Dark Matter: Unseen, But Yet Again in the Limelight

The past two weeks have been busy!  I was on the road, consulting with and learning from particle experimenters and theorists at Caltech and the University of California at Irvine. And I’ve been giving talks: at the University of California Santa Barbara (for the Joe Polchinski Fest conference), at the University of California at Irvine, and yesterday in Boston at M.I.T. The Santa Barbara talk was only semi-technical, and is on-line.  The latter two, much more technical, focused on the two big projects that I completed this fall (one on whether searches for supersymmetry have been comprehensive, one on looking for unusual things the Higgs particle might do.)

While this has all been going on, there have been two big stories developing in dark matter searches, and those of you who already have heard about them will have noticed I have not written much about them yet.  (In fact I only wrote about one of them, and very partially.)  These stories are important, and also have some subtleties, which I want to make sure I understand fully before I try to explain them.  After consultations with some of the experts (including Kev Abazajian of U.C. Irvine and Tracey Slatyer of M.I.T) I’m a lot closer to that point, so an explanation will come soon, after I’ve done a bit more reading and learning.

For the moment let me just note that there are two completely different excesses —

  • one in X-ray photons (specifically photons with energies of about 3500 eV) noticed by two groups of scientists in a number of different galaxies, and
  • one in gamma ray photons (specifically photons with energies of 1 – 10 GeV [GeV = 1,000,000,000 eV]), extracted with care by one group of scientists from a complex set of astrophysical gamma ray sources, coming from a spherical region around, and extending well beyond, the center of our own galaxy.

These seem to the experts I’ve spoken with to be real excesses, signs of real phenomena — that is, they do not appear to be artifacts of measurement problems or to be pure statistical flukes. This is in contrast to yet another bright hint of dark matter — an excess of photons with energy of about 130 GeV measured by the Fermi satellite — which currently is suspected by some experts, though not all, to be due to a measurement problem.

But even if the experts are right about that, it still leaves the big question: are these excesses signals of previously unknown astrophysical phenomena, or are they signals of decaying or annihilating dark matter particles?  New astrophysics would be interesting too, but probably not Nobel-worthy, as dark matter would be.  There are arguments against astrophysical explanations in both cases, but they don’t seem by any means airtight yet.

Since the two excesses are completely different, it is highly likely that at least one of them is due to astrophysics.   [You can invent types of dark matter that would give you both signals — but it would take a small miracle for two signals of the same dark matter particles to show up in the same year.]  In fact, it is quite likely, in my mind, that they’re both due to astrophysics, not particle physics. But dark matter might show up in this way, so these excesses have to be explored fully.  It could be that this is the moment when dark matter is finally revealed.  If so — would the real dark matter excess please stand up?

69 thoughts on “Dark Matter: Unseen, But Yet Again in the Limelight”

    • Thanks for the question. Indeed, “Excess” here means “more photons of a certain type than we would have expected.” Sorry for having lapsed into jargon! It’s a constant battle…

  1. “Excesses” – pretty much the standard English meaning of the word. You get more of a signal at a particular energy than you were expecting. This could be due to random variation, measurement error, you failing to calculate what you were expecting correctly or a range of other “nothing new here” reasons.

    Or it could be due to something new. That could be a new source of an already known type, or a source of a new type. More investigation required, in any event.

    • Except that the term “excesses” was used without any previous context. And it was difficult to tell, from the article, exactly what kind of excess was brung discussed. Matt almost always a good job in structuring his articles for the non-physicists among his readers (such as myself) but he could gave been just a bit clearer in this case.

  2. You mention that it is not likely that the two excesses would be due to the same dark matter particles. But I seem to count three excesses in this post: 1) 3500 eV photons, 2) 1-10 GeV photons (GRB?) and 3) the 130-GeV photon bump. Are you discounting one of these?

  3. Years ago I read one hypothesis for dark matter is that it was from the gravitational influence of other universes hidden in higher dimensional space. Could this option still be viable?

    • Yes. There’s not much more to say about it at the moment; any type of dark matter which only interacts with us gravitationally will be pretty darn hard to detect directly and verify.

  4. “But it would take a small miracle for two signals of the same dark matter particles to show up in the same year.”

    – That’s why the year 1905 is known as “annus mirabilis”, right? Special theory of relativity, the right explanation of the Brownian motion, and the right theory of the photoelectric effect occurred not only in the same year but in the same 6-week window and they were contributed by the same person among billions of candidates.

    Two-dark-matter-particles theories of dark matter have certain problems but the two particles’ being discovered in the same year can’t be one of these problems, Matt.

    • There’s a difference between several independent discoveries being made in the same year in the same subject and having one genius solve several long-standing problems in the same year. In the latter case, there’s an obvious correlation: one genius at the center of it all. There’s no such correlation in these two excesses; completely different measurements, different places, different groups, different strategies, different implications…

      • The flipside is that there has been a size able increase in the frequency of dark matter experiments, with a large amount of experiments producing results in the last three or four years. If there was a double signal, it wouldn’t be completely crazy if it fell within this interval.

        • And…if you had some less than compelling evidence you were working to refine, you might be more likely to push it out the door (publish) if another group had already published a claim. Stimulated emission.

    • Intuitively it seems less likely that two new particles would be discovered in the same year, but I think intuition might be wrong. Scientists tend to look for things they think they can discover or rule out, and so there are currently quite a few searches for dark matter. Several of the searches are relatively new, and are just getting their data analyzed now. The searches also all tend to be at the same level of technological sophistication, so if roughly the same level is needed to discover both particles it’s likely both would be discovered at the same time. A bit like how Galileo built a better telescope and discovered four moons of Jupiter, not just one. He missed some, but discovered everything he could with the optics he had.

  5. The gravitational force attracting the matter, causing concentration of the matter in a small space and leaving much space with low matter concentration: dark matter and energy. There is an asymmetry between the mass of the electric charges, for example proton and electron, can understood by the asymmetrical Planck Distribution Law. This temperature dependent energy distribution is asymmetric around the maximum intensity, where the annihilation of matter and antimatter is a high probability event. The asymmetric sides are creating different frequencies of electromagnetic radiations being in the same intensity level and compensating each other. One of these compensating ratios is the electron – proton mass ratio. The lower energy side has no compensating intensity level, it is the dark energy and the corresponding matter is the dark matter. academia.edu/3834454/3_Dimensional_String_Theory

  6. Given the X-Ray excess could be produced by a particle with a lifetime if 10^20s making up a fraction 10^-8of dark matter, I don’t think the either/or approach is right. I agree it’s unlikely both signals have the same origin, but nothing says dark matter is just one particle – both signals could be correct.

  7. Are there any cosmologists in the house? I was under the impression that to actually generate the universe that we see, dark matter particles should be in the 1 to 10 eV range (assuming that gravity is the only long range force between them). According to neutrino oscillation theory neutrinos are not massive enough to fit the bill. But then aren’t particles in the KeV & GeV range way too massive?

        • Slightly off topic question from the Planck paper you quoted.They insist that the universe is *spatially* flat. Do they exclude the time component ? Honestly I would not know what is meant by curvature in time component, but it probably means that it is not Euclidean like the world we are familiar with.

        • Guess I must be mistaken. I thought that GeV scale energies result in galactic halos that do not jibe with galaxy rotation curves. There are fixes but they are generally considered ad-hoc. (Not sure if same applies to KeV scale – need to look into that).

          CMB determination of the sum of neutrino masses < ~.3 eV are theory laden. For example, a recent analysis of a galactic cluster found a best fit to the sum of neutrino masses ~ 4.5 eV (also theory laden).

          Actual direct experiments limit ν(e) < 2.3 eV, ν(μ) < 170 KeV and ν(τ) < 15 MeV.

          In ~2015 KATRIN will attempt to improve the experimental limit for the electron neutrino by an order of magnitude. This quote direct from the KATRIN web site: “Predecessor experiments at Mainz and Troitsk were able to appoint an upper limit to the electron anti-neutrino mass of 2.3 eV/c2. KATRIN, using the same measurement technique, will either improve this limit by one order of magnitude down to 0.2 eV/c2 (90% CL) or discover the actual mass, if it is larger than 0.35 eV/c2. This requires an improvement by two orders of magnitude with respect to key experimental parameters.”

          • Well, depends what theory you worry about. Yes, if you want direct experimental checks of neutrinos masses, the numbers you quote are correct; but the “theory” that goes into the indirect bounds from the CMB is less restrictive than the theory you’re appealing to about the dark matter.

            As for GeV particles — if what you were saying were correct, why would all this money and time and effort be spent on experiments like LUX, XENON100, CDMS, COGENT, etc? http://profmattstrassler.com/2013/10/31/questions-and-answers-about-dark-matter-post-lux/ There are various people who occasionally claim that Cold Dark Matter doesn’t fit the data, but many experts have been through the arguments many times, and these claims are never that strong.

    • Dark matter in the 1 to 10 eV range counts as a “neutrino” regardless of its underlying particle nature, if it has been around since the early universe (subject to only oscillations since then). In particular, this “thermal relic” dark matter is “hot dark matter” which can’t account for observation since it would have obliterated all large scale structure in the universe.

      Other “thermal relic” dark matter (i.e. basically, left over from the early universe dark matter particles) are either “warm dark matter” (keV mass range) or “cold dark matter” (GeV mass range or more). Originally, cold dark matter was proposed to explain dark matter phenomena and with assumptions that it is collisionless or very nearly so, cold dark matter and warm dark matter are equally good at explaining cosmology scale predictions of the kind observed, e.g., in cosmic background radiation. The critical distinction between WDM and CDM is actually mean velocity of DM particles which turns out to be a function of mass in the case of “thermal relic” dark matter.

      Real dark matter effects in galaxies tend to be best fits to spherical or better yet rugby ball shaped halos that decline in density from the center fairly gradually. Simply CDM models produce what is called a “cuspy halo” with DM density that falls off more rapidly from the core of the halo in what is called an NWF distribution, and produces fewer satellite dwarf galaxies than are observed in the universe. WDM tends to produce better fits to the astronomy data and is constrained in mass from above and below by various evidence to about 2 keV. See, e.g. H.J. de Vega and N.G. Sanchez, “Warm dark matter in the galaxies:theoretical and observational progresses. Highlights and conclusions of the chalonge meudon workshop 2011″ (14 Sept 2011) (arguing also that “Evidence that Cold Dark Matter (LambdaCDM) and its proposed tailored cures do not work at small scales is staggering.” and relying on quantum behavior of WDM at small scales that cannot be extended to CDM). One of the better ways to get CDM to fit the data better is to assume self-interactions of CDM via massive (ca. 100 MeV mass) “dark photons”. See, e.g., Sean Tulin, Hai-Bo Yu, Kathryn M. Zurek “Beyond Collisionless eDark Matter: Particle Physics Dynamics for Dark Matter Halo Structure, (15 Feb 2013) (arguing also that “there are long-standing indications that observations of small scale structure in the Universe are not in accord with the predictions of collisionless DM,”). A couple of studies have also concluded that simulations with multiple kinds of dark matter particles fit the observed dark matter phenomena less well than models with one kind of dark matter. See, e.g., D. Anderhaldena, et al. “Hints on the Nature of Dark Matter from the Properties of Milky Way Satellites” (12 Dec 2012) and J. Viñas, et al. “Typical density profile for warm dark matter haloes” (9 Jul 2012).

      In the case of non-thermal relic dark matter (e.g. axions) the mass limits are less strict since mass and average particle speed aren’t as tightly related to each other. Its behavior as “hot”, “warm” or “cold” dark matter, and its cosmology impact depends in a model specific way on how its ongoing production and destruction occurs. Thus, for example, axions can have WDM average velocities despite having sub-10eV masses.

  8. First, this is not spam.

    Second, Premise: The finite resides in the infinite and not the other way around.

    Dark matter is time/space and was created as the initial implosion just prior to ignition at big bang when space/time came into existence as the rebound from the most first implosion. Dark matter is time phased resting potential that appears as a mirror image of space/time where antimatter is the active component of dark matter.

    There is no super symmetry as expressed in failed CPT theory but is that vacuum resting potential that produces and refines space/time matter at the boundary layer or Higgs Field through the mechanism of the time phased and mirrored dark matters active component as antimatter.

    Space/time matter seeks to return to the quiescence of resting potential as absolute vacuum and is gravity while it is repelled by time/space dark matter or infinite potentiality and is antigravity which reduces the strength of gravity and together are Gravity.

    The electromagnetic force which derived from the electro weak force in Planck time is produced by the interaction and fluctuations of gravity and the time phased antigravity that predates space/time as the bang by less than Planck time, but still exists slightly in the future and describes “spooky at a distance” phenomenon and relativistic entanglement and suggests time travel which is not possible as the universe currently exists.

    If the two opposed forces inherent in Gravity were to combine again as they were at the most first and most finite implosion/explosion or crunch/bang the universe would again explode and dissolve back into absolute vacuum from whence the most first movement originated at the OM point. At which time, Light divided from shadow and formed the most finite that is producing an infinite number of finite, infinitely expanding infinite universes as the multiverse.

    Trillions of years from now these infinite number of infinite universes will coalesce into an infinite dream state to push for exhaustion of motion when everything knows everything, which all is extant within the Infinite Intelligence.

    As an aside, dark energy is really the repulsive force of gravity which is best described as black holes and dark gravity objects which increase in number by one each day as the product of super novi imploding throughout the cosmos where the number of these objects is directly proportional to the increasing velocity of the expansion of the kinetic space/time universe where our space is the time of the time/space universe of potentiality and our time is the space of the time/space resting potentiality and driven by the interactions between matter and antimatter as the active principle of dark matter which reconditions and creates new particle wave fields such as the three generations of matter were produced in the younger flat universe we inhabit due directly to the formation of heavier elements that allow the evolution of our bodies which house our spiritual souls that involve and return to the infinite, consciously through the three worlds and seven stages or planes of consciousness. I do not apologize for my long sentences.

    • This is simply the second excess that I referred to in this post. The proposed 30 GeV particle would give a signal of photons in the 1-10 GeV range, which (if this were correct) would give the second excess. Unfortunately the article you refer to is almost content-free and so it doesn’t explain anything.

  9. On page 185 of the Doc 30 Foundation of the General Theory of Relativity Einstein said the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy. And yet there seems to be a big assumption that “dark matter” is perforce made up of particles, even though it’s a concentration of energy that causes gravity. This can be field energy. A gravitational field isn’t made out of particles.

    • Yes, gravitational fields gravitate; that’s why there are black holes. But gravitational fields that are not in black holes do not form clumps, while dark matter (observationally) does. Particles would clump, as would black holes; but gravitational waves do not. That is why particles and primordial black holes are potential dark matter candidates, while other forms of gravitational fields are not.

      Sometimes, it pays to actually work through the equations, not just read the words. Actually, “sometimes” = “always”.

          • Indeed-but, since the subject has been raised, I looked around and found this; http://arxiv.org/abs/1301.5971, “A new probe of dark matter properties: gravitational waves from an intermediate mass black hole embedded in a dark matter mini-spike”, that may be of some interest.

          • So, while gravitatonal waves aren’t suitable as such, to describe dark matter, they may provide interesting *probes* for detecting dark matter.

      • A particle need moment of inertia. Macro bodies make curve in spacetime grid. If we place a grain of same mass, as macro body, on a single thread of the grid, it will not make a spacetime curve – here spacetime is more strong than low energy (mass) – gravity effect is negligible.
        If the frequency of that “grain” is increased (high energy), then spacetime thread will bend – but without moment of inertia there is no mass or particle. Again gravity increases as distance shortens ?
        So gravity is related more to momentum rather than energy ?

