28, 2016
yep
1.7 / 5 (6) Dec 28, 2016
These electric universe people make me laugh. We all know gravity is by far the weakest force, but it doesn't depend on charge; just mass. The thing is the earth and many objects in the universe are relatively neutral in charge and thus the force of gravity is the dominant force.

The thing is...
http://ieeexplore...4316615/
arcmetal
1.8 / 5 (5) Dec 29, 2016
@Chris_Reeve
Government researcher Anthony Peratt produced proper rotation curves in the EARLY 80s by simply modeling cosmic plasma as laboratory plasma. There's a distinction because in the laboratory, plasmas routinely conduct electrical currents -- whereas fluids-based cosmic plasma models essentially rule such behaviors out (no E-fields can sustain).

By all appearances, gravity is simply a short-range force. If more people were to simply calculate the gravitational force between our Sun and the nearest star, they would immediately realize this.

I wonder how well this matches up with Verlinde's theories of entropic gravity. I think Halton Arp will have the last laugh.
cantdrive85
2.1 / 5 (7) Dec 29, 2016
Why am I not surprised jonesdumb proffers a crass childish response. Probably because he can see it all falling apart. Such as this article where they describe energy transfer in plasmas as a discharge mechanism, just as what has been proposed by the EU.

cantdrive85
2.6 / 5 (5) Dec 29, 2016
cantdrive85
3 / 5 (4) Dec 29, 2016
The thing is the earth and many objects in the universe are relatively neutral in charge and thus the force of gravity is the dominant force.

Not sure what "relatively neutral" means, last I checked it's either neutral or not. The presence of Earth's fair weather electric field and the measured voltage differential between the Earth and other points in the solar system only goes to reveal your ignorance or willingness obfuscate the truth.
IMP-9
4.5 / 5 (8) Dec 29, 2016
What does gravitational lensing have to do with the decay of the hypothetical decaying d.m. particle?


CMB lensing is sensitive to the matter distribution between the CMB surface of last scattering and the observer. The proposal they are testing is to slightly decrease the matter density over time so the matter density at recombination (which the CMB powerspectrum measures) is higher than the current density. This is to ease tension in the value of the Hubble Constant measured with the CMB and measured locally. CMB lensing probes the epochs in between those two as the lensing sensitivity (or kernel) peaks at about 1/3 the age of the universe. The lensing isn't sensitive to the decay of particles just to the change in the matter density over time.
nikola_milovic_378
1 / 5 (5) Dec 29, 2016
All those who believe that there was a big bang, the universe is expanding, there is dark matter and dark energy, and they represent the nature of the dark stain on the awareness and we can call it their "antisvjesnost".
The universe is a sphere of infinite radius, filled drug, ether, from which matter is formed and it returns to the state of ether. Here, there are certain processes of formation and disappearance of matter.
How can anyone believe in a story or theory that has no logical natural surface.
Science, to date, has not learned that arises and disappears matter how it occurs gravity, magnetism, electrical charge, heat is what is antimatter and the like. If that does not know how we can draw conclusions that depend on that knowledge?
Merrit
2.3 / 5 (3) Dec 29, 2016
Relatively neutral as in the charge to mass ratio is very small. Most of the positive and negative charges cancel out. Compared to a hypothetical oxygen atom with 2 extra electrons would have a much higher charge to Mass ratio and would be effected much more by e fields vs gravitational fields.
nikola_milovic_378
1 / 5 (6) Dec 29, 2016
Science, it seems, went to a dead-end knowledge and there is no way to correct and return to the right path, if it is not respected and studied the existence of the spiritual entity of the universe (SEU), This is an immense power to create and matter, and all of matter and energy.
Science has no knowledge of what energy is and what the subject matter and how they transform from one state to another (matter into energy and vice versa)
I'll help you:
 -materija are quarks, electrons and positrons
-Energy the "ether condensate in the formation of matter and to the gluon, which is obtained annihilation of electrons and positrons.
The basis of celestial bodies formed a community 3kg (three quarks and gluons), which when it receives a positron, proton occurs, and when an electron is formed antiproton.
When he entered the proton electron, neutron yields, as the same as if the 3kg enters gluon.
And so on!
cantdrive85
2 / 5 (4) Dec 29, 2016
Relatively neutral as in the charge to mass ratio is very small. Most of the positive and negative charges cancel out. Compared to a hypothetical oxygen atom with 2 extra electrons would have a much higher charge to Mass ratio and would be effected much more by e fields vs gravitational fields.

Even partially ionized matter (even slightly; i.e. far less than 1%) will be affected much more by EM fields vs gravitational fields, for much further distances. And charges don't "cancel out" anywhere in reality, only in your maths equations. In reality, there is an equalization process that involves energy transfer and the likely progenitor of most of the Universe's physical processes. It is important to remember maths is but a tool and equations shan't be reified to determine physical reality. It's the same trap with such pseudoscientific notions as magnetic reconnection where maths concepts are used to describe physical reality in an non-scientific manner.
Merrit
3.7 / 5 (3) Dec 29, 2016
E fields are responsible for a lot of phenomenon such as water surface tension due to one side of the water molecule being slightly positive and the other negative. But e fields have no effect on orbits or galaxy rotations.
Consider a negatively charged mass near the earth. It will pull on every proton and push on electron. If you were to calculate the net force for every single one you would come up with a result close to Zero. For gravity, however, every proton and every electron are pulling on the charged mass. Although small individually, when you add up everyone in the earth it sums to a significant force.
I hope this basic explanation helps
cantdrive85
2 / 5 (4) Dec 29, 2016
But e fields have no effect on orbits or galaxy rotations.

