A Did the LUX Dark Matter Experiment Fail to Detect Dark Matter?

[rootone]

Is there any theory which posits the DM could be assemblages of different particles into units, just as regular atoms are?
Then though I guess the LUX experiment might have produced a result of that was the case.

 

[Orodruin]

The problem is, if they are so similar, then one should decay into the other unless they have exactly identical masses (at which point I'd wonder whether we should consider them different particles at all).

... or have no or a very supressed coupling to particles with masses smaller than the mass gap. It is not difficult to imagine such a scenario. The free neutron decays to a proton only because the electron (plus neutrino) are lighter than the proton-neutron mass gap. If the electron would have been much heavier (well, not that much) neutrons would not decay.

Is there any theory which posits the DM could be assemblages of different particles into units, just as regular atoms are?

Yes, but more like protons and neutrons are made from quarks. The words you are searching for are "composite dark matter".

 

[rootone]

The words you are searching for are "composite dark matter".

Thanks for that, it lead me to this:
http://arxiv.org/pdf/1512.01081v1.pdf
Which as a non-professional I found it to be comprehensible enough.
So dark analogs of atoms are candidates, but they would be very massive compared with ordinary matter.
The main problem though seems to be that in order for such a thing to form, we could expect abundances of isotopes in normal matter to be different to what they actually are.
A bonus though!. this theory apparently requires no rethinking of currently accepted physics.
It does require though, a single strange particle which is described in the paper as O−−

 

[Orodruin]

Thanks for that, it lead me to this:
http://arxiv.org/pdf/1512.01081v1.pdf
Which as a non-professional I found it to be comprehensible enough.
So dark analogs of atoms are candidates, but they would be very massive compared with ordinary matter.
The main problem though seems to be that in order for such a thing to form, we could expect abundances of isotopes in normal matter to be different to what they actually are.
A bonus though!. this theory apparently requires no rethinking of currently accepted physics.
It does require though, a single strange particle which is described in the paper as O−−

Be very careful of taking one arXiv paper as representative. There are other forms of composite dark matter that that paper does not cover.

 

[Traruh Synred]

QM will of course modify GR when and if we ever figure out how to make them consistent with each other. String/Brane theory claims to do this, but so far not in a very useful way. It conceivable that GR+QM will explain why the cosmological constant is so small, yet not zero, or may be not!
Q

 

[ProfChuck]

An important question regarding the properties of dark matter is "Does DM introduce Faraday rotation to signals that pass through it?". While by definition DM is not directly observable as a luminous source it may introduce artifacts to signals originating from more distant objects. These artifacts could include time dispersion and birefringence. A measure of such phenomena in the region of suspected DM has been suggested by Susan Gardner of the University of Kentucky.

(https://www.researchgate.net/publication/23417584_Shedding_Light_on_Dark_Matter_A_Faraday_Rotation_Experiment_to_Limit_a_Dark_Magnetic_Moment )

The results of these observations could shed considerable "light" on the dark matter question. Most importantly is DM exotic matter or is it just ordinary matter that is too cold to be detected directly by conventional astronomical methods and instruments.

 

[jerromyjon]

Your comment seems to be about dark energy (acceleration of expansion)

Yes. I was asking if the analogy makes sense: "dark energy is to expansion as dark matter is to mass"?

 

[Vanadium 50]

Most importantly is DM exotic matter or is it just ordinary matter that is too cold to be detected directly by conventional astronomical methods and instruments.

It is not ordinary matter.

• It is too transparent. This much ordinary matter would be visible as gas or dust.
• Big-bang nucleosynthesis limits the amount of matter to be atomic to ~10% of the total matter
• CMBR limits are similar
• Microlensing shows no clumping of the sort you would expect from atomic matter
• The Bullet Cluster shows a component of matter that interacts much less strongly than ordinary atomic matter

 

[jerromyjon]

The main problem though seems to be that in order for such a thing to form, we could expect abundances of isotopes in normal matter to be different to what they actually are.

My "guess" is that depends where you look, take the center of the milky way for example... we need a more "dynamic" inventory.

 

[RUTA]

We believe DM and DE are both manifestations of small geometric perturbations from idealized GR solutions. Here is a quick overview of our idea https://arxiv.org/abs/1605.09229 which will appear in IJMPD as an Honorable Mention in this year's GRF essay contest. We have redone the DM fits in this paper using the exact same fitting technique we used for DE (as shown in this paper), i.e., the fitting function uses explicitly the metric perturbation h_{\alpha \beta}. That will appear in a longer paper which will include a fit of the Planck CMB power anisotropy data (also using the same fitting technique). The bottom line in our approach is that mass is not an intrinsic property of matter, it is a relational property and can have different values in different contexts. This is already true in GR, e.g., an FRW dust ball interior to a Schwarzschild vacuum where M of the Schwarzschild metric is equal to, less than, or greater than the FRW proper mass depending on the FRW spatial geometry. So the matter of the FRW dust ball has two different values of mass, depending on the context.

 

[PeterDonis]

an FRW dust ball interior to a Schwarzschild vacuum where M of the Schwarzschild metric is equal to, less than, or greater than the FRW proper mass depending on the FRW spatial geometry.

How is the "FRW proper mass" defined? (I see a brief statement that might be relevant in the paper you linked to, but it doesn't give any details; it just gives two references, one of which is Wald's textbook, but with no chapter/page. A more specific reference to the chapter/page in Wald where this is discussed would be helpful.)

 

[RUTA]

How is the "FRW proper mass" defined? (I see a brief statement that might be relevant in the paper you linked to, but it doesn't give any details; it just gives two references, one of which is Wald's textbook, but with no chapter/page. A more specific reference to the chapter/page in Wald where this is discussed would be helpful.)

Proper mass is simply the mass obtained by integrating the dust density in the FRW ball, i.e., cosmology proper mass measured by the comoving observers of a dust-filled universe. The "dynamic mass" would be the mass obtained by observers outside the ball using M of the Schwarzschild geometry. I just ck'd and the arXiv paper has p. 126 for the Wald reference. The AJP paper is too old for the arXiv, but I can send a copy when I get to the office tomorrow if you'd like.

 

[PeterDonis]

Proper mass is simply the mass obtained by integrating the dust density in the FRW ball, i.e., cosmology proper mass measured by the comoving observers of a dust-filled universe.

Integrating with what measure?

 

[RUTA]

Integrating with what measure?

The FRW metric interior to the ball. Here is a link to the paper:
http://users.etown.edu/s/STUCKEYM/AJP1994.pdf

 

[phinds]

Yes. I was asking if the analogy makes sense: "dark energy is to expansion as dark matter is to mass"?

I doubt that question even makes sense. Would it even have occurred to you to ask it if what we call dark energy were called vacuum energy and dark matter was called Zwicky matter. The only thing they really have in common is our use of the word dark in their names.

 

[PeterDonis]

Here is a link to the paper

Thanks! I'll take a look.

 

[jerromyjon]

The only thing they really have in common is our use of the word dark in their names.

And that they are both undetectable in local space as normal matter and energy, they are more similar to each other than to anything else in physics. That could certainly be a coincidence but it could also be a connection. I'm not just going to flip a coin and see which way it lands, I'm keeping an open mind. =D

 

[mfb]

Electron neutrinos and muon neutrinos are much more similar than dark matter and dark energy.

I would argue that even neutral gas is more similar to dark matter than dark energy is.

 

[Vanadium 50]

dark matter was called Zwicky matter.

Please. Zwicky-Rubin matter.

 

[phinds]

Please. Zwicky-Rubin matter.

My point was simply "not 'dark' matter"

 

[jerromyjon]

I would argue that even neutral gas is more similar to dark matter than dark energy is.

Yes, I agree with you from a physics viewpoint.

My point was simply "not 'dark' matter"

Ignore the names of the phenomena and could you at least see that I have a sensible question at the heart of it all. Dark matter makes the stars in galaxies and clusters move differently than general relativity would predict. Dark energy makes all stars in galaxies and clusters (which are further apart and not bound) accelerate away from each other (at a lessening rate). They seem like 2 sides of the same galactic "coin" to me.

I do have a tendency to over-simplify things but there is a method to my madness and I do understand the finer implications of the details, even if I don't possesses the skills to quantify my thoughts, yet.

 

[PeterDonis]

Dark matter makes the stars in galaxies and clusters move differently than general relativity would predict.

No, dark matter makes the stars in galaxies and clusters move differently than they would move if the dark matter were not there. But the motion including the effect of the dark matter is perfectly consistent with GR, and the effect of dark matter, gravitationally, is the same as the effect of ordinary matter.

 

[mfb]

Stuff in galaxies and clusters would also move differently if regular matter would not be there. Even worse: we would not even have stars moving around.

 

[phinds]

Yes, I agree with you from a physics viewpoint.
And what other point of view would you like to bring to bear on the question?

Ignore the names of the phenomena and could you at least see that I have a sensible question at the heart of it all.

I disagree. Others have already pointed out the reasons.

 

[jerromyjon]

No, dark matter makes the stars in galaxies and clusters move differently than they would move if the dark matter were not there. But the motion including the effect of the dark matter is perfectly consistent with GR, and the effect of dark matter, gravitationally, is the same as the effect of ordinary matter.

So there is just random stuff we can't see, mixed randomly with the stuff we can see. Alright then. Thanks.

 

[Drakkith]

So there is just random stuff we can't see, mixed randomly with the stuff we can see. Alright then. Thanks.

Not quite random, no. It seems to be concentrated into roughly spherical "halos" around most galaxies and into other areas where a non-interacting type of matter would be expected to concentrate at. Offset from the point of collision between galaxies, for example, since the normal matter slows down during the collision but the dark matter passes right through and continues on.

 

[Laurie K]

Not quite random, no. It seems to be concentrated into roughly spherical "halos" around most galaxies and into other areas where a non-interacting type of matter would be expected to concentrate at. Offset from the point of collision between galaxies, for example, since the normal matter slows down during the collision but the dark matter passes right through and continues on.

We also get total rotational matter = dark matter + visible matter = visible matter x 2 \pi +/- 3%.

This 2 \pi is just the difference between the calculated rest mass, attributed to our astronomical observations and the sum (relativistic) mass, used in our Lambda CDM calculations which gives us dark matter.

 

[phinds]

We also get total rotational matter = dark matter + visible matter = visible matter x 2 \pi +/- 3%.

This 2 \pi is just the difference between the calculated rest mass, attributed to our astronomical observations and the sum (relativistic) mass, used in our Lambda CDM calculations which gives us dark matter.

Huh? "Relativistic mass" as related to dark matter? Clearly one of us is misunderstanding something. And what does pi have to do with dark matter?

 

[mfb]

We also get total rotational matter = dark matter + visible matter = visible matter x 2 \pi +/- 3%.

This 2 \pi is just the difference between the calculated rest mass, attributed to our astronomical observations and the sum (relativistic) mass, used in our Lambda CDM calculations which gives us dark matter.

The fraction of visible matter relative to total matter varies between galaxies by much more than 3%, such an equation does not make sense. The overall dark matter density is not known more precisely than 4%, so that doesn't work either.

The concept of relativistic mass is not used any more, but the difference between this and the visible mass is negligible (about 1 part in a million difference).

To summarize, your post doesn't make sense at all.

 

[Laurie K]

The fraction of visible matter relative to total matter varies between galaxies by much more than 3%, such an equation does not make sense.

In a universal sum calculation, like the percentages of dark matter and visible matter given by Planck 2013 data, it does make sense. In the Planck 2015 revision the total percentages included dark energy but the ratio shown between dark matter% and visible matter% remain the same.