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Which alternative do you think is the most likely to solve the Dark Matter problem?
Chronos said:Agreed, Garth, but that aside, would you agree some amount of 'dark matter' is necessary?
Agree on this.Garth said:The Higgs boson ... will do nothing to resolve the identity of DM.
Ouch, forgott the IMBH alternative in the poll...I voted 'other' as I maintain that DM does exist but that originally it was mainly baryonic in form, that an initial 'IGM' of Omegab ~ 0.22 formed Pop III stars which themselves left IMBHs some gas and dust. This gas and dust then formed the visible matter in the galaxies as we know them, and the IMBH's form the DM.
Being made of dark matter myself, I find it indespensible.Chronos said:Agreed, Garth, but that aside, would you agree some amount of 'dark matter' is necessary?
I would not claim that there is nothing left to discover in terms of exotic particles, axions or whatever. I'm just wary of using such to resolve the 'galactic rotation curve', 'cosmological missing mass' and 'large structure formation' problems of GR and thereby conclude that a 96% majority of the universe's mass inventory consists of totally unknown forms of DM and DE.Chronos said:Agreed, Garth, but that aside, would you agree some amount of 'dark matter' is necessary?
How does GR square up with QT and the ZPE, a 10140 mismatch?Mike2 said:Could the zero point energy of quantum fields be modified by gravity? Might this explain the extra mass around galaxies and clusters, etc? Could this be the dark matter we are looking for?
Has it been proven that not any kind of distribution of normal, baryoinic matter could account for DM effects because normal matter would scatter light too much, whereas DM WIMPs would not?Chronos said:Microlensing is the most punishing evidence in favor of DM. I was hardcore against the DM model when it first came out, but, microlensing [and to a certain extent large scale structure studies] convinced me that DM is the only logical explanation.
Einstein was on this track as he continued to develop his theory of General Relativity. By 1920, he was convinced that GR needed a dynamical ether to mediate gravitation and inertia. He also accepted the need for an EM ether to allow for the propagation of light through space, but did not see that the two were united. By 1924, as shown in his paper "On the Ether" he viewed the gravitational and EM ethers as one and the same and was working toward modifying GR to encompass them.Mike2 said:Could the ZPE of QFT have enough energy/mass to produce the same effects as DM. Maybe with very large volumes of space there might be enough energy to bend light and change galatic rotation curves.
To this end, is the ZPE background independent? Or does the energy produced depend on the curvature of the spacetime in which it is calculated?
And on magnetic fields:Einstein "On the Ether" said:The general theory of relativity removes a defect of classical dynamics: in the latter, inertia and weight appear as totally different manifestations, quite independent of one another, in spite of the fact that they are determined by the some body-constant, i.e. the mass. The theory of relativity overcomes this deficiency by determining the dynamical behaviour of the electrically neutral mass-point by means of the geodesic line, in which inertia and weight effects can no longer be distinguished. Thereby it attributes to the ether, varying from point to point, the metric and dynamical properties of the points of matter, which in their turn are determined by physical factors, to wit the distribution of mass or energy respectively. The ether of the general theory of relativity differs from that of classical mechanics or the special theory of relativity respectively, in so far as it is not 'absolute', but is determined in its locally variable properties by ponderable matter. ... The fact that the general theory of relativity has no preferred space-time coordinates which stand in a determinate relation to the metric is more a characteristic of the mathematical form of the theory than of its physical content. ... The metric tensor which determines both gravitational and inertial phenomena on the one hand, and the tensor of the electromagnetic field on the other, still appear as fundamentally different expressions of the state of the ether; but their logical independence is probably more to be attributed to the imperfection of our theoretical edifice than to a complex structure of reality itself.
Einstein was striving for simplification and unity. A polarizable, self-interacting quantum vacuum field would very neatly serve as his GR ether, with no need for additional entities.Einstein "On the Ether" said:The Earth and sun have magnetic fields, the orientation and sense of which stand in approximate relationship to the axes of rotation of these heavenly bodies. ... It rather looks as if cyclic movements of neutral masses are producing magnetic fields. The Maxwell theory, neither in its original form, nor as extended by the general theory of relativity, does not allow us to anticipate field generation of this kind. It would appear here that nature is pointing to a fundamental process which is not yet theoretically understood.
SpaceTiger said:Dark matter is one of those things that sounds dubious to everyone when they first hear it. I can assure you, however that those of us in the field are by and large convinced of it. I can't tell you what it is, but I can say what it most probably isn't:
1) Neutrinos - We have a limit on the mass and can calculate their approximate abundance. They appear to contribute negligibly.
2) More careful GR - Standard GR is very well understood and I find it extremely implausible that we would have just overlooked something in modelling the systems.
3) MOND - Although not completely dead, the theory is on its last legs. It can't seem to reproduce the CMB power spectrum or large scale structure and there is still no real theoretical motivation for the "modification" of gravity.
4) Errors in the Data - Dark matter is a many, many-sigma statistical result at this point. There's absolutely no way to do away with it with more careful observations.
5) MACHOs - The microlensing observations in the Milky Way halo and the low value of [itex]\Omega_b[/itex] pretty much rule this out. Primordial black holes are also a possibility, but are also almost ruled out.
EL said:I totally agree with you SpaceTiger. I can see you have answered "other". Is this because you have some special other candidate in mind, or that you just don't believe in any of the listed candidates, or simply just because you are being "scientific" and reject to answer a question you don't know the answer to?
SpaceTiger said:Mostly the latter. My intuition tells me only that the dark matter is probably a particle of some kind. Beyond that, I don't feel qualified to say anything about exactly which particle it's most likely to be.
Would that be an interacting or non-interacting DM particle?Chronos said:The DM particle most likely is very massive Probably on the order of 10 Tev - right around the Higgs mass.
EL said:What about if I force you to pick one kind of particle, what would your answer be then?
Why do you think it should be massive?Chronos said:The DM particle most likely is very massive Probably on the order of 10 Tev - right around the Higgs mass.
SpaceTiger said:Neutralinos are popular amongst the experts, so I'll go with that.
I have been considering this for quite a while, and am still of the opinion that this is correct as long as it can be shown that the field is quite equal in all places with no (unexplained) concentrations of the effect.Turbot said:Einstein was striving for simplification and unity. A polarizable, self-interacting quantum vacuum field would very neatly serve as his GR ether, with no need for additional entities.
Probably yes, with the equipment and accuracy available. But, even if it was today, I believe that the "entity" they were trying to detect would leave a null result. Someone posted earlier (above) a mention of the "frame dragging" experiment which was done on a very basic level until the satellite (GRACE) was up, plus some more recent satellite laser-ranging measurements.Turbot said:Were the early "null' detections of the ether (via ether drift interferometry) actually null?
cscott said:Saw this on Slashdot this morning: http://science.slashdot.org/science/05/10/10/1052224.shtml?tid=160&tid=14
Oh, I'd love if there'd be only one (main) solution.Nereid said:I'd just love there to be more than one 'solution'!
I agree with you here (And I'd like to change my vote to other). The Unruh effect is a vacuum energy/zero point energy effect that I am presently working on. No conclusions yet. It might be that the virtual particles created by the ZPE/CC/vacuum energy might exist long enough to create a gravitational field of its own. So there might be an average force produced by virtual pair. Anyone ever study this? How long must a particle exist before it produces a gravitational field?X-43D said:IMO, vacuum energy (whatever it is) is the only explanation for the apparent missing mass problem. Perhaps the CMBR has something to do with this.
Dark matter is a type of matter that makes up about 85% of the total matter in the universe. It does not emit or absorb light, making it invisible to telescopes and other instruments. Its presence is inferred through its gravitational effects on visible matter.
Nucleonic forces are the forces that hold together the particles that make up an atom, such as protons and neutrons. These forces are mediated by particles called gluons and are responsible for the stability of atoms and the formation of chemical bonds.
Recent research has suggested that dark matter may interact with nucleonic forces, specifically through a weak force known as the weak nuclear force. This interaction could potentially explain some of the observed properties of dark matter.
By studying the potential interaction between dark matter and nucleonic forces, scientists hope to gain a better understanding of the nature of dark matter. This could help explain its origin, composition, and behavior, and ultimately lead to a more complete understanding of the universe.
Scientists are using a variety of methods, such as particle accelerators and astronomical observations, to study the potential interaction between dark matter and nucleonic forces. They are also developing new theoretical models to better understand this relationship and its implications for our understanding of dark matter.