That's the presumption, but then 86% more fairy dust is required to make it work out. Then again, electric fields work out just fine;
https://medium.co...5q22y9f6

Peratt's models don't require DM, only models that ignore the real properties of plasmas need conjure fairy dust to explain reality. It's not science.
Kron
3.7 / 5 (3) Dec 29, 2016
@cantdrive85, What you think science is is not.
It's not science.

Physical sciences are about modelling the physical world. You have a prejudice towards a specific model (and while this is perfectly fine), your personal prejudice towards this model does not make it a more correct depiction of the physical world than a physical model you are prejudiced against. See how this works?

We can never know whether a specific model truly depicts reality. That is not the realm of science. Models just have to work. That is their only purpose. If sprinkling some fairy dust on a model fixes it to working level so be it. On the flip side to this,(see, it is not a one sided coin), a model accepted by the majority does not falsify other working models. You are free to use a model of your choosing. I still use Newtons models(while remaining aware of their limitations).

If you want to remove Dark Matter as a possibility you must prove it isn't there.
cantdrive85
1.7 / 5 (6) Dec 30, 2016
If you want to remove Dark Matter as a possibility you must prove it isn't there.

I don't have to do anything of the sort, besides, DM proponents have shown via an endless parade of observation and experiment that DM clearly does not exist. All that is necessary is providing a model that doesn't require fairy dust, Plasma Cosmology fits the bill.
Benni
1.5 / 5 (6) Dec 30, 2016
Consider a negatively charged mass near the earth. It will pull on every proton and push on electron. If you were to calculate the net force for every single one you would come up with a result close to Zero. For gravity, however, every proton and every electron are pulling on the charged mass. Although small individually, when you add up everyone in the earth it sums to a significant force


For sure GRAVITY won't distinguish it's attractive force as to the type of mass. Electric fields will function in accordance to the manner that gravity fields arrange concentrations of mass, density of mass takes over from there as to how conductive they become for the perpetuation of electric & magnetic fields.
Da Schneib
5 / 5 (2) Dec 30, 2016
@IMP-9,
The lensing isn't sensitive to the decay of particles just to the change in the matter density over time.
I have to point out here that if there is decay, then there will be a different rate of change than if there is not; thus the change in density over time *is* sensitive to the decay, and would constitute evidence to support it.

Meanwhile your point about the tension between the CMB power spectrum measurements of the density of dark matter and more recent measurements, for example the supernova data, is well taken. I left that out of my explanation for @richk and he should take note of it.
humy
5 / 5 (7) Dec 30, 2016
If you want to remove Dark Matter as a possibility you must prove it isn't there.

I don't have to do anything of the sort, besides, DM proponents have shown via an endless parade of observation and experiment that DM clearly does not exist..

this is simply not true.
WHICH observations and experiments prove that dark matter (DM) doesn't exist?
-give an example.
We currently have evidence for DM. We currently have no good evidence that there is no DM.
Benni
1 / 5 (5) Dec 30, 2016
DM proponents have shown via an endless parade of observation and experiment
..you're on the right track, but more specifically they resort to a catchphrase called INFERRED GRAVITY.

DM Enthusiasts are totally reliant on all sorts of INFERRED GRAVITY narratives upon which such inferred models, completely unknown to the laws of physics, rise or fall. These INFERRED GRAVITY models are the reason Einstein got into heads on battles with the likes of Zwicky back in the 1930's- 40's.

In GR, Einstein calculated PHOTON DEFLECTION (gravitational lensing) of a photon within 0.02% based upon the Visible Mass of the Sun. If there had been 80-95% Missing Matter anywhere near the vicinity of the Sun, Einstein's computation with such a degree of accuracy would have been impossible.

Einstein apprised Zwicky of the conundrum he created with his missing mass narrative, so Zwicky in turn did what he thought would be the smart thing & kept DM in envelopes outside the galaxy.

cantdrive85
1 / 5 (3) Dec 30, 2016
WHICH observations and experiments prove that dark matter (DM) doesn't exist?

All of them since the fairy dust cannot be found.
IMP-9
4.6 / 5 (9) Dec 30, 2016
Einstein apprised Zwicky of the conundrum he created with his missing mass narrative, so Zwicky in turn did what he thought would be the smart thing & kept DM in envelopes outside the galaxy.


Wow, you really don't have a problem with lying do you? Zwicky didn't come up with dark matter halos. Dark matter halos were only seriously considered the year before Zwicky died (Ostriker & Peebles etc), he wrote no papers on them. Secondly Einstein of course died nearly 20 years earlier, he certainly never discussed halos with Zwicky. Lastly the NFW profile which describes the density profile of a dark matter halo is peaked in the middle, not empty as you wrongly claim.

https://en.wikipe..._profile

Your history is even worse than it appears to as back in Zwicky's day he believed dark matter was neutron stars and other dense objects. He would never have looked for it in the Sun. Do think harder about your next fantastic story.
Benni
1 / 5 (6) Dec 30, 2016
Your history is even worse than it appears to as back in Zwicky's day he believed dark matter was neutron stars and other dense objects. He would never have looked for it in the Sun. Do think harder about your next fantastic story.
..........less "fantastic" than this ludicrous story you just concocted above. This is the problem with you people who live in the fantasyland of Cosmic Fairy Dust, along with all your Inferred Gravity narratives, you don't study the backgrounds of your icons.

It was Zwicky who postulated counter gravitational Envelopes of DM encompassing Spiral Galaxies to prevent the radial arms from imploding into the central hub of the galaxy.

