Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Favorite DM particle

  1. Sep 30, 2004 #1

    wolram

    User Avatar
    Gold Member

    http://arxiv.org/pdf/astro-ph/0403064
    This is a 2004 paper 34 pages on dark matter, various candidates for
    DM are discussed and categorised
    anyone have a favorite DM particle?.
     
  2. jcsd
  3. Sep 30, 2004 #2

    Garth

    User Avatar
    Science Advisor
    Gold Member

    Thank you for the link to Gondolo’s paper, we have quite a choice as to our favourite particle. I quote from it:

    He continues,
    He concludes:
    Quite

    But consider; in Gondolo’s paper Figure 1 on page 2 is the well-known concordance Omega m v Omega lambda diagram. The total Omega is thought to be unity because the WMAP data favours a flat universe; this constrains Omega lambda as the total is thought therefore to be unity.

    However other models are also conformally flat, such as SCC which is so - even with a total Omega of only one third. If you notice putting Omega m = 0.33, and therefore the equivalent Omega lambda = 0.66, fits quite well too, in fact it is dead centre of the intersection of the CMB and distant supernovae data sets.

    Furthermore the Omega baryonic matter in SCC is 0.22, (effective Omega lambda still 0.66), which is the centre of the Galaxy red shift survey data set.

    So one way of understanding the different data sets plotted on that diagram is to say the CMB and distant supernovae data indicate cosmological dynamics determined by the total density whereas the galaxy survey data indicate the dynamics of galaxies and clusters within the universe determined by the baryonic matter, dark and luminous, within those clusters.

    Just food for thought.

    My favourite dark matter particle is the proton, closely followed by the electron and neutron!

    Garth
     
    Last edited: Sep 30, 2004
  4. Sep 30, 2004 #3

    selfAdjoint

    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Garth, conformally flat is different from flat!
     
  5. Sep 30, 2004 #4

    Garth

    User Avatar
    Science Advisor
    Gold Member

    True, but conformal transformations preserve angles. The CMB data is based on the angular size of anisotropies in the radiation. The conclusions drawn carry through to conformal transformations of the particular GR model.
    Garth
     
  6. Sep 30, 2004 #5
    I vote for the axion, a WIMP whose mass must be in the range 10-6-10-3 eV. The axion is in the category of cold dark matter. I used to have preference for hot dark matter (exemple, the neutrino), but WMAP result indicates that the missing matter is most likely cold dark matter
    There's a theory that proposes that the axion could act as dark energy as well. Is called Axion Phantom energy
    http://arxiv.org/abs/hep-th/0401082
     
    Last edited: Sep 30, 2004
  7. Oct 1, 2004 #6

    wolram

    User Avatar
    Gold Member

    http://www.astro.umd.edu/~ssm/mond/
    Garth, Meteor, do you have a view on how these particles arrange
    themselves with galaxies?
    The url is a link to the mond pages, as you know an alternative to DM.
    Although i do not subscribe to the theory it is a good one stop reference.
     
  8. Oct 1, 2004 #7

    Garth

    User Avatar
    Science Advisor
    Gold Member

    MOND would be more persuasive if the mechanism that produces the anomalous acceleration was known.

    SCC predicts the density of the universe is 2/3 baryonic and 1/3 false vacuum energy. Models already run on such a constitution in the past (2/3 CDM, 1/3 HDM) modelled galaxy formation quite nicely
    Garth
     
  9. Oct 1, 2004 #8
    Wolram,
    dark matter is postulated to exist throughout all the universe, not only in galaxies, but also in the intergalactic medium. In disk galaxies for example, they exist in the disk but also in a spherical volume around the disk called the halo. The most widely accepted model for dark matter in halos is the famous NFW profile (Navarro, Frenk, White, 1996). It seems that the ratio of dark matter to visible matter varies according what scale of the universe are you examining. See

    http://hermes.physics.ox.ac.uk/users/Astrophysics/guides/galaxies/dkmatter.shtml [Broken]

    "Within galaxies the amount of dark matter appears to exceed the amount of visible matter by a factor of 10 to 1 in some cases, and even more than this for a few galaxies. Within galaxy clusters the ratio of dark to visible matter appears to be even larger still and a general result is that the ratio of dark to visible matter appears to increase as one observes on larger scales. On the very largest scales of all (the scale of the observable Universe) visible matter may account for less than 1% of all the matter in the Universe."
     
    Last edited by a moderator: May 1, 2017
  10. Oct 1, 2004 #9
    Dark Dimension

    This might go better in String theory, but couldn't dark matter be a fundamental 'particle' that exists in other dimensions? If all particles are vibrations of a fundamental string, then there's nothing that says there can't be particles that vibrate higher than light. But as speed of light is the measure for our space-time, we wouldn't never detect it inside our space-time. It might be curled up in compact dimensions because of it's FLT vibratory nature. Yet its effects might be inferred, such as through gravitational influence.

    Hey, it's as good as made-up particles with ultraweak interactions.
     
  11. Oct 2, 2004 #10
    Last edited: Oct 2, 2004
  12. Oct 2, 2004 #11

    Nereid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I keep promising - to myself - to investigate the data on primordial abundances, observational data on low metalicity stars, Lyman forest work, and so on, to get a richer picture of how well these constrain (rule out?) SCC (the 'Indian team's paper' says nothing useful, unless I've been reading the wrong paper).

    As we've discussed before, simply substituting baryonic DM for non-baryonic DM in a cosmological model doesn't get you very far ... the distribution of DM is, in some cases, very well known, so an alternative cosmological model still has plenty of good DM data to get its teeth into. For example, does SCC have a hierarchical approach to galaxy formation? In SCC, what sort of DM would comprise the DM in galaxy halos? If it's baryonic matter, why hasn't it been detected yet (e.g. through footprints in the misnamed galactic cosmic rays, in starbursts resulting from galaxy collisions, in microlensing searches, ...)?

    A completely different question: other than SCC, what alternative ('non-standard') cosmological models do away with non-baryonic DM? Please, only those with a reasonable degree of concordance with good observational results.
     
    Last edited: Oct 2, 2004
  13. Oct 3, 2004 #12

    Garth

    User Avatar
    Science Advisor
    Gold Member

    Try:
    D.Lohiya, A. Batra, S. Mahajan, A. Mukherjee, http://arxiv.org/abs/nucl-th/ [Broken] 9902022 ;
    Phys. Rev. D60, 108301 (2000).

    Annu: A. Batra, D. Lohiya, S. Mahajan, A. Mukherjee, Int. J. Mod.
    Physics D10, 1 (2001).

    Batra, A., Lohiya, D., Mahajan, S., & Mukherjee, A. 2000, Int. J. Mod. Phys., D9,757;

    Batra, A., Sethi, M., & Lohiya, D. 1999, Phys. Rev. D., 60, 108301.

    G. Steigman http://arxiv.org/abs/astro-ph/9601126 , (1996) is interesting too!
    good questions applicable to both LCDM and SCC models
    MOND?
    Garth
     
    Last edited by a moderator: May 1, 2017
  14. Oct 3, 2004 #13

    Nereid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Thanks.
    You are, no doubt, aware of the LCDM 'answers'!
    Not AFAIK! MOND's domain of applicability is limited; it certainly does not claim to be universal. In fact, being inconsistent with GR, it's hard to imagine how it could be modified to make it applicable.
     
    Last edited by a moderator: May 1, 2017
  15. Oct 3, 2004 #14

    Garth

    User Avatar
    Science Advisor
    Gold Member

    Yes - to invent Dark Matter and Energy!
    I quote again from Gondolo's paper:
    (Emphasis mine)

    Garth
     
    Last edited: Oct 3, 2004
  16. Oct 3, 2004 #15

    Garth

    User Avatar
    Science Advisor
    Gold Member

    There was this paper: Stacy McGaugh http://arxiv.org/abs/astro-ph/0312570
    "Confrontation of MOND Predictions with WMAP First Year Data"
    although that required a heavy neutrino (1eV), which seems to have been ruled out now.
    Although I do not advocate MOND myself, I find its lack of identifying a mechanism to explain the anomalous MOND acceleration no more disqualifying that the standard theory's lack of identifying DM particle and DE to explain its dynamics.

    Garth
     
  17. Oct 3, 2004 #16

    turbo

    User Avatar
    Gold Member

    How true! In this article:

    http://www.esa.int/esaCP/SEME3PXO4HD_FeatureWeek_0.html

    the authors explain how dark matter aligns itself very closely with the galaxies in the cluster. They propose no mechanism, and there is no observable effect from the dark matter other than the overly-strong lensing. It is perhaps too easy to measure the errors (as evidenced by excess lensing) in the standard model and attribute them to DM, and even make maps of the distribution of this mysterious stuff.

    Garth, I know that you prefer baryonic matter as DM, but what kind of baryonic matter could comprise 90-95% of the cluster mass and have NO thermal signature? (Again, IIR, you propose a much smaller percentage of DM - somewhat on the order of 30%, correct?)

