# World's most sensitive dark matter detector set up

Discussion in 'Physics & Math' started by arauca, Jul 15, 2012.

1. ### araucaBannedBanned

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Is the dark matter in our solar system ?
Do we have dark matter on our earth ?
If the dark matter causes a lensing effect on galaxy
What effect cause it in the earth ?>

3. ### rpennerFully WiredStaff Member

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There is no factual support for this assertion. In post #5, AlphaNumeric clearly explains that dark matter does not interact much according to observation other than with gravity. This leaves open that it might interact via the weak force -- like neutrinos which only interact via the weak force and gravity. But AlphaNumeric also clearly explains that he thought he was told that neutrinos have been discarded as the main constituent of dark matter. The reason why is because they are too light and therefore don't clump as required by cosmological models.

<snark> Exactly -- As with Relativity and Cantor's diagonal proof, AlphaNumeric comes to the discussion armed with empirical knowledge based on detailed observation, sound logic, rigorous and time-tested theorems and above average intelligence and he has the gall to assert on this basis that he knows something. And then, mark you well, he tries to teach. Imagine if everyone with a Ph.D. in a field did the same -- where would it end?! </snark>
Correct again. AlphaNumeric is not the one bringing the dishonest discussion.
But children don't understand dark matter. They think "dark" means black when it actually means "not visible / transparent." Likewise children have nothing meaningful to say about the details of nucleosynthesis or cosmology. At best even a smart child is forced to use stupid analogies to fill in the gaps of their knowledge.
Yes -- it was obvious that AlphaNumeric was well-informed on a wide variety of physics and math topics and willing to share the fruits of his studies.

No one knows what dark matter is. It is a topic of ongoing research. In the context of this thread it is hoped by researchers that dark matter has a large WIMP component, because WIMPs are the only type of dark matter candidate their detector is sensitive to. WIMPs may or may not correspond to supersymmetric partners of standard model particles -- that would be a matter for research if WIMPs are detected or if supersymmetric grand unified theories develop enough to make testable predictions in cosmology.

If dark matter is WIMPs then you can never collect it because no material walls would impede it. It would be like trying to box up a sample of helium when all you have for the container is chicken wire mesh.

Current evidence strongly supports the hypothesis that most galaxies (including ours) have higher-than-average dark matter densities. A recent study of local stars showed evidence that there is about as much local intragalactic dark matter as predicted by the best models.
http://arxiv.org/abs/0907.0018
http://arxiv.org/abs/1205.4033

Yes. Every empirical reason to suspect this is true -- no empirical reason to suspect this is not true.
Yes. Every empirical reason to suspect this is true -- no empirical reason to suspect this is not true.
This question is based on two misunderstandings. Firstly, dark matter in volumes of cubic kiloparsecs bends light -- not galaxies. At the galactic level it mostly has a slight effect on stellar dynamics only easily seen in the statistical effects on large numbers of stars. Secondly, since the density is so low that the dark matter filling the whole Earth masses only about 0.6 kilogram. That's not enough to affect anything via gravity to the limit of experimental precision. Ask Google what 0.3 GeV/cm^3 times the volume of the Earth is.

5. ### chingluValued Senior Member

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Is massless gravity stimulation consistent with GR?

7. ### rpennerFully WiredStaff Member

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That was not well-written.

I shall answer assuming you meant "Is the assertion that massless phenomena are associated with a source of gravitation consistent with General Relativity."

Yes, because the Einstein curvature tensor $G_{ab} \equiv R_{ab} - \frac{1}{2} g_{ab} R$ is proportional to the stress–energy tensor $T_{ab}$ which has terms for momentum density, so that massless phenomena with momentum density like electromagnetic waves are associated with non-zero curvature.

8. ### AlphaNumericFully ionizedModerator

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Having massless particles in a field theory does not cause a problem for general relativity. The mass given by the Higgs mechanism is not the same as gravitational mass. I've already explained this. Are you bothering to read what people say? This is your usual tactic of asking what you think are questions which lead to some conclusion you think proves something in the mainstream wrong. It never does but that doesn't stop you doing it. Thus far in this thread all your questions have done is show you don't know basic physics, you don't bother to find out what the Higgs mechanism involves before dismissing it and you're willing to ignore people you quote. Multiple times.

If you have some point to make then make it. If not please crawl back under whatever rock you reside beneath and let people who actually want to learn and understand things talk in peace.

9. ### chingluValued Senior Member

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OK, this is correct.

Now, what massless particle is sufficient to stimulate gravity according the stress energy tensor that is sufficient that explain the 70-90% of the gravity stimulation in the universe that is not explained by mass.

We must remember, this particle does not couple with the electro-weak force, nor the strong nuclear force.

We have already demonstrated this particle must be massless because it would cause at least cause electron instability because of its mass.

Therefore, we must be able to supply parameters to the stress energy tensor that are sufficient to describe dark matter.

May I please see these parameters?

10. ### rpennerFully WiredStaff Member

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You make nonsensical assumptions in the process of asking a question and as a result, I lack confidence that you are working from empirical facts. Why do you say massless when the evidence points to about 23% of the missing mass as cold dark matter which by definition is fairly massive as particles go? You have made no argument as to why it should be massless and ignored my calculations. The remaining approximately 70% is called dark energy but corresponds closest to the "lamdba" term in Einstein's equation at the heart of general relativity.

Why do you say it cannot interact via the weak force? I expect to see a calculation based on empirical observations or a scientific citation.

11. ### RealityCheckBannedBanned

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Hi chinglu.

I have bolded and underlined that part of your post which I want to ask you about.

Can you explain what that electron instability would be that you allude to? By what mechanism would the instability be manifest between such 'massed' particles and the electron as you put it?

Thanks.

.

12. ### AlphaNumericFully ionizedModerator

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You're confusing dark matter with dark energy. It's simple mistakes like this which illustrate how your initial post, with its "Oh this is obviously nonsense!" attitude, was very misguided. You're showing you haven't done even the most rudimentary of reading up on the topic and instead just jumped to conclusions.

Particles which make up dark matter can couple to the weak force. Whether dark energy has a particle origin or is something else is currently unknown. In quantum field theory a field can contribute a vacuum energy so it could just be the accumulation of vacuum energy from particle fields we already know about (and some we have yet to discover), so it wouldn't need it's own particle. There are tentative ideas about dark energy and cosmological expansion, particularly inflation, which would view the effect of accelerating expansion to be related to a particle, known as an inflaton (not the lack of an 'i'). In string theory these can arise as quantisations of moduli fields describing the deformations in the topological structure of compact dimensions. The inflation controls the dynamics of the length parameter a(t) in the FRW metric, initially rolling down a potential such as to initiate inflation, before stabilising about a minimum, which leads to slower growth.

No, that is not a unavoidable implication. I'm not even aware of anyone making such an implication. In the case of the moduli fields I mentioned the excitations need not be massless and in general they are not due to being expressed in terms of fluxes attached to branes wrapped around the particular topological non-triviality the inflaton relates to. That's for dark energy, while in dark matter models, such as the MSSM (Minimally Supersymmetric Standard Model), the electron can be stable despite all the supersymmetric particles responsible for dark matter being much more massive, typically above 1TeV (about 8 times more massive than the newly discovered particle by the LHC).

Given you're obviously not even familiar with qualitative concepts pertaining to this stuff and you've shown a poor grasp of what makes things 'solid' I doubt that you would understand it if someone talked about the specifics of say an inflaton model or the MSSM. I suspect you're trying to do as you always do, which is ask someone else for proof of something then make inaccurate complaints about it.

There's plenty of freely available lecture notes on the MSSM. Go find one using Google, read it and then come back if you're unsure about something. I doubt such a procedure will lead to fruitful discussion but hope springs eternal.....

13. ### chingluValued Senior Member

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You have a problem with this logic. Non-massless dark matter will attack electrons and render them unstable.

Demonstrate your "cold" dark matter will not interact with electrons and cause instability that we do not see in experiments.

14. ### AlexGLike nailing Jello to a treeValued Senior Member

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This is total nonsense.

15. ### AlphaNumericFully ionizedModerator

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Please justify this statement. There is no mainstream model of dark matter which involves electron instabilities. There have been GUT models which allow for proton decays much faster than observed but not electrons. Electrons are stable in things like the MSSM or the EMSSM.

The MSSM does not have unstable electrons. That's an example of a model which contradicts your claims. Provide reasoning, clear and detailed, that any cold dark matter model necessarily leads to an unstable electron, including why this apples to the MSSM.

Oh and since I probably shouldn't assume you know what MSSM means, it stands for Minimally Supersymmetric Standard Model.

/edit later that day....

This morning, while thinking about this, I couldn't think of any viable model of particle physics which has the electron being unstable. The motivation for calling into question even the very concept is decays typically split things down into their constituents (ala proton decay), along with a possible transmuting of a piece, or they convert a particle into it's lighter relative (ala muon to electron decay). Decays stop and the particle becomes stable when the sequence of decays reaches the lightest particle consistent with whatever symmetries are involved. In the case of the electron you have electromagnetic charge conservation so the electron would have to decay in something with electromagnetic charge. But it is the lightest electromagnetically charged particle, even allowing for quark masses (about 1MeV compared to the electron's 0.5MeV, ignoring strong force effects). But since I'm not infallible and various exotic particle models are always being proposed and falsified I asked someone I work with who happens to have a PhD in supersymmetric dark matter physics and he had the same thoughts, namely what would the electron decay into? Models of cold dark matter, such as various incarnations of supersymmetric extensions of the Standard Model, have the electron as being stable even in the precense of dark matter particles (typically the lightest supersymmetric particle). Supersymmetry allows certain types of decays to occur which wouldn't otherwise occur in the Standard Model but the instability of the electron is not one of them in any one put forth so far.

As such chinglu's claim is falsified, in the sense that he asserts it is an inevitability for any model to have an unstable electron if it includes cold dark matter. This is not so in the case of the MSSM so chinglu is mistaken. Of course this doesn't mean it's impossible to construct a dark matter model which does make the electron unstable but the instability would have to be extremely weak as we have experimental data which shows the typical life time of an electron is at least something like $10^{39}$ years. This is because we'd done experiments looking for proton decays to test some GUT models like ones with an SU(5) gauge group (as this is the simplest one which contains the Standard Model group $SU(3) \times SU(2) \times U(1)$) and no detection of decays implying electron instability (since it is measured in the same way) were made. Thus even if chinglu can provide a model which allows the electron to be unstable in the presence of dark matter his assertion such thing is a necessity is false.

Last edited: Aug 3, 2012
16. ### chingluValued Senior Member

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We start with simple logic. Dark mater has mass or it does not.
If it does not, it needs to write equations for the energy stress tensor sufficient to implement the gravity stimulation necessary to implement the 70+% dark matter observed in the universe. Note, I am refuting RPenner's assertions on the dark matter compositions.

Now, can you write said equations or no.

Next, since these equations are not possible, we must assume dark matter has mass.

If it has mass, then any reasonable person would conclude if is occupies 70% of gravity, then it certainly exceeds the mass of an electron.

That proves if dark matter is true, it would disrupt the electron which is a contradiction, because the electron is stable.

Last your worthless belief in MSSM asserts the following,
"The only unambiguous way to claim discovery of supersymmetry is to produce superparticles in the laboratory. Because superparticles are expected to be 100 to 1000 times heavier than the proton"
http://en.wikipedia.org/wiki/Minimal_Supersymmetric_Standard_Model

Show me anything in nature as a particle that produces these masses for particles.

Otherwise, my argument holds true.

17. ### rpennerFully WiredStaff Member

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Chinglu has twice demonstrated that he cannot even read wikipedia articles on cosmology, let alone have a meaningful fact-based reasonable discussion.

Here Chinglu is twice corrected on the difference between "Dark Matter" (暗物质 roughly "dark/concealed/secret substance") and "Dark Energy" (暗能量 roughly "dark/concealed/secret energy"). Confusing these two is unacceptable.
And then, after twice being corrected, Chinglu makes the same mistake again.
Both dark matter and dark energy are primarily inferred from their gravitational effects. That's where $\Omega_{\tiny c} \approx 0.226$ comes from in papers like this http://lambda.gsfc.nasa.gov/product/map/dr4/pub_papers/sevenyear/cosmology/wmap_7yr_cosmology.pdf

Incorrect -- all matter, including dark matter, has mass. If it didn't have mass, we wouldn't call it dark matter.
In papers like the above we get $\Omega_{\tiny c} \approx 0.226$ and $\Omega_{\tiny \Lambda} \approx 0.728$ which is where my claims that dark matter makes up about 23% of the universe and dark energy about 73% of the universe come from. My numbers have a basis in reality. You cannot simply assert facts without a basis in reality and still expect to call what you do "science." -- Like an authoritarian cult leader you have resorted to simply making up stories in an attempt to cement your authority on a subject on which you know nothing.

Actually, as the one making the unsupported claim about the makeup of the universe, all the burden of proof remains on you. Denial of the burden of proof at a minimum should be grounds to move this thread to Pseudoscience or The Cesspool. But since Alphanumeric and I never asserted dark matter was massless and since Alphanumeric and I never confused the percentage of dark matter with a number as high as 70%, it is ridiculous for you to demand that we support a position we never advocated.

It is ridiculous to claim that equations are not possible. The equations are trivial and in every GR textbook for a "dust"-filled universe. "Dust" is a technical term for a continuous perfect massive fluid that has zero pressure. The equations of motion and the demanded "equations for the energy stress tensor" are everywhere, but are irrelevant. Similarly the equations for a massless perfect fluid are in most books with a modified pressure term.
It is more correct to say observation of reality leads us to conclude that there is hidden mass in the universe, and we call this hidden mass "dark matter." Further, observation leads us to presume that the majority of the "dark matter" moved with non-relativistic velocities long before the first year since the big bang.

Incorrect. Any reasonable amateur would defer to the opinion of experts and any reasonable expert would conclude dark matter results in about 23% of the gravitational dynamics of the universe. Further, since "warm dark matter" with a per-particle mass of about $250 \, \textrm{GeV}/c^{\tiny 2}$ would have a relativistic velocity profile falling to non-relativistic speeds about 1 year after the big bang, detailed studies reject that this is adequately clumpy for our universe and therefore the actual "cold dark matter" must have a per-particle mass in excess of this example.

This is an example of a claim you made without facts or calculation. Therefore, the onus is on you to demonstrate this claim before continuing to make more claims. Electrons are unlikely to decay in any future model of physics simply because no lighter electrically charged particle is known. If you mean atoms should be ionized due to tidal disruption of very heavy particles, calculations earlier in this thread already excluded that as a possibility for dark matter candidates from 1-100,000,000,000,000 TeV.

The MSSM was listed as just one example of a physical theory that allows for both dark matter candidates and stable electrons. One does not have to "believe in" a physical theory to examine its conclusions.
The Z boson is about 97 times the mass of the proton. The Higgs boson candidate is about 130 times the mass of the proton. The top quark masses about 180 times the mass proton.

But you have never argued for any of your claims. You have evaded the burden of proof you created for yourself when you made original claims.

18. ### AlphaNumericFully ionizedModerator

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You have once again conflated dark matter and dark energy. This shows you are not reading what people say and you haven't done any reading on the subject, as it's a mistake you really shouldn't be making. This serves to illustrate much of your 'conclusions' are undermined by a lack of evidence or lack of sufficient checking.

Considering what you're requesting isn't anything to do with dark matter people haven't considered such equations. That doesn't mean they are impossible.

You haven't shown the equations are not possible and the reason for concluding dark matter has mass is different from your 'reasoning' (and I use that in it's vaguest sense).

Again, you're making conclusions based on flawed reasoning. Besides, initially it was suggested dark matter could be due to neutrinos and their masses are much much less than electrons. The fact the contribution to the universe's total mass is more than normal matter doesn't mean the particles are necessarily massive, just very numerous. After photons the most numerous particles in the universe are neutrinos.

This is an assertion you have now repeated and have been asked to justify. There are particle physics models of dark matter and all of them have a stable electron. Thus it is not logically impossible to have dark matter made of massive particles and an electron be stable.

As Rpenner has said, the W bosons are about 80 times a proton mass, the Z boson is 90 times the proton mass, the newly discovered particle at CERN is 125 times a proton mass and the top quark is about 140 times the proton mass. The existence of such particles does nothing to imply the instability of the electron. In fact the existence of the W and Z bosons is what leads to things like other particles decaying into the electron which, as I mentioned in a previous post, is the lightest charged particle and thus likely to be stable.

You have no argument. You've shown you're willing to ignore things people say, you haven't done any reading on the subject as you keep conflating dark energy and dark matter, you haven't justified anything, just repeated assertions, you just dismiss things which illustrate your assertions to be false and you illustrate how little you know about particle physics when you wonder about particles 100 times the mass of a proton when there's been HUGE media coverage of a particle that massive being found at CERN!

I'm going to ask you one last time before I consider your posts little more than trolling..... please provide any model of particle physics which has an unstable electron when massive (100+ GeV) particles are involved. Please demonstrate the logical impossibility of such things as the MSSM, which have massive particles and a stable electron. If you fail to show you have grasped there's a difference between dark matter and dark energy then I'll conclude you aren't really bothering to look anything up, you're just making assertions without due consideration. If you want to do that go to the pseudoscience forum, such posts aren't for this forum. If I have to enforce that I will.

19. ### chingluValued Senior Member

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You and I seem to be not communicating.

My posts have centered around gravity stimulation.

For every gram of glowing material we can detect, there may be tens of grams of dark matter out there.

http://www.lbl.gov/Science-Articles/Archive/sabl/2006/Jan/Rubin-Dark-Matter.pdf

Now, you claimed dark matter is able to stimulate gravity through the stress energy tensor.

I want to see your proof with the equations in order to prove the total amount of gravity stimulation in the universe.

Can you do this yes or no?

Once you do this, I want to see that your dark matter candidate does not make the electron unstable since it has mass.

Can you do this yes or no?

20. ### chingluValued Senior Member

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As Rpenner has said, the W bosons are about 80 times a proton mass, the Z boson is 90 times the proton mass, the newly discovered particle at CERN is 125 times a proton mass and the top quark is about 140 times the proton mass. The existence of such particles does nothing to imply the instability of the electron. In fact the existence of the W and Z bosons is what leads to things like other particles decaying into the electron which, as I mentioned in a previous post, is the lightest charged particle and thus likely to be stable.

If this is even true, this does not have any effect on the dark matter particle(s).

These particle roam freely whereas bosons are constituent particles.

You are comparing apples and oranges.

If these dark matter particle(s) are free to roam, then they will interact with electrons. Otherwise, prove free neutrons will not interact with electrons.

21. ### AlphaNumericFully ionizedModerator

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Yes, and the problem is your end since you don't seem to be reading our posts.

You keep demanding either things no one has said or things you can easily find out yourself. Look on www.arxiv.org for papers on dark matter and supersymmetry. You demand people provide a dark matter model with a stable electron, I say to look at the MSSM and you just ignore it. You have been given the information you need to answer your question. If you're unwilling to go read books or articles and demand everyone types out everything here for you then you're trolling.

Now you're just making random excuses. You've been told to look at the MSSM, which provides stable electrons and candidates for dark matter. This responds to the question you asks. If you're too lazy, stupid or dishonest to look up such information then no one can help you because you're incapable of learning. Put some effort in and stop trolling with your nonsense.

22. ### chingluValued Senior Member

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You folks are wondering in fields of the illogical.

The entire issue here is what is the nature of dark matter if it is viable.

First, I suggested that dark matter must have mass. AN claimed that is false.

Then, I challenged AN to provide gravity stimulation that is equal to the dark mass with mass itself. The reason? Any mass running around the universe at the dark mass concentration would render the electron unstable because it would interact with the electron with its mass which is obviously not seen in nature.

AN and RPenner claimed the stress energy tensor can describe the gravity stimulation. Yet, dark matter does not interact with the weak nor strong nuclear forces. So, there is no stress energy tensor. Since energy it not emergent under the rules of physics, their argument completely fails.

That is where we are in this debate.

So, you 2 need to up the game a bit.

23. ### rpennerFully WiredStaff Member

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This is a damn lie. Here is where you falsely claimed that either dark matter is not local or has no mass and are corrected.

So as you see, it is Chinglu, not anyone else who proposed the ridiculous notion that dark matter had no mass, when its mass density is what is measured.

That is a lie. If dark matter has only mass and no interactions, it could have a mass a million times as large as a proton and never be detected via interaction with electrons. Likewise if dark matter has only mass and weak interactions, then it could have roughly the penetrating power of neutrino and almost never interact with electrons. The claim that the electron would be rendered unstable is not a prediction of any identified physical postulates or calculations and where physical models have been identified those physical models predict that the electron is always stable.

This is a lie. No one has demonstrated that dark matter does not interact with the weak force.
This is a lie. The stress energy tensor is just that of a field of a pressureless ideal fluid as previously stated.

I think it's time to for the moderators to appeal to the admins for chinglu's final disposition. We rate him