It was Zwicky who coined the term "Spherical Bastards" in calling out Einstein for his synopsis of the Structure of the Universe in Gr. Yeah, because Einstein did not believe in an Infinite Universe, Zwicky went on a foul mouthed name calling binge on no less than Einstein, the same as you do here.

IMP-9
4.4 / 5 (8) Dec 30, 2016
I have to point out here that if there is decay, then there will be a different rate of change than if there is not


I was not claiming otherwise, I think you've misread my post. My point was in their model it doesn't matter if the dark matter decays or miraculously vanishes, they're not measuring any actual decay process.

tension between the CMB power spectrum measurements of the density of dark matter and more recent measurements


There is no tension in the dark matter density, the tension is with H_0. This tension is the whole point of this work and the paper it is based on.
IMP-9
4.5 / 5 (8) Dec 30, 2016
It was Zwicky who postulated counter gravitational Envelopes of DM encompassing Spiral Galaxies to prevent the radial arms from imploding into the central hub of the galaxy.


Prove it. Show us the paper where he did that. I've had enough of your self-contradictory stories, put up or shut up.
Benni
1 / 5 (6) Dec 30, 2016
It was Zwicky who postulated counter gravitational Envelopes of DM encompassing Spiral Galaxies to prevent the radial arms from imploding into the central hub of the galaxy.


Prove it. Show us the paper where he did that. I've had enough of your self-contradictory stories, put up or shut up.


Hey, neophyte......plug the topic into a search engine & find it for yourself, you're far too old to expect me to be your babysitter.
IMP-9
4.1 / 5 (9) Dec 30, 2016
It was Zwicky who postulated counter gravitational Envelopes of DM encompassing Spiral Galaxies to prevent the radial arms from imploding into the central hub of the galaxy.


Prove it. Show us the paper where he did that. I've had enough of your self-contradictory stories, put up or shut up.


Hey, IMP-9 you're completely right. I completely fabricated all these stories because I cannot win an argument on the basis of physics. I shouldn't demonise people who aren't even alive to defend themselves particularly when I cannot be bothered to even make up citations. I offer my most humble apologies and no matter how much I may deny or resent admitting the error of my ways the apology will be true. After all, you can google the so it definitely happened. Thank you IMP-9 for defending fact and reason. -- Regards, Benni


Don't mention it buddy. : )
Da Schneib
3.6 / 5 (5) Dec 30, 2016
I have to point out here that if there is decay, then there will be a different rate of change than if there is not
I was not claiming otherwise, I think you've misread my post.


The lensing isn't sensitive to the decay of particles just to the change in the matter density over time.
I don't think so. If you didn't mean that you shouldn't have said it.

My point was in their model it doesn't matter if the dark matter decays or miraculously vanishes, they're not measuring any actual decay process.
Then you should have said it's not *directly* sensitive to it.

tension between the CMB power spectrum measurements of the density of dark matter and more recent measurements
There is no tension in the dark matter density, the tension is with H_0.
Again, direct vs. indirect; H_0 is also dependent upon the density of DM.

What you didn't say is as significant as what you did.
Benni
1 / 5 (4) Dec 30, 2016
Hey, Benni, you're completely right. I completely fabricated all these stories because I cannot win an argument on the basis of physics. I shouldn't demonise people who aren't even alive to defend themselves particularly when I cannot be bothered to even make up citations about things never proven to exist. I offer my most humble apologies for my laziness and no matter how much I may deny or resent admitting the error of my ways the apology will be true. After all, you can google the so it definitely happened. Thank you Benni for defending fact and reason. -- Regards, Imp9


You're welcome Imp9, your apology is graciously accepted.

Benni
1 / 5 (4) Dec 30, 2016
What you didn't say is as significant as what you did.
.......and you have told us you have, or have seen, pics of Black Holes but have refused to share them with us. Could you kindly help Imp9 out a little bit here & set an example in creating links to subject matter that the rest of us are just too lazy to search for ourselves?

By the way, include a pic of the telescope through which the pic was made.
Merrit
2.5 / 5 (2) Dec 30, 2016
I believe the issue of DM arises from incomplete understanding of GR. For instance, it isn't possible for relatively to be asymmetrical. Our time dilation can't change simply because we compare ourselves to different objects like a spaceship approaching earth at relative velocities.
Also imagine two spaceships leave opposite galaxies on a head on collision both going 0.6C. The distance between them is decreasing at 1.2C. This only becomes a problem when one is considered stationery.
Now, take that light clock on a spaceship example. It works great until the guy on the ship tips his clock so the light moves parallel to motion. They will both still observe the same average speed for light, but you quickly realize it is impossible for both observers to see a constant speed for light both on the ship and the stationery observer outside the ship. For one to see light moving at a constant speed the other must see its speed differ from moving with or against the ships velocity.
arcmetal
5 / 5 (1) Dec 30, 2016
@kron
@cantdrive85, What you think science is is not.
It's not science.


If you want to remove Dark Matter as a possibility you must prove it isn't there.


And this is where I would stop debating this nonsense, since you can't prove a negative. Its called the "the devil's proof". The Devil's Proof states that you can have evidence to prove that something exists, but lack of evidence does not prove that something does not exist.

In essence DM is a unicorn. Unicorns exist because you can't provide me with proof that they don't exist.
Merrit
2.5 / 5 (2) Dec 30, 2016
Then there is gravitational time dilation. What is the actual mechanism? Is it the gravity well itself or just the apparent gravity? We have yet to do an experiment to test this. Gravity might well increase as we go deeper at first due to the density of the core. But, using a scale calibrated at sea level in combination with time dilation experiment at different depths like 1 mile intervals enough sensitivity should be able to determine which is causing time dilation.
Da Schneib
4.2 / 5 (5) Dec 30, 2016
Our time dilation can't change simply because we compare ourselves to different objects like a spaceship approaching earth at relative velocities.
Observers don't see their own time as dilated.

Also imagine two spaceships leave opposite galaxies on a head on collision both going 0.6C.
There's no problem here. Observers in the ships will see space and time such that the other ship will be approaching them at less than c.

It works great until the guy on the ship tips his clock so the light moves parallel to motion.
This also doesn't introduce any problems. Everyone in or on the ship or sharing its motion sees nothing peculiar; an observer who sees the ship as moving sees it compressed along the direction of motion. Work this out and you'll see that they all still see light moving at the speed of light.

[contd]
IMP-9
4.2 / 5 (5) Dec 30, 2016
If you didn't mean that you shouldn't have said it.


Again you're misreading it. What I meant was that the lensing was not sensitive to the actual process of particles decaying, only that there are fewer left over. I'm pretty sure that was clear from the context but I'll try to be more clear in future.

Da Schneib
4 / 5 (4) Dec 30, 2016
[contd]
The trouble you're having, @Merrit, is with frames of reference. You're confusing what various observers see with one another. You have to pick one observer, figure out everything they see, then pick another observer and work out everything *they* see. If those observers see one another in motion, then they will not see the same things. You can convert what one sees into what the other sees using a mathematical formula called a "coordinate transformation," or "transform" for short. Relativity specifies that transform, that's all.
Da Schneib
3.7 / 5 (3) Dec 30, 2016
If you didn't mean that you shouldn't have said it.


Again you're misreading it.
I can't misread what you didn't say. I understood it; I was pointing out that it's incomplete, since you didn't say that lensing isn't *directly* affected by the hypothetical process of particles decaying. What I was concerned about is that @richk understand it thoroughly.

And you did point out the tension is in the measurements, a very important point that I missed, so don't take it personally.
IMP-9
3.7 / 5 (6) Dec 30, 2016
Again, direct vs. indirect; H_0 is also dependent upon the density of DM.


No, I don't mind the bit of pedantism for the sake of clarity before but that statement is wrong. Tension in cosmology is what happens when two independent estimates of a parameter disagree outwith quantified errors. The tension this paper refers to is the tension in the Hubble Constant. In cosmology the Hubble Constant is determined by a lot of things including the dark matter density but that doesn't mean tension in H_0 implies tension elsewhere. Different parameters have different constraints and degeneracies with other parameters. The Riess et al. H_0 paper which kicked all this off doesn't even measure Omega_m. This proposal attempts to resolve the H_0 tension with a varying Omega_m*a^3, that doesn't mean based on current constraints that there is tension in Omega_m. Planck 15 Cosmological parameters shows there is no tension with low-z in the matter density.

Da Schneib
3.7 / 5 (3) Dec 30, 2016
Then there is gravitational time dilation. What is the actual mechanism?
Gravity warps spacetime. It does so in such a way that objects appear to behave like they are being acted upon by an attractive force, and objects that do not move within the field appear to be experiencing dilated time.

Is it the gravity well itself or just the apparent gravity?
You can't separate them that way.

We have yet to do an experiment to test this.
This is incorrect. We have to account both for SR and for GR when using GPS to get sub-meter positioning accuracy.

Gravity might well increase as we go deeper at first due to the density of the core.
No, actually it doesn't work like that; just the opposite. Gravity decreases as we go deeper below the surface. That's because instead of being acted upon only from below, we are also acted upon by the portion of the Earth above us.
[contd]
Da Schneib
4 / 5 (4) Dec 30, 2016
@IMP-9, I suppose I'm the victim of my own pedantry. BTW, looks like someone is trying to start a fight; please note that the 1-star ratings are some third party. You're getting 5s from me.

You're correct, I didn't note that DM density is one of many factors that combine to determine H_0.

However, all this pedantry has made me think of something: what is it precisely that the DM is supposed to have decayed into that *doesn't* affect H_0? You can't destroy mass, even if it's dark matter; you can only convert it into another form of energy. So the total lensing shouldn't be able to change. I think this hypothesis (decaying DM) is a little shaky based on that. I'd be very interested in your thoughts on how this works.
Benni
2 / 5 (4) Dec 30, 2016
Gravity might well increase as we go deeper at first due to the density of the core.
No, actually it doesn't work like that; just the opposite. Gravity decreases as we go deeper below the surface. That's because instead of being acted upon only from below, we are also acted upon by the portion of the Earth above us.


.........and Schneibo, you just finally learned something about the Inverse Square Law & why Black Holes can never exist, pleased to see you've been reading what I've been writing about for so long.

Now, just take a cue from what you've been learning from me regarding application of the ISL & apply it to the hypothesized structure of Black Holes & you'll finally come to a comprehension why such stellar masses of hypothesized infinite gravity & infinite density cannot exist.

Da Schneib
3.7 / 5 (3) Dec 30, 2016
[contd]
But, using a scale calibrated at sea level in combination with time dilation experiment at different depths like 1 mile intervals enough sensitivity should be able to determine which is causing time dilation.
We actually have more sensitive probes of gravitational effects than that. The most well-known is Eddington's experiment to show that starlight is bent around the Sun, which he performed during a total eclipse a few years after GR was published by Einstein. Another is the Hafele-Keating experiments, in which an atomic clock was flown in an aircraft and its synchronization loss compared to an identical clock with which it was pre-synchronized was measured after it was returned to the ground. These are only two among many- a score or more- of such experiments that confirm both types of time dilation.
Da Schneib
4 / 5 (3) Dec 30, 2016
Just as a reminder:
-m'' + m'n' - m'² - 2m'/r = 0
m'' + m'² - m'n' - 2m'/r = 0
e⁻²ⁿ (1 + m'r - n'r) - 1 = 0
R₂₂ sin² ϕ = 0

Source: http://www.etsu.e...esis.pdf
IMP-9
4.3 / 5 (6) Dec 30, 2016
You're getting 5s from me.


Same. They're nothing wrong with having a proper discussion.

what is it precisely that the DM is supposed to have decayed into that *doesn't* affect H_0?


It's a very good question, I haven't read the previous paper that put forward the model. I assumed the intention was that the particles would decay to radiation, which would still contribute to the evolution of H_0 but they would be diluted in energy density more quickly than matter as radiation is. (1+z) to the 4th instead of 3rd because redshift+3D dilution. I don't know how much cosmology you know but I can expand on that if necessary. Upon looking into it:

We assume that decay occurs into invisible massless particles and does not produce too many photons...


So I think the idea is similar but no observable background. The paper is not great at explaining and uses confusing and deeply annoying notation. I'll see if I can find more detail.
Merrit
2.5 / 5 (2) Dec 30, 2016
@Da I realize gravity would decrease as you go deeper if earth were a uniform density sphere. The issue is the center of the earth is very dense. Yes, earth above you pulls up, but if center is dense enough being closer to it could offset this. This is the purpose of the scale initialized at sea level. To measure change in force of gravity.
Merrit
2.5 / 5 (2) Dec 30, 2016
@Da in reference to the time clock on its side. In order for outside observer to see light traveling at C the light plus spaceship must be traveling at C. Or .5 for light and .5 for ship when traveling in same direction. And -1.5c for light and .5c for ship when traveling in opposite directions. This would lead to the person inside seeing light change speeds.
If person inside sees light traveling at constant speed, then the outside observer would have to see light going faster when light going towards front and slower when moving towards back. Having the length shortened due to speed has no effect on this whatsoever. It simply impossible for both too see constant speed.
Da Schneib
4.2 / 5 (5) Dec 30, 2016
They're nothing wrong with having a proper discussion.
:D

what is it precisely that the DM is supposed to have decayed into that *doesn't* affect H_0?
It's a very good question, I haven't read the previous paper that put forward the model.
Thanks. I like to think I ask good questions.

My immediate thought was that they were talking about lensing through known filaments; this would differ in character from lensing from, say, a gas of photons or neutrinos, and Planck's directional sensitivity would give data that could be used to check that. I'll be interested to see if that pans out when you're done with your research.

So I think the idea is similar but no observable background. The paper is not great at explaining and uses confusing and deeply annoying notation. I'll see if I can find more detail.
Please do. This should be a very interesting conversation.
Da Schneib
4 / 5 (4) Dec 30, 2016
@Da I realize gravity would decrease as you go deeper if earth were a uniform density sphere. The issue is the center of the earth is very dense.
Not so dense that going deeper wouldn't result in less total gravity field. The core is also fairly small compared with the mantle, so its total gravity even at higher density shouldn't be enough to cancel the entire effect of the shell theorem.

I really recommend taking a look at the experiments that have been done to confirm time dilation; Wikipedia has a pretty good article on it: https://en.wikipe...irmation

Be aware that SR time dilation is tested in every collision in every particle accelerator on an ongoing basis. So is relativistic mass gain. Physicists in fact count on them and would immediately spot any deviation.

BTW, please address me as "Schneib." "Da" is an article. ;)
Da Schneib
3.7 / 5 (3) Dec 30, 2016
@Da in reference to the time clock on its side. In order for outside observer to see light traveling at C the light plus spaceship must be traveling at C.
This is incorrect. Once the light leaves the source, it is no longer affected by the source or by the ship. It is freely moving in space, and the ship cannot move space. Everyone will see the light moving at c at all times (unless it enters a transparent medium within which the speed of light is not c- but if there's no glass, for example, between the observers on the ship, then this doesn't apply).
Benni
1 / 5 (3) Dec 30, 2016
I realize gravity would decrease as you go deeper if earth were a uniform density sphere. The issue is the center of the earth is very dense. Yes, earth above you pulls up, but if center is dense enough being closer to it could offset this.


Density of a given MASS has nothing to do with the strength of the field of gravity associated with it. Gravity of a given MASS is not DENSITY dependent, it is MASS dependent only. When the Inverse Square Law is applied to computation of any mass, gravity is always zero at the center, this is a TESTABLE Law of Physics.

There are tinfoil hat wizards of smart who show up in this chatroom claiming that infinite gravity can exist at the singularity of a Black Hole simply because they claim infinite density exists there, this is the classic fool's game of Perpetual Motion because they fail to perceive only finite compressive forces from the MASS above the center are what creates the density within the core, not gravity.
Merrit
4 / 5 (1) Dec 30, 2016
@schneib Actually, please reference preliminary reference earth model. You will see that due to the extreme density of the core, gravity doesn't start dropping off until you reach the inner core and that is the point gravity is the highest. They have a nice chart. So unfortunately, those gps location below sea level actually experience more gravity in addition to being in a deeper gravity well. I reviewed the experiments and they all assume it is gravity well and not apparent gravity. I did not see a single experiment specifically trying to determine which is the cause of GTD. I honestly cam see it going either way.
Da Schneib
4 / 5 (4) Dec 30, 2016
Lenni ignores the meaning of "surface" again, confusing it with "event horizon" again, after being pwnt for playing games with ratings and transparently stopping when it doesn't work.