    I firmly believe that we will find the zero point energy field to be the real player in this regard. Just a tiny difference in infall rates (matter vs anti-matter) could polarize the ZPE EM field in the presence of huge masses, and that polarization should affect the optical properties of space-time. The breaking of this equivalence (matter/antimatter gravitational infall rates) would also provide a mechanism for giving us a matter-dominated universe, in accordance with Smolin's black-hole universe ideas.

    The potential energy of the ZPE field is over 120 orders of magnitude too high to account for the cosmological constant, but what if that energy cannot be expressed if the field is randomly oriented? Polarization due to the presence of mass could express some of this energy, even if the infall rates of matter vs antimatter differ by a small amount. Just a thought...
     
    Last edited: Oct 3, 2004
  18. Oct 3, 2004 #17

    Garth

    User Avatar
    Science Advisor
    Gold Member

    That may be so, but what property of anti-matter would cause it to respond to a gravitational field differently from ordinary matter?

    SCC simply takes the Brans Dicke theory, which modifies GR by including a scalar field to fully include Mach's Principle, and modifies it by allowing that field to interact with matter to include the local conservation of energy. We then have a theory that satisfies present experimental tests of the EP, solar system tests of GR and a cosmology that is conformally flat, strictly linearly expansion with a total density, (densities as a proportion of critical density) of 33% of which 11% is ZPE determined by the field equations. Of the remaining 22%, about 20% is baryonic and 1 or 2 % unaccounted for, possibly a neutrino component.
    Before WMAP decreed the universe was flat and therefore of 100% density the density of the universe was generally thought to be about a third, luminous density 2%, DM for clusters 20%. ("Inflation is dead, Long live inflation", Scientific American, Science and the Citizen, July 1998 pg. 9) which fits remarkably well with the un-massaged predictions of SCC; that is if the 2% is allow to enlarge to absorb the 20% because of freely coasting nucleo-synthesis.

    I do acknowledge the problem of identifying what form the baryonic DM takes, I haven't solved all the problems at once there are some still to chew over!!

    I am interested in the weak lensing and cluster dynamics results that may be obtained if the assumption is not made that Omega-total = 1, because the WMAP apparent flatness may be explained by conformal geometry.

    Garth
     
    Last edited: Oct 3, 2004
  19. Oct 5, 2004 #18

    Garth

    User Avatar
    Science Advisor
    Gold Member

    Is it true that the DM has no signature? How dense is the IGM that produces the Lyman alpha forest? Could this be the signature of cold (~3K) gas and metals in the intergalactic voids?

    Garth
     
  20. Oct 5, 2004 #19

    turbo

    User Avatar
    Gold Member

    I'm sure my CiteBase procedure has holes in it (there is TOO MUCH to read!), but so far, I've not seen any signature of CDM cited in the literature, apart from refraction. No cited absorption, diffusion, nor spectral dispersion. CDM can't be matter, unless it the least interactive matter imaginable. ZPE fields, anyone?
     
  21. Oct 5, 2004 #20

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Another candidate hot off the presses
    http://www.space.com/scienceastronomy/astronomy/dark_matter_001004.html [Broken]
     
    Last edited by a moderator: May 1, 2017
  22. Oct 6, 2004 #21

    turbo

    User Avatar
    Gold Member

    Thank you for the link, Chronos. I'm sure you can think of one source of self-annihilating mass (hint, hint) :tongue2:

    Yes, Virginia, there is an aether. Nature abhors a vacuum.
     
    Last edited: Oct 6, 2004
  23. Oct 6, 2004 #22

    Nereid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It might be helpful to understand the DM challenge in a little more detail. For example, there is certainly a cosmological aspect - how to account for the angular power spectrum in the CMBR, universal matter density, ... - but there's also a very 'local' DM problem - cluster mass, galaxy mass, ...

    As is probably well known (at least to long-time PF readers!), MOND does a good job of accounting for several of the 'local galaxy' DM challenges (by 'local' I mean within a few hundred Mpc, say the nearest dozen or hundred or so superclusters), esp spiral rotation curves. However, it fails completely wrt rich cluster DM. Similarly, there's far too little H in the Lyman alpha forest, locally, for cold atomic H to account for cluster DM (caveat: it's probably still early days - how many detailed UV surveys have been done?). Besides, cluster IGM is very hot - as Chandra and Newton XMM results clearly show. These results also show far too little hot gas for it to be DM. Microlensing surveys (e.g. MACHO, OGLE) rule out compact objects as the DM, at least for the Milky Way halo ... where 'compact objects' is ~0.01 to 10 Msol (going from memory, it might be an even larger range).

    Oh, btw, it's the cluster DM which is the biggest headache for cosmological models, because there's apparently much more of it than galaxy DM, and rich clusters are where most of the action is.

    So, what else could the rich cluster DM be? How about a gas or plasma, but not H? IIRC, if H shows up in the Lyman forest, so will just about every other thing ... except He. While some work has been done on He in the IGM, I guess some cluster DM could be cold He (why such gas would be so preferentially enriched with He would be a new mystery, of course).

    What else?
    - dust grains? No; just as dust is easy to 'see' in a galaxy, it'd be easy to see in a cluster (and we don't see any)
    - rocks? Maybe
    - 'comets'? Maybe
    - 'loose planets'? Maybe
    However, all these would introduce pretty big elephants of their own - very peculiar size distributions (e.g. if rocks, why not lots of dust?), the origin of 'metals' in such objects (H and He alone can't form 'rocks' or 'comets'), and so on.

    How about turbo-1's favourite - ZPE, or an extension/replacement for GR in rich clusters (and heavy galaxies, and SMBHs)? AFAIK, the problem here is a lack of theory - there's plenty of good, local data that could be used to test any such theories, but where are the theories?

    When all else has been eliminated, what remains, no matter how improbable, needs to be taken seriously (who said that?). Axions and wimpzillas anyone?
     
  24. Oct 6, 2004 #23

    Garth

    User Avatar
    Science Advisor
    Gold Member

    Neried thank you for that analysis.
    The standard model has another problem with DM, it predicts that it should be concentrated in glactic centres, 'cusps', which do not appear to be there. See "Cuspy Dark-Matter Halos and the Galaxy" Binney & Evans http://uk.arxiv.org/abs/astro-ph/0108505.
    Let me give my ‘hand-waving’ scenario for general discussion and for ‘pulling to pieces’!
    .
    · The WMAP data is angular in nature, as conformal transformations preserve angles, the observation of flatness is not only consistent with the flat Friedmann model, but also with models that are conformally flat.

    · The SCC model is such a conformally flat model; it is a cone in the Einstein frame or a cylinder in the Jordan frame– either can be unrolled along their time-like axis onto a flat sheet.

    · However because these models are space-like finite the large angle WMAP anomaly is resolved, because there was not enough room for the very largest fluctuations to form; unlike the infinite flat Friedmann model.

    1. The universe consists of, (all densities are percentages of the critical density), 1% neutrino, or thereabouts –estimated from the measured light neutrino mass, 11% ZPE fields & 21% baryonic including high primordial metallicity (note this is gas not dust). No further DM is required.
    2. There is no further DE apart from the ZPE fields.
    3. The baryonic component is ¾ H and ¼ He as normal.
    4. Gravitational collapse, centred on primordial fluctuations, gradually build concentrations of gas. As the temperature and pressure of the primordial gas falls, because of cosmic expansion, so does the Jean’s mass enabling smaller gravitational collapses that will eventually form galactic super-clusters, clusters and galaxies in that order.
    5. Much primordial gas remains un-accreted in the IGN.
    6. On smaller scales within the cluster Jeans mass massive stars have accreted that go S/N and form black holes, which act as seeds around which galaxies will form.
    7. During this period there is re-ionisation of the IGN, after which the IGN continues to cool by cosmic expansion until it reaches a temperature of around 10K (??) in the present epoch.
    8. Much of the primordial gas, now ~ 25% seeded by metallicity from Type III stars and galactic out flow from Type II and I stars, remains in the IGN. The signature of this is the Lyman alpha forest.
    9. The next densest concentration is in the intergalactic cluster medium, followed by the galactic halo, which comprises of IGN still falling into galactic potential wells.
    10. The least dense concentration is in the inner galaxy where it has accreted into stars long ago hence explaining the lack of a DM galactic centre cusp.
    11. Local fluctuations of density could cause the primordial gas to form black, holes, Type III stars long expired, Type II stars – also expired(?), brown dwarfs and Jupiters.

    The actual history is going to be more complicated than this (and how!) but I offer the above as a rough template. Does it fit?

    Garth
    P.S. (who said that?) I think it was Sherlock Holmes

    P.P.S. Edit - for IGN read IGM (inter galactic medium) - why do I do that?
     
    Last edited: Oct 6, 2004
  25. Oct 6, 2004 #24

    turbo

    User Avatar
    Gold Member

    Thanks for the overview of the problems with DM candidates. None of the candidates that I found proposed in the literature (and there are a LOT of papers that I'm sure I have missed!) were satisfactory, which is why I started following the "ZPE trail" about 6 months ago. Here is where I have gotten so far, and please bear in mind that I'm discussing the EM ZPE field only at this point - particle/antiparticle virtual pairs:

    These are only the high points - there are a LOT of strands yet to be included.

    1) ZPE is pervasive, but it can be suppressed by confining the space in which the pairs can form (I.E. between the closely-spaced plates in a Casimir force instrument)

    2) The ZPE field is repulsive if the particle pairs are randomly oriented or nearly so, as demonstrated by the Casimir effect.

    3) The crux of my model is that the gravitional infall rate of antimatter is higher than that of matter. This is where I badly need sufficiently accurate testing - the Cern data are inconclusive. Note that HERE is where the equivalence of inertial mass and gravitational mass is broken. The inertial masses of each member of the virtual particle pair are equivalent, but their gravitational masses are not (due to the extra attraction of antimatter to matter).

    4) The infall rate differential causes the ZPE field to assume a preferential alignment in the presence of sufficiently large masses of matter, with the antimatter component of each pair tending to be closer to the dominating mass. Visualize a sea of magnets, then introduce a powerful monopole into the middle of them. They closer magnets would flip into alignment very readily, and the magnets farther and farther out would flip as well, being confronted with a virtual wall of aligned magnets closer back to the monopole. Now instead of magnetism, model this as matter/antimatter attraction (infall).

    5) Gravity is caused by the interaction of mass with the ZPE field. The more strongly polarized the ZPE field, the stronger the gravitational effect will be. This explains how clusters can stay together with seemingly insufficient visible matter. It should also be possible to model MOND using polarized ZPE fields in galaxies, but I'm not there yet.

    6) Polarization of the ZPE field is equivalent to increasing the density of space-time in that region - light will slow down passing through such a dense field, just like it slows down when encountering the glass lenses of a refractor. Cluster lensing in this model is therefore seen as a function of the density and shape of the lensing region, and not as a purely gravitational effect on light waves.

    In summary, exotic DM is not necessary. We already have a suspect capable of causing differential galactic rotation, cluster binding, and cluster lensing. We don't have to invent ZPE - it is demonstrably in existence. We only need to prove that the ZPE fields can be polarized by the presence of mass, and the most intuitive means by which the fields can be polarized is by a differential in antimatter/matter gravitational infall rates. If there is a differential in the infall rates, it's a whole new ball game.

    Of course, this model reintroduces the concept of the Aether, and there will be general rending of garments and gnashing of teeth as cosmologists struggle with invariance of the speed of light, no preferred reference frames and the other minor details that ensue.

    I am truly sorry that I abandoned math/physics studies in college, for I do not have time to learn the mathematics to do a proper job describing this modeling. Perforce, it's all thought experiments at this stage.
     
    Last edited: Oct 6, 2004
  26. Oct 6, 2004 #25

    Nereid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Thanks Garth.

    Perhaps I didn't say things very clearly (a situation that is, alas, rather too common); I was taking a bit of an excursion from the cosmological scale, to look at the DM challenges at 'local' scales, and to note these, irrespective of one's favoured cosmological model (of course, that favoured model may include an interpretation of we call 'galaxies' and 'clusters' as something other than gravitationally bound - more or less - bunches of stars, gas, dust, etc; if so, then we would need to have a quite different discussion!).

    In your post you use the term 'IGN', but I'm unsure whether you mean the gas between clusters, or within clusters (but not in galaxies), or both - would you mind clarifying please?

    To say a few more words about the rich cluster DM:

    In another thread we have been discussing the DM profile of a rich cluster, as estimated by the lensing of background objects. In this case, the lensing is a 'mass detector', assuming GR. The mass in a rich cluster can also be estimated by two other, independent methods - application of the virial theorem to observed cluster member velocity dispersions, and hydrodynamic calculations (assume the gas which generates the observed X-rays is in equilibrium). All three methods give roughly the same answers. So, where is the observed (dark) mass? (Segue to my previous post) ... it's not in BH/stars/gas/dust in the galaxies (there's far too little); it's not in the gas between galaxies in the cluster (maybe some caveats?); it's not in dust in between galaxies in the cluster; so where is it?

    Just in case the point I'm making isn't clear ... the question of rich cluster DM needs to be addressed no matter what cosmological model you choose to use. Also, at the risk of boring all readers to tears, only baryonic matter in the form of rocks, comets, planets and (maybe) failed stars could escape detection (other than gravitationally), and sufficient quantities of these to make up most of the rich cluster DM would imply all sorts of very odd things.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook