Pavel Kroupa on “The vast polar structures around the Milky Way and Andromeda “

22 November 2013 by Marcel S. Pawlowski, posted in Talk

In case you, like me, have missed Pavel Kroups's recent talk at the Joint Astronomical Colloquium in Heidelberg, you now have the opportunity to watch a movie of the event and download the slides. The movie is quite long (more than an hour), but it is worth watching it to the end. While the talk is titled "The vast polar structures around the Milky Way and Andromeda", Pavel talks about much more, starting with tidal dwarf galaxies and ending with a discussion of indications for an alternative model of gravity.

This presentation is very similar and in most parts identical to Pavel's presentations held at Monterey at the conference "Probes of Dark Matter on Galaxy Scales" and in Durham at the "Ripples in the Cosmos" conference. The latter talk resulted in quite a discussion on Peter Coles' (aka Telescoper) blog "In the Dark", following his criticism of Pavel's talk as being "poorly argued and full of grossly exaggerated claims". The video of a very similar presentation now offers everybody the opportunity to develop their own opinion on the issue. Given the numerous questions Pavel got during his talk and afterwards, people must have thought that it was worth the effort to argue with him, in contrast to Peter's opinion.


33 Responses to “Pavel Kroupa on “The vast polar structures around the Milky Way and Andromeda “”

  1. ThomasM Reply | Permalink

    If I undestand the presentation correctly one key point it that the tullIy fisher relation is not reproduced by models with dark matter. I had a look on the talks given at the Montery conference and there was a presentation by R. Reynes

    http://adsabs.harvard.edu/abs/2013pdmg.conf40304R coming to the opposite conclusion, tully fisher and standard model of astrophysics are going well together.

    So, how to explain this controvesial conclusions?

    Thomas

    • Stacy McGaugh Reply | Permalink

      It is always possible to fit a dark matter model to data. That is not the same as the data being predicted by the dark matter paradigm. No dark matter model successfully predict the observed Tully-Fisher relation a priori.

      The specific model to which you refer is appears to be a post-facto fit. (I can't really tell from just the abstract you link.) It seems like a perfectly respectable effort, but it is careful to note that it covers a modest range of the data - just two decades in stellar mass. It does not address the 3 additional decades to lower mass that were correctly predicted a priori by MOND.

      More generally, there are lots of claims out there that Tully-Fisher is consistent with this or that model. However, none of them share the predictive success of MOND on this topic. Most of them predict the wrong thing. The best that one can hope to achieve is to reproduce post-facto what MOND predicted a prioiri.