Pitiful. And amusing.
Merrit
2.5 / 5 (2) Dec 30, 2016
@schneib in reference to the clock I mean if you could actually see the light bouncing back and forth inside the clock.
How about another example. If I am inside a spaceship traveling 0.9c how can light appear to be moving at C both from the rear and the front? Light should be approaching your ship around 0.1c from behind and coming at you at 1.9c from the front. Once it passes your window and enters your ship it would obviously be going C again, but that transition is what causes the blue and red shifts.
Benni
1 / 5 (3) Dec 30, 2016
Lenni ignores the meaning of "surface" again, confusing it with "event horizon" again, after being pwnt for playing games with ratings and transparently stopping when it doesn't work.

Pitiful. And amusing.


The usual petty & petulant Schneibo, still unable to explain the Inverse Square Law because you need to nullify it or you can't have your Black Hole fantasyland..
Da Schneib
4 / 5 (4) Dec 30, 2016
@schneib Actually, please reference preliminary reference earth model. You will see that due to the extreme density of the core, gravity doesn't start dropping off until you reach the inner core and that is the point gravity is the highest. They have a nice chart. So unfortunately, those gps location below sea level actually experience more gravity in addition to being in a deeper gravity well. I reviewed the experiments and they all assume it is gravity well and not apparent gravity. I did not see a single experiment specifically trying to determine which is the cause of GTD. I honestly cam see it going either way.
I'll need to see links to your references.

The density of liquid iron is about 7; the density of rock in the mantle about 5. Looking at the size of the core (about 15% of the Earth's volume) and the mantle (about 84% of the Earth's volume), it's obvious that what you claim cannot be correct. Simple math, 0.15 x 7 << 0.84 x 5 tells us that. The ratio is 1000:1.
Da Schneib
4 / 5 (4) Dec 30, 2016
@schneib in reference to the clock I mean if you could actually see the light bouncing back and forth inside the clock.
From what frame? If your frame is the ship, you see nothing unusual. If your frame is an outside observer who sees the ship as moving, then you have to account for time dilation and length contraction along the line of motion; you have to do the transforms. Do all the math and you'll see light moving at the speed of light all the time.
Merrit
5 / 5 (1) Dec 30, 2016
@schneib here is the earth link. https://en.m.wiki...th_model
Da Schneib
4 / 5 (4) Dec 30, 2016
How about another example. If I am inside a spaceship traveling 0.9c how can light appear to be moving at C both from the rear and the front?
Your example ignores relativistic time dilation and relativistic length contraction along the line of motion. These are not notional in any way; they have been measured by the experiments you denigrate. I would suggest you examine these experiments again, after discarding your prejudices based upon your personal experience.

I will repeat that a distinction between a "gravity well" and "apparent gravity" is meaningless as far as I can tell.

[contd]
IMP-9
4.3 / 5 (6) Dec 30, 2016
Please do. This should be a very interesting conversation.


So after doing a bit of digging I think my initial reaction was essentially correct. If their model is very much like one of the reviews they cite then they are modeling in the contribution of the decay radiation to cosmology. The dominant effect seems to be that it falls more quickly in energy density over time more quickly than matter would and so at late times the contribution to the lensing is damped (because there is a lower energy density than no decay). They also appear to track the effect on structure growth of this radiation field. I can't be sure because niether they, nor the main paper they cite, specify their equations. Maybe it's not quite as simple as deleting the matter as I previously suggested but I suspect the effect of considering the decay radiation is negligible.
Da Schneib
4.2 / 5 (5) Dec 30, 2016
[contd]
Light should be approaching your ship around 0.1c from behind and coming at you at 1.9c from the front.
"Should be" according to your common experience which does not generally include the capability to observe the propagation of light as other than instantaneous. In fact, all observations of light by any observer in any state of motion observe light moving at the speed of light. This conundrum is the heart of Special Relativity.

Thanks for the link; I'll review it now.
IMP-9
4.4 / 5 (7) Dec 30, 2016
My immediate thought was that they were talking about lensing through known filaments; this would differ in character from lensing from, say, a gas of photons or neutrinos, and Planck's directional sensitivity would give data that could be used to check that. I'll be interested to see if that pans out when you're done with your research.


They may be considering the effect of the decay radiation on the lensing, I can't be sure because they don't specify. As you can imagine the radiation would disperse and decrease the lensing amplitude in addition to the effect of dilution I described above.

The observation they're looking at specifically is the Planck lensing powerspectrum. The nice thing about CMB lensing is it covers all redshifts so a subtle change over time can be probed. Because there is different amounts of structure at different times and it's at different distances you get structure imprinted on the powerspectrum at slightly different scales.
Merrit
1 / 5 (1) Dec 30, 2016
@schneib I am glad you asked about apparent vs gravity well. It is very important for cosmology and DM. Please review link about rotation curves of our milky way galaxy https://en.m.wiki...Way).JPG
The red is expected and blue is observed. Gravitational time dilation being based on apparent gravity vs gravity well could explain our galaxy rotation. Apparent gravity would increase as we approach the bulk of our inner universe, then it would begin to drop off until we approached the black hole in the middle. This would increase our apparent gravity again. So Yea it only matters for explaining all DM away. So like you said no big deal. Not even worth an experiment.
IMP-9
4.4 / 5 (7) Dec 30, 2016
They just basically have a model for the powerspectrum and are fitting it to the data and trying to ease the H_0 tension simultaneously.

It's an interesting paper and a cute idea. My main thoughts about this work is that it's interesting but their model has 2 additional degrees of freedom and this is motivated by a 2.5 sigma tension, it's not justified yet. They also don't do any proper Bayesian or AIC test of this additional freedom, I don't think their chi squared tests cut it these days. It wouldn't hurt for these people to be a bit more verbose also, I sympathies with your earlier criticism.

I am however interested in the wider topic as these decaying dark matter models make other predictions such as an increased effect of large scale structure imprinting itself on the CMB, the late-time Integrated Sachs-Wolfe effect which is of interest to me.
Da Schneib
3.7 / 5 (3) Dec 31, 2016
One little detail, @Merrit: the PREM model doesn't show the crust, and the crust is all we have access to.
Da Schneib
4.3 / 5 (6) Dec 31, 2016
@IMP-9, I think ISW effect is what I was thinking about. And I think one of the free parameters you're talking about is matter concentration at early times. It could be very difficult to disentangle non-integrated and early time integrated SW effect from late-time ISW effect. This is because althrough we have pretty good galaxy maps for late times, I think, we still have a lot to learn about early times. Almost any early galaxy we see is unusually bright; this is obvious if you think about it. Any really rigorous analysis of SW effect in the CMB requires a thorough matter map as far back to the SLS as we can get, so we can cross-correlate to the matter density.

At a significance of 2.5 sigma or so, I sense your unease with making a hypothesis to explain something that could easily just be instrumental error. Added to my question about the decay path DM is supposed to follow, I think this paper is, as you say, "cute," but the data to test it are going to take a long time to get.
Benni
1 / 5 (3) Dec 31, 2016
Added to my question about the decay path DM is supposed to follow, I think this paper is, as you say, "cute," but the data to test it are going to take a long time to get.


......that's for sure, first they need to find the stuff before they can even test it. Everytime a more advanced DM detection device is set up, the prospects for finding the stuff becomes even more dim.

How anyone with credibility in Nuclear Physics can even bring up the subject "about the decay path DM is supposed to follow" when a Spectroscopy for it has never produced, is someone with a novice state of mind dabbling around in a Perpetual Motion land of fantasy.

Zwicky looks at the Coma cluster of huge Elliptical Galaxies & imagines he sees them moving at what he considers unimaginable velocities, so he gravitationally INFERS that the rest of the 99.9999999999% of the Universe functions in the same manner even though he has no red or blue shifting spectroscopy to support the concept.
IMP-9
5 / 5 (5) Dec 31, 2016
It could be very difficult to disentangle non-integrated and early time integrated SW effect from late-time ISW effect. This is because althrough we have pretty good galaxy maps for late times, I think, we still have a lot to learn about early times.


As you say you can break this degeneracy with the cross-correlation with galaxy surveys. With the normal LCDM ISW effect the effect occurs only in accelerating cosmologies so low-z structures have the largest effect and the effect should disappear at about redshift~1. This does mean we can get away with shallow surveys as more distant galaxies essentially show no ISW effect. There is a second order effect which can occur in non-accelerating cosmologies but it's very small. If these decaying dark matter models are true then there may be an ISW like effect at higher redshift, that's an interesting prospect. As you say that's hard today but with Euclid it may be testable.
Da Schneib
5 / 5 (2) Dec 31, 2016
The picture I have of early ΛCDM is that DM doesn't come out of the BB clumpy, but concentrates into filaments after a while, and drags matter to it; I don't really have a clear timeline for that. You probably do. So what's the timing of that like? Is it all before the surface of last scattering, or mostly after it?
RNP
5 / 5 (4) Dec 31, 2016
@Da Schneib
The picture I have of early ΛCDM is that DM doesn't come out of the BB clumpy, but concentrates into filaments after a while, and drags matter to it; I don't really have a clear timeline for that. You probably do. So what's the timing of that like? Is it all before the surface of last scattering, or mostly after it?


As far as I understand ΛCDM, the DM content mapped the baryonic content very closely immediately after the big bang. It is only after primordial density fluctuations (e.g. as detected in the CMB) started the phase of contraction under gravity that the dissipative interactions of baryonic matter started to cause its distribution to differ significantly from that of non-dissipative dark matter (e.g. Baryon Oscillations). DM clustering therefore at least *started* to occur at a similar epoch to that of the baryonic material. This is most definitely after the surface of last scattering.
Da Schneib
5 / 5 (2) Dec 31, 2016
Looks like the CMB is currently thought to have been emitted by recombination, which places it before the Dark Ages. Thus, we can expect that as DM and baryonic matter condensed into filaments during the Dark Ages, some sort of inverse ISW effect would be evident: photons would enter an area where condensation was occurring, and exit it when it was more condensed, or enter an area that mass was being drawn away from into the filaments, and exit it when it was more rarefied. It seems to me that given the timeline for the Dark Ages, which is on the order of tens to hundreds of millions of years, certainly less than a billion, compared with the timeline for ISW effect, which is billions of years, we should be able to see the CMB fluctuations from that. On the other hand, it would also be dependent upon the density differences, which might not be as great as at later times.

Source: https://en.wikipe...universe

Have I understood the issues correctly?
Mimath224
5 / 5 (3) Dec 31, 2016
@Da Schneib etc. Before my comment would like to say that I am enjoying the conversation you and others are having and I don't have anything to add to it...a spectator? But I do have a problem which perhaps you/RNP/lMP might be able to help. Like to start with an analogy. I have a Head, Torso, Arms and Legs, 4 'pieces' that are me. I am a unit, a Human. But detach those 4 pieces am I still Human? (don't want to get into philosophical arguments here) Likewise for say a alligator(croc). My point is that all these units are different and result in very different 'detachments' so at the Universe epoch when the 4 forces were combined/unified etc. would that actually determine what existed in the aftermath, that is similar to my analogy? And was the type of original entity immaterial, the result having to be the forces that we know of. (continued)
Mimath224
5 / 5 (3) Dec 31, 2016
(continued) Or was the original entity in possession of 'choices' which could result in different forces (QM?) and did the entity have a constraining field keeping 'it' whole...could that field be DM so that at the beginning epoch of the universe DM becomes 'distributed'...rather like an inert 'skin'. On second thoughts, such ideas would mean a central 'core' and a hell of lot of DM around it. Nonsensical? Just a layman's thought, Ha!
Da Schneib
5 / 5 (3) Dec 31, 2016
Hey @Mimath, I have to tell you I'm listening to Shine On You Crazy Diamond, reading the history of Venice, watching Ohio State and Clemson, and cooking corned beef and cabbage, just at the moment. I might try to give you some response before the New Year, but don't hold your breath. ;)

Remember when you were young
You shown like the Sun
Shine on you crazy diamond
Now there's a look in your eyes
Like black holes in the sky
Shine on you crazy diamond

You were caught in the crossfire
Of childhood and stardom
Blown on the steel breeze
Come on you target for faraway laughter
Come on you stranger
You legend
You martyr
and Shine!
IMP-9
5 / 5 (3) Dec 31, 2016
into filaments during the Dark Ages, some sort of inverse ISW effect


The ISW effect however doesn't occur in non-accelerating cosmologies, so during matter domination it won't have occurred. The Rees-Sciama effect is the second (and higher) order version of the ISW effect does occur in non-accelerating cosmologies but it's very small, an order of magnitude smaller than the ISW effect at least. The ISW effect is currently detected at 3 sigma at best and that likely won't rise too much higher because the primary CMB anisotropies are so much larger. I think 7-9 sigma is the highest it could theoretically be measured with cross-correlation in standard LCDM, The RS effect therefore will likely never be measured. Some novel new test could be developed but I wouldn't hold my breath.

The dark ages will leave an imprint on the CMB however. The 21 cm line should be in absorption at some epochs which people are trying to detect.
Mimath224
not rated yet Dec 31, 2016
@Da Schneib, okay but while you're juggling all of that save a bit for me...on the other side of the world (new year came and went) I had sweet and sour pork with lots of pineapple.
Gosh, I'm older than that more of a 'dark globe' in the bush looking for Dark Matter, Ha!
Da Schneib
3.7 / 5 (3) Jan 01, 2017
Ah, I think I was talking about early time ISW effect. Of course with no way to detect the matter distribution at early times, because of the intervening Dark Ages, there'd be no way to distinguish its effects from the original anisotropies that are from before recombination.

Thanks for clearing that up for me, @IMP-9.
Mimath224
not rated yet Jan 01, 2017
@Da Schneib/RNP/lMP I'd like to thank you guys on the ISW topic. I've always had a problem understanding how it (and the NISW) works, or at least theoretically. Reading your discussion I obviously need to study...I particularly don't grasp scattering between surfaces etc. For example with regard to the present discussion as I understood it if the universe was matter controlled then objects like clusters & voids wouldn't evolve where the reverse is true if basically mostly under the influence of cosmic radiation (is DE classified in this?). So one of my problems would be is that if the universe contains much DM then the former should be true. But then I don't know if this internal or external cluster shape evolution. Surely the existence of one or other would indicate a 'measurable' quantity of DM or the lack of.
My mixture here shows my confusion...not to mention incorrect terminology...help?
richk
5 / 5 (2) Jan 03, 2017
@richk, the article appears to be referring to this in the paper's introduction:

However, the second effect, the CMB distortion due to lensing by the large scale structures, was not considered in Ref. [1]. The difference in lensing power between the DDM and ΛCDM may be important since a part of the structure is decaying in the former model, and may be observable with high-quality data, such as Planck data.
What they're saying here is that there is bound to be gravitational lensing due simply to the DM, and if some of it decayed then that lensing should have varied over time as the decay progressed, and that this change in lensing should be observable in the CMB if the data is of high enough quality. Does that answer your question?

Good question, BTW.

thanks. good answer btw
nikola_milovic_378
1 / 5 (1) Jan 05, 2017
It is easy to prove that all the stories about the existence of dark matter, dark energy, the Big Bang, the expansion of the universe, indeed, a mirage, a hollow story, nonsense and Sisyphean task.
If science has learned and knows what he created and what created both matter and energy, then only weird people can speculate about something invisible and fully current. Where are these people were born and when they formed, so are now at a very low level of awareness, a consciousness of the power of knowledge and the true causes of the phenomenon in the universe and in us.
nikola_milovic_378
1 / 5 (1) Jan 05, 2017
Everything in the universe is formed from the ether that fills infinite universe.
Matter consists of quarks, electrons and positrons, and energy gluons. The material and energy entity of the universe there is nothing else besides their many forms and different characteristics.
Gluons are energy in the form of "liquid state" when the gluon ether and evaporated to form an electron and a positron. The basic particles of matter is 3kg (three quarks and gluons three) when it enters the positron, proton occurs or when entering gluon, resulting neutron and so on until it reaches the celestial bodies.
All you have to go back to where respect the existence of the spiritual entity of the universe (SEU), which represents an immense power to create. This is the Creator of everything in the universe, not your stupid thought that it was a big bang, as the largest contamination of consciousness.

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