        In primordial black hole evaporation, the dark matter is still a particle, because it still obey the relativity.
        Dynamical friction of dark matter on clumps of baryonic matter has the general effect of transforming angular momentum from the baryons to the Dark matter – because dark matter is below absolute-zero temperature. But entropy decreases due to increase of mass at more “lowest-energy state” and increase of volume of space due to evaporation ?

      • The gravitational field is just the starting point. Think ΛCDM but then think conservation of energy and the raisin-cake analogy. Space expands between the galaxies but not within, so every galaxy has a halo of inhomogeneous space where the energy density varies, so Λ isn’t constant. The see Einstien’s Leyden Address. Inhomogeneous space is what a gravitational field is.

        • Uh-huh. You ought to study the cosmic microwave background more carefully. Just because Einstein said something doesn’t mean it’s right; and if the data contradicts what you say, then what you say is wrong.

        • The raisin cake analogy is intended to convey one thing: How in an expanding universe each galaxy would observe all the distant galaxies moving away from them without this implying that any one of them is the ‘center’. Do you understand this? Then STOP thinking about the raisin-cake ANALOGY.

          Space expands within the galaxies due to the cosmological constant. However this expansion is very weak on this scale, and so easy counteracted by gravitational attraction. The energy density does not change as space expands — you have to think more carefully about conservation of energy in the context of general relativity to see why this isn’t a problem.

  10. ‘The wall of darkness’. said Ildefonse, ‘is “Nothing”; your world is floating towards it irrevocably; any further ado here is senseless’. (Morreion, Jack Vance)

  11. Just one point of clarification, the 2nd excess of ~1 to 10 GeV in the Galactic Center has been around for some time, with preliminary results in a 2009 preprint, arXiv:0910.2998, then in published work arXiv:1010.2752. Our UCI group discovered the signal with high significance in 2012, arXiv:1207.6047, and refinements of the analyses have characterized its properties with increasing precision: arXiv:1306.5725, arXiv:1402.4090, & arXiv:1402.6671.

    • I would agree with Kev here – this wouldn’t be two discoveries in the same year, but really separated by a few years. The probability that they are both DM is of course still small, but because the probability that even one is DM is small (I say that as a strong optimist, as you know).

      The temporal coincidence of the attention I think may have something to do with the UCLA DM conference, for which people tend to save and then highlight their results. That’s speculation, though.

  12. There is no such thing as non-baryonic dark matter anchored to matter. Matter moves through and displaces the aether.

    What is referred to as the Milky Way’s dark matter halo is the state of displacement of the aether.

    Displaced aether pushing back and exerting inward pressure toward matter is gravity.

    The state of displacement of the aether *is* gravity.

    • Explain what occurs physically in nature for any one of the following.

      ‘Galactic Pile-Up May Point to Mysterious New Dark Force in the Universe’

      “The reason this is strange is that dark matter is thought to barely interact with itself. The dark matter should just coast through itself and move at the same speed as the hardly interacting galaxies. Instead, it looks like the dark matter is crashing into something — perhaps itself – and slowing down faster than the galaxies are. But this would require the dark matter to be able to interact with itself in a completely new an unexpected way, a “dark force” that affects only dark matter.”

      It’s not a new force. It’s the aether displaced by each of the galaxy clusters interacting analogous to the bow waves of two boats which pass by each other.

      ‘The Milky Way’s dark matter halo appears to be lopsided’
      The Milky Way’s ‘dark matter halo’ is lopsided due to the matter in the Milky Way moving through and displacing the aether.

      ‘Offset between dark matter and ordinary matter: evidence from a sample of 38 lensing clusters of galaxies’

      “Our data strongly support the idea that the gravitational potential in clusters is mainly due to a non-baryonic fluid, and any exotic field in gravitational theory must resemble that of CDM fields very closely.”

      The offset is due to the galaxy clusters moving through the aether. The analogy is a submarine moving through the water. You are under water. Two miles away from you are many lights. Moving between you and the lights one mile away is a submarine. The submarine displaces the water. The state of displacement of the water causes the center of the lensing of the light propagating through the water to be offset from the center of the submarine itself. The offset between the center of the lensing of the light propagating through the water displaced by the submarine and the center of the submarine itself is going to remain the same as the submarine moves through the water. The submarine continually displaces different regions of the water. The state of the water connected to and neighboring the submarine remains the same as the submarine moves through the water even though it is not the same water the submarine continually displaces. This is what is occurring physically in nature as the galaxy clusters move through and displace the aether.

      Thank you for choosing to remain ignorant of understanding what occurs physically in nature.

        • I must have missed where you explained why dark matter which was theorized to barely interact with itself is now seen to pile-up.

          I must have missed where you explained why the Milky Way’s halo is lopsided.

          I must have missed where you explained why there is an offset between the light lensing through the space neighboring galaxy clusters and the galaxy clusters themselves.

          All correctly explained and easily understood by understanding aether has mass and is displaced by the particles of matter which exist in it and move through it.

          “The word ‘ether’ has extremely negative connotations in theoretical physics because of its past association with opposition to relativity. This is unfortunate because, stripped of these connotations, it rather nicely captures the way most physicists actually think about the vacuum. . . . Relativity actually says nothing about the existence or nonexistence of matter pervading the universe, only that any such matter must have relativistic symmetry. [..] It turns out that such matter exists. About the time relativity was becoming accepted, studies of radioactivity began showing that the empty vacuum of space had spectroscopic structure similar to that of ordinary quantum solids and fluids. Subsequent studies with large particle accelerators have now led us to understand that space is more like a piece of window glass than ideal Newtonian emptiness. It is filled with ‘stuff’ that is normally transparent but can be made visible by hitting it sufficiently hard to knock out a part. The modern concept of the vacuum of space, confirmed every day by experiment, is a relativistic ether. But we do not call it this because it is taboo.” – Robert B. Laughlin, Nobel Laureate in Physics, endowed chair in physics, Stanford University

          Matter, a piece of window glass and stuff have mass.

          In a double slit experiment it is the stuff which waves.

          “any particle, even isolated, has to be imagined as in continuous “energetic contact” with a hidden medium … If a hidden sub-quantum medium is assumed, knowledge of its nature would seem desirable. It certainly is of quite complex character. It could not serve as a universal reference medium, as this would be contrary to relativity theory.” – Louis de Broglie, Nobel Laureate in Physics

          “According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense.” – Albert Einstein, Nobel Laureate in Physics

          The relativistic ether referred to by Laughlin is the hidden sub-quantum medium referred to by de Broglie is the ether which propagates light referred to by Einstein.

          A moving particle has an associated aether displacement wave. In a double slit experiment the particle travels through a single slit and it is the associated wave in the aether which passes through both.

          We’ve already detected gravitational waves.

          ‘Hubble Finds Ghostly Ring of Dark Matter’

          “Astronomers using NASA’s Hubble Space Telescope got a first-hand view of how dark matter behaves during a titanic collision between two galaxy clusters. The wreck created a ripple of dark mater, which is somewhat similar to a ripple formed in a pond when a rock hits the water.”

          The ‘pond’ consists of aether.

          The galaxy clusters are moving through and displacing the aether analogous to the bow waves of two boats which pass by each other very closely.

          The ripple is an aether displacement wave.

          The ripple is a gravitational wave.

          What ripples when galaxy clusters collide is what waves in a double slit experiment; the aether.

          Einstein’s gravitational wave is de Broglie’s wave of wave-particle duality; both are aether displacement waves.

            • The state of mainstream physics, understanding what occurs physically in nature is referred to as garbage.

              • The state of crackpot physics, unable to recognize that mainstream physics predicted the W and Z (discovered!), the top quark (discovered!), the Higgs boson (discovered!), the peaks in the cosmic microwave background (discovered!), and a host of other things. All you have is words; we actually have equations, papers, precise predictions, careful comparison of data with those predictions, and a host of other things.

                Now, if you want to learn something about science, you are welcome here. If you want to advertise your wares and your own crackpot theory, put up your own website; no one is entitled to advertise here — even I don’t advertise my own theoretical ideas here. If you want to berate me and other physicists for the incredibly lousy job you think we’re doing, you’re entitled to your opinion, but you’re not entitled to make a mess of my website… so in that case, please leave.

                • Explain what occurs physically in nature to cause gravity or the observed behaviors in a double slit experiment.

                  Can’t, can you?

                  All because you insist on not understanding aether has mass and is displaced by the particles of matter which exist in it and move through it

                • ‘[1305.5759] Comment on higher derivative Lagrangians in relativistic theory’

                  “The relativistic theory of an Aether was discussed several time, see for e.g. [8], [9]. In this paper, our hypothesis is different and gives a relativistic theory of the deformation of continuous media (for which the geometry is described by the metric field).”

                  The Milky Way’s halo is the deformation of continuous media.

                  The Milky Way’s halo is curved spacetime.

  13. The experimental fact thus far is that DM particles interacts with matter via the gravitational interation. This may suggest that a DM particle is a particle of pure gravity ie the long sought graviton.The question then naturally arises as to why does it manifest only at large scales and not microscopic levels?I am of the opinion that DE and DM hold the answer to quantum gravity.

    • I’m afraid this is manifestly wrong. Gravity is a very long-range force, like electromagnetsm; therefore the graviton is massless, like the photon, and travels, like the photon, at the universal speed limit (i.e., c, often called “the speed of light”, but in fact the speed of anything massless.) Gravitons could only give dark radiation, just as photons give visible radiation. They cannot give dark matter, which, from the existing data, must be due to particles whose velocity is well below the speed of light.

      By the way, don’t you think physicists would have thought of that idea already, if it could have worked? We’ve had 50 years to consider the possibility…

      • The current quantum description of gravity using the graviton paradigm you describe is flawed and for that reason we still, after 50 years, have no self consistent quantum theory of gravity. A new type of graviton is needed to provide a self consistent model. One as topologically different from the orthodox model as an orange is from a doughnut.

      • If you are looking for physics beyond the standard model a good start is to discard the current graviton picture and seek one that best fits the observable facts.

        • Such as gravity’s long-range nature? If you’re throwing out all of special relativity and quantum mechanics, why call this thing a ‘graviton’ anyway?

  14. If dark matter particles are much more massive, they might produce signals in the ultra-high-energy cosmic rays. Neutrinos and neutrino-like particles (popular in Hot and Warm Dark Matter models) can have weak interactions.
    Weakly Interacting Massive Particles: Also known as WIMPs, these particles, by definition, meet all the needs of CDM.
    Here what is the “weak interaction” of non-baryonic dark matter with the clumps of baryonic matter ?

      • Thank you Professor,
        in this context (weak nuclear force), this statement **Dynamical friction of dark matter on clumps of baryonic matter has the general effect of transforming angular momentum from the baryons to the Dark matter** have any meaning ?

        • ….because like the same is mathematically consistent in W and Z bosons get their masses from a heavy particle called Goldstone bosons by Spontaneous symmetry breaking – why not for baryons from DM particles ? (Is it correct ?)

  15. Thank you for every other informative blog. The place else may
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  16. The state of mainstream physics, correctly understanding what occurs physically in nature is described as garbage.

  17. ‘[1305.5759] Comment on higher derivative Lagrangians in relativistic theory’

    “The relativistic theory of an Aether was discussed several time, see for e.g. [8], [9]. In this paper, our hypothesis is different and gives a relativistic theory of the deformation of continuous media (for which the geometry is described by the metric field).”

    The Milky Way’s halo is the deformation of continuous media.

    The Milky Way’s halo is curved spacetime.

  18. Let’s think every single cell of vacuum at Planck scale must have causal relation with all observers concerned with changes in curvature or in virtual motion schema at conventional gravitational potential states.

    As net force field we seem to get DM halos, don’t we.

    there do not have to be restriction of quantized cell scale but maybe there will be because of quantum mechanics and uncertainty principle…

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