    • Pavel Reply | Permalink

      Thomas, thank you for your important question. Stacy McGaugh already provided the answer, namely, that the Tully Fisher Relation (TFR) was not predicted by the dark matter ansatz. It was predicted by Milgromian dynamics though, decades beofre it was verified observationally at the low mass end. As Stacy explains, much effort has been going into accounting for the TFR within the standard dark matter model, and the abstract you point out by Reynes is such a recent attempt. Reynes presentation in Monterey was very good, and yes, this work constitutes an important contribution. But if you read the abstract, you will note that the "primary remaining freedom in the mass models come from the final dark matter halo profile". That is, the dark matter halo needs to be adjusted in order for the models to lie on the TFR. Milgromian dynamics does not have this freedom. In Milgromian dynamics, matter orbiting within a self-gravitating disk is forced, by natural law, to move such that the system obeys the TFR (by obeying Milgroman dynamics). In the dark matter hypothesis, the circular motion of the matter depends on the dark matter halo via Newtonian dynamics. However, the baryonic mass of a galaxy does not obey a one-to-one relation with the dark matter halo mass. This is so because each dark matter halo has a different and individual merging history with other dark matter halos and an individual accretion history, in order for it to grow to a sufficient mass to accommodate a galaxy with a given baryonic mass. Thus, for a given baryonic mass, galaxies have a range of peak or asymptotic circular velocities, given that the halos differ among such galaxies. Furthermore, the dark matter halos are typically triaxial, and the resulting range of orbital speeds even for one and the same galaxy thus shows an appreciable scatter for a given baryonic mass of a galaxy. In contrast, the observed, real TFR shows a small spread, which is consistent with the measurement uncertainties, i.e., it is consistent with there being no scatter at all apart from the differences casued by different stellar populations at a given galaxy luminosity. Last not least, the observed TFR extends into the dwarf galaxy regime down to little galaxies which have a mass comparable to a massive globular cluster. That the TFR remains so extremely well defined at these very small masses, where the galaxies are have major gas fractions, constitutes one of the greatest triumphs of Milgromain dynamics, and possibly one of the greatest failures of the standard dark matter model, which has, to my knowledge, not been able to reproduce this extremely tight correlation between baryonic mass and circular motion at the low-mass end. To explain this a little further: Imagine you have two identical dark matter halos. In the one the galaxy evolves into a star burst such tha the baryonic mass (and partially the innermost dark matter mass) are redistributed somewhat. The brightness of the post-star burst galaxy will then differ from the other galaxy which did not have such an epoch. But the asymptotic circular velcity is defined by the dark matter halo, and is thus the same in both galaxies. In Milgromian dynamics, irrespective of whether a galaxy evolves through a star burst or not, it will at all times and due to natural law lie on the TFR, unless it is perturbed dynamically, e.g. by a passing galaxy. Real galaxies thus clearly obey a law of nature, while dark matter model galaxies need to be heavily fine-tuned to lie on the observed TFR, but it is not known how this fine tuning ought to occur with realistic physics to achieve this.

  2. ThomasM Reply | Permalink

    Stacy, Pavel,

    thanks a lot for your detail replies. Just to get one final point right, the tidal dwarf galaxis fall on the TFR, but there is no model with dark matter which can acount for that. So my question, how reliable are these points?

    Thomas

    • Pavel Reply | Permalink

      Thomas, measurements can always be prone to error and it is desirable to get more data points, i.e. TDG rotation curves. But, to have three TDGs lying so close to the TFR is very improbable if the measurments were subject to major uncertainty or error. The TDGs would then lie somewhere in the baryonic-mass--circular velocity plot, with a bias towards significantly lower circular velocities in the Newtonian framework since they cannot contain much dark matter. Thus, the brilliance of the original Bournaud et al. contribution, where the TDG data were published, lies in providing three of them, rather than only one TDG. Still, we need more well studied cases. I expect astronomers working in Europe will be providing such data in due time, given that such fundamentally important but not-main stream research appears to be, until now, difficult if not impossible elsewehre - but why would this be the case?.

  3. David Brown Reply | Permalink

    "It is always possible to fit a dark matter model to data."
    I now have 2 decisive empirical tests for my quantum theory of gravity.
    http://vixra.org/abs/1312.0193 “Is the space roar an empirical proof that the inflaton field exists?”
    On 12/20/13 5:17 AM, David Brown wrote:
    Prof. Witten: Do you have an opinion concerning the comments posted for?
    http://quantumfrontiers.com/2013/11/05/fundamental-physics-prize-prediction-green-and-schwarz/
    — D. Brown

    On Fri, Dec 20, 2013 at 3:54 AM, Edward Witten wrote:
    I am generally sympathetic with these observations
    Edward Witten

  4. ThomasM Reply | Permalink

    Coming back to the quesion of the Tully-Fischer Relation. Spheriodal dwarf galaxies are accroding standard cosmological models strongly dark matter dominated, there are some very low luminousity dwarfs whith dark matter content of 99 % or even more. I would not expect them to fall on the baryonic TFR, can their dynamics be explained within models with theories of modified gravity?

    Thomas

  5. Marcel S. Pawlowski Reply | Permalink

    The Tully-Fisher relation only applies to rotationally supported galaxies, so it is not applicable for dwarf spheroidals. However, it is possible to predict the velocity dispersion in these dwarf galaxies using MOND. Recently this has been done for the satellite galaxies of our neighboring Andromeda galaxy (http://arxiv.org/abs/1301.0822) and the results are in very good agreement with the observed values (http://arxiv.org/abs/1308.5894).

  6. David Brown Reply | Permalink

    Marcel, Pavel, Stacy & other MONDites:
    I now have THREE decisive empirical tests for my quantum theory of gravity.
    When gravitational accelerations are low, Milgrom's acceleration law is APPROXIMATELY equivalent to the Fernãndez-Rañada-Milgrom effect BY AN EASY SCALING ARGUMENT — just mathematically. However, it is not clear what is going on in terms of physics.
    There are 2 possibilities: (1) Newton-Einstein gravitational theory is 100% correct but appears to be wrong for some unknown reason. (2) Newton-Einstein gravitational theory is slightly wrong (probably because of quantum gravitational effects).
    Google "space roar dark energy". I think I may have persuaded Witten that Milgrom is the Kepler of contemporary cosmology. (UNFORTUNATELY I HAVE SHOT MYSELF IN THE FOOT BY MAKING SEVERAL STUPID MISTAKES.) MONDites need to persuade at least one string theorist that non-relativistic MOND is empirically valid. Much money and many prizes are at stake. MOND is the key to understanding string theory.

  7. David Brown Reply | Permalink

    A thought for MONDites: There is strong opposition to MOND. Several astrophysicists have won the Dannie Heineman Prize in Astrophysics for their work on dark matter particles. As of Jan. 2013 I think that I am actually beginning to understand string theory and quantum gravity. The Lambda-CDM model is wrong for at least two reasons: MOND and the space roar. The space roar has no huge lobby of mistaken opponents ... food for thought.

  8. OprhanIsland Reply | Permalink

    Hi Krouopa and Pavel,

    I was directed hee by one of your fans, I'm a software engineer not a Quantum Engineer, but have been tinkering with Quantum Theory since I was 12.

    After watching Kroupas' presentation I have this these responses / questions ...

    I like your maths and the observations, but one thing you don't allow for is how do the original galaxies form ?

    Based on observation we know that Dark Matter is continuously degrading to smaller particle sizes, these interactions that Kroupa is talking about imply that the Dark Matter no longer exists in a form that can interact in any significant way with the galactic matter.

    I agree with your statements that Dark Matter is not evident in these galactic reactions, I disagree that Dark Matter is falsified.

    I'd be interested to hear what his take on the Higgs Boson is, considering it is a proof of particle interaction at zero G particle size level(s).

    Further, the fact that these galaxies collide in the first place implies that the dark matter halo has degenerated already, well before they collide.

    The one example I have for the formation of galactic matter, is the Boomerang Nebula, I'm sure there are more already observed. Again I'd be very interested on your opinions on the observed output(s) of this Nebula.

    The biggest obstacle we face with dark matter is calculating it's degradation rates, and the variables involved, The Boomerang Nebula for instance is regarded as the coldest observed space so far, which makes absolute sense when looking at the degradation speed, and the requirements of larger particle and molecule formations.

    • Pavel Reply | Permalink

      Hello OrphanIsland,

      the dark matter effect is not falsified - the dwarf galaxies near the Milky Way, those near Andromeda and disk galaxies show clear signes that this effect is there. It is deduced by observing that the stars and, if present, the gas move at velocities far larger than should be the case in the absence of "dark matter". That is, "dark matter" has not degenerated away. The point is that the hypothesis that this dark matter effect is due to elmentary particles which do not interact with each other significantly apart from their gravitating effect, leads to well-understood predictions of the shapes of the dark matter halos which from from cosmological structure formation and within which galaxies _must_ be embedded if this hypothesis is correct. Some of my colleagues may want to argue that there are not good predictions and that there are too many uncertainties (I know this from experience), but this is not correct given the large body of published results (which would have to be false, if the argument were true, in which case we have no cosmological theory as predictions can then not be made if the "theory" is so uncertain - the scientific process breaks down because mere "notions that there is some sort of dark matter" cannot be falsified). So, given the results we have based on pulbished work from hundreds of researchers in many teams world wide, these can be compared to the observations, and they are found to be highly significantly discrepant on basically every test performed to date involving galaxies. The observations cannot be discarded, so the theory must be discarded. The "dark matter effect" must however account for the observations, and the work of Milgrom has already, since decades, been showing how they can be understood. His approach has not been falsified to date.

      • OrphanIsland Reply | Permalink

        Thanks for the reply Pavel, and very interesting work, I have no problems with MOND as it is still describing emperical evidence, so the calculations must be sound.

        The problem I see is the "Imbedded" and "Halo" descriptions, from what I have observed the dark matter resides in a much larger structure and the galactic matter resides in a concave depression "on" the dark matter surface, the dark matter itself has varying degrees of interaction densities within the galaxy formation itself.

        I also see evidence of these dark bodies under virtually every observed galaxy to date, although in some observations the dark body has obviously degenerated to much smaller particle sizes, there is still evidence of it's previous interactive existence.

        The Boomerang nebula is a perfect description of this, from what I can see there are at least two extremely large (radius of at least 12 or more times the galactic matter it's creating) dark bodies interacting with each other and the Galactic matter is forming because of this interaction.

        I'm still interested on your take on the Higgs, as well as the apparent fluctuations in the Gravity constant experiment on earth that have recently been published.

        Power too you Pavel and friends :-)

        PS: Based on your response, can I assume you are not supporting the "Electric Universe" any more than an abstract theory at this point ?

  9. Daniel Jencka Reply | Permalink

    As a long time follower of astrophysics, cosmology, and science in general, I have found your work on an alternative dark matter hypothesis quite fascinating, and especially since you are arguing that it has failed. I have a couple questions.

    1. Following your claimed falsification of the dark matter hypothesis, I have come across only a few reactions by scientists on the internet, and the response seems to be that falsifying the hypothesis may be all well and fine, but because MOND has not yet been shown capable of explaining the motion of objects at the largest scales, the best thing is just to keep plugging away at the standard model. Properly, one would think that objectively refuting your falsification would be the first order of business to those adhering to the standard model. If unable to do so, then shouldn't they at least justify that there is some kind of sound scientific practice for their continued pursuit of a falsified hypothesis? (Surely, it can't be just psychological and institutional momentum.)

    2. If the standard model is in your opinion falsified, that would of course add scientific justification to pursuing some hypthesis involving MOND, but if all MOND-involving hypothosese fail, what else is out there?

    Thank you in advance for your response.

  10. Daniel Jencka Reply | Permalink

    Meant to say "an alternative to the dark matter hypoyheses..."

  11. Daniel Jencka Reply | Permalink

    And a 3rd question: I have seen some mention that some MOND-based approach may be compatible with a dark matter approach. Is this kind of hybrid explanation a possibility for you after having falsified the dark matter component of the standard model? (Please pardon my various typos. I have a center vision problem coupled with dyslexia, making it only somewhat successful to proof read my own writing.)

    • Pavel Reply | Permalink

      Hello Daniel,

      thank your for your comments.

      Yes, I am very aware of the fact that the majority of established scientists (at the moment) "feel" the falsification cannot be taken too seriously. But this is irrelevant, because the laws of gravitation are impervious to what the majority of established scientists think or feel. In any case, it is important to be sceptical, and reluctance to immediately agree with one scientisits "falsification" is a healthy aspect of rigorous science.

      It has been argued, on behalf of the existence of dark matter particles, that there are successful precedents in history in which previously unseen matter has been introduced in order to explain physical phenomena (e.g. the neutrino, the planet Neptune). But, there are equally historical precedents in which material has been postulated which was found to not be physical, that is of obsolete scientific theories (e.g. phlogiston, ether).

      Even if perhaps the majority of my colleagues, at the moment, do not take the falsification seriously, it is important for me as a scientist to publish my findings and to report them if I am convinced they are true, and to use these insights for steps towards understanding the observed universe more thoroughly. My own aim is that I want to understand nature, and established thinking is useful and important in doing so, but if it is wrong then new avenues one must seek. In this sense it can be irrelevant what others say or do, but it does become arduous to have to work against flawed counter-arguments [see e.g. this research paper by Ibata et al. 2014 ,
      which corrects major if not silly errors which have been circulating in the (in this case too uncritical) community as an argument that the satellite galaxy arrangement around Andromeda is "common" in the cosmological models]. Such counter-arguments are one reason why the community is discouraged to agree with the falsification, and this is why flawed counter-arguments are so damaging. They make-belief that a problem (in this case the disk-of-satellites) does, after all, arise naturally within the standard framework.

      It is thus required to work-out rebuttals of the flawed counter-arguments (in this case as done excellently by Ibata et al. 2014), but this costs time and the rebuttals unnecessarily freeze research efforts. While to write rebuttals is an essential part of the scientific process when good arguments are brought up, for example in the form of new observations which at first sight might appear discrepant to, say, the falsification or some other argument it is based on, it becomes damaging if the counter-arguments are based on very poor work which a referee accepts for publication, perhaps either because the referee does not understand the material, or because of some other reasons. It becomes totally destructive if there are, at a similar time, a number of flawed counter-arguments, which cannot be dealt with any longer given the resources at disposal.

      The answer to your point (essentially that a falsification is not valid if no alternative, fully fledged theory exists which can already account for all cosmological observations) is thus that this is the wrong way to do science.

      A scientist may well discard a theory, given robust statistical tests based on observations, in order to free herself/himself from the old burden and to then embark on trying to find a better theory. This same scientist does not need to wait until the rest of community catches up.

      It is also the wrong way to do science because the sheer huge amount of now existing observational material cannot be dealt with by a small team who may propose an alternative description or theory. It takes time and resources to test a new theory as rigorously as an old one, and if the resources are not available because of the very argument you are bringing up (i.e., we invest into a new theory only if it is shown to be compatible with all the data) then the scientific process grinds to a stop. Many papers can still be written, much activity can proceed, and much money be used up, by many minor contributions which do not advance our understanding significantly, but the big step can then not be done.

      Concerning your second question (what if the alternative, Milgromian dynamics, fails): First of all, we are testing Milgromian dynamics as vehemently as the Einsteinian/Newtonian plus dark matter approach (which is falsified). The hardest test for MOND devised so far to my knowledge has been developed by my team in Bonn: Baumgardt et al. 2005: If Milgromian dynamics is correct, then it must obviously also hold in globular clusters. So far the observational tests that have been performed by measuring the line of sight motions of stars in relevant globular clusters have led to a null result. That is, there is no clear signature of Milgromian dynamics in these systems, although we expected this to be the case. However, this does not yet constitute a falsification of Milgromian dynamics, because the observations are extraordinary difficult to make and important errors can and have been occurring, and furthermore, Milgromian dynamics has not been formulated yet for the case of relaxational systems. This situation is embodied in the theory-confidence graph (fig. 16 in the falsification paper).

      If Milgromian dynamics is falsified, then this can only mean that the particular formulation existing today disagrees with the data, but Milgrom's laws will still hold true as empirical laws which galaxies follow (today by empirical evidence). Any new theory of gravitation, which may be Einsteinian with hitherto unknown physics of the vacuum, or some completely new approach to gravitation, will have to account for these laws.

      But why am I so certain that the standard model of cosmology is falsified (that is, that there is no cold or warm dark matter), but that Milgromian dynamics is not yet falsified? Am I not being one-sided and biased here by discarding the one over the other? Why would I want to do this, as politically it makes life harder to go against the standard line and to question authority
      (Peebles 2013 ). Such a stand does have career-implications.

      The falsification of the standard model of cosmology (to be more precise, of the existence of cold or warm dark matter particles) is very robust indeed. It is completely consistent with all existing data. The falsification paper contains a major effort in consistency checks. If the falsification, based on the dual dwarf galaxy theorem, is true, then this conclusion must be consistent with other data. An important consistency argument is the highly significant disk-like distribution of satellite galaxies around the Milky Way and Andromeda. But other consistency arguments are also available, such as the mass-discrepancy--acceleration correlation, the empirical violation of the theoretically expected mass--luminosity relation for dSph/UFD satellite galaxies, that dynamical friction makes dark-matter solutions for the orbits of the dSph satellites difficult if not impossible, the observed result that merging does not seem to be a significant driver of galaxy evolution because the vast number of galaxies more massive than about 10^{10}Msun are much simpler than thought, etc.

      Concerning the third question: yes, there are such very interesting suggestions. I have not tested them against available evidence, and it is important to work-out any theoretical approach to the gravitational problem on galaxy scales and beyond. My personal impression though is that hybrid approaches make the theory more complicated. But this is not an argument against such approaches, as reality is likely to be complicated. I personally would try to see if it is possible to develop a cosmological theory which is as simple as possible, and perhaps, as different as possible from our present-day conception.

      Scale-invariant dynamics (Milgrom 2009; see also
      Kroupa, Pawlowski & Milgrom 2012 ) is, I think, indicating some deeper symmetry, which might be interesting to study by talented theoretical physicists.

      I hope the above is helpful and insightful.

      (Written at the University of Vienna).

  12. David Brown Reply | Permalink

    "The falsification of the standard model of cosmology (to be more precise, of the existence of cold or warm dark matter particles) is very robust indeed." The BICEP2 results might be extremely important in this regard.
    http://arxiv.org/abs/1403.4216 "Tensor Detection Severely Constrains Axion Dark Matter", 2014, by Marsh, Grin, Hlozek, & Ferreira
    Let us assume that my quantum theory of gravity is wrong. In that case I still maintain the following conjecture:
    The main problem with string theory is that string theorists fail to realize that Milgrom is the Kepler of contemporary cosmology.
    My guess is that careful study of the cosmic microwave background radiation will rule out virtually all theories of cold or warm dark matter particles.

  13. David Brown Reply | Permalink

    "... the laws of gravitation are impervious to what the majority of established scientists think or feel." In so far as I able to judge anything I think that Milgrom, Kroupa, Pawlowski, & McGaugh have established the following: EITHER:
    (1) Newton-Einstein gravitational theory is 100% correct but appears to be slightly wrong for some unknown reason, OR
    (2) Newton-Einstein gravitational theory really is significantly wrong.
    In any case, I think that Milgrom is the Kepler of contemporary cosmology. If Linde's theory of chaotic inflation is basically correct, then I think that dark matter particles exist in the form of fermions and there must be a bizarre Fermi pairing of the dark matter fermions across matter universes and antimatter universes — something like that would necessary to make Newton-Einstein gravitational theory appear to be wrong. If Linde's theory of chaotic inflation is wrong, then I think that there are no dark matter particles whatsoever. In any case, Milgrom's acceleration law is approximately correct. I think the theory of eternal cosmological inflation is wrong because it probably implies that the space roar is due to decay of dark matter particles (which do not exist). My guess is that string theory can provide an inflation theory that cleverly explains Milgromian dynamics and implies that dark matter particles do not exist. We need to get string theorists working on this.

  14. Daniel Jencka Reply | Permalink

    Pavel,

    Sorry for taking so long to reply as I have beenn attending a conference for several days. I cannot tell you how much I apreciate your generous response. I have read the papers you cited therein and found them to be good support for your contentions. Beyond that, I admire the true scientific apporoach which your falsification exemplifies. Physicists and astrophysicists are losing their ability to critically think on their own, and I foresee that there will be a large crisis in cosmology and astrophysics due to a widespread avoidance to reappraise assumptions in light of both old and new evidence. This crsis is necessary, as Kuhn and others have said, for science to progress on some new basis.

    I also believe that there has benn a gradual over-reliance on mathematics and computer simulations, by which one can keep almost any hypothesis alive in the minds of believers. By constantly tweaking and re-interpreting the data to fit increasingly fudged models, reality dissapears in the rear-view mirror. I could say more, but anyone who understands this much already knows how serious the problem is.

    Again, I thank you for you scientific integrity, and I look forward to the eventual recognition of your falsification, and perhaps of your Milgromian dynamical approach as well.

  15. David Brown Reply | Permalink

    Daniel Jencka, writes "I also believe that there has been a gradual over-reliance on mathematics and computer simulations, by which one can keep almost any hypothesis alive in the minds of believers." Always ask, "How might the mathematical model or computer simulation be wrong?" Here are 3 of my basic ideas: (1) Experiments dictate the theory. (2) Just as a squirrel gathers acorns by hunger and instinct, the scientist should gather facts by exhaustive testing and relentless skepticism. (3) Crick's "What Mad Pursuit" is an excellent guide to science. Why have physicists ignored Milgrom for 30 years? To me the evidence looks very good for Milgrom's acceleration law. My guess is that physicists and cosmologists have gone overboard in their belief in Newton-Einstein gravitational theory. The geologists ignored Wegener for 40 or 50 years because they maintained a belief in sunken land bridges. I say theories might be good but they are never better than sound experiments and empirical findings.

  16. David Brown Reply | Permalink

    In order for string theorists to explain Milgrom's acceleration law, we need to formulate the problem in terms they can understand.
    http://arxiv.org/abs/0706.3359 "Three-Dimensional Gravity Revisited" by Edward Witten, 2007
    I think this must mean formulating the problem in terms of supersymmetry — otherwise, the string theorists won't know what to do.

  17. David Brown Reply | Permalink

    Above all else, we need to bring the problem of explaining Milgrom's acceleration law to the attention of 't Hooft. Note that in the following publication there is no reference to Milgrom's acceleration law:
    http://arxiv.org/abs/1207.3612 "Discreteness and Determinism in Superstrings" by Gerard 't Hooft, 2012
    If 't Hooft dies before we get the problem explained, then we might have to wait for a long time for someone to replace 't Hooft.

  18. ThomasM Reply | Permalink

    In the last weeks two results are reported, first the observation by the antarctic microwave telescope that the fluctuation in the microwave background give evidence for gravitational waves which are a signature of cosmic inflation, and second, an article in Nature 509, 181 (2014) on properties of galaxies reproduced by hydrodynamic simulation. It seems that reasonable agreement with the observation large an small scales is obtained, including the distribution of satellite galaxies. What does that mean for the present discussion on dark matter and a failure of the standard model of cosmology?

    Many thanks in advance for comments.

    Thomas

    • Pavel Kroupa Reply | Permalink

      Concerning the BICEP2 result, this has been shown to be questionable by
      Flauger, Hill & Spergel,
      http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1405.7351
      Citing from their abstract: "These results suggest that BICEP1 and BICEP2 data alone cannot distinguish between foregrounds and a primordial gravitational wave signal,"
      A critical discussion of this problem is available here:
      http://www.nature.com/news/no-evidence-for-or-against-gravitational-waves-1.15322?WT.mc_id=TWT_NatureNews

      It seems that the BICEPT2 claim may be a false detection due to improper correction for foreground dust.

      Concerning the CMB and its relevance for cosmology, I do not want to challenge it, but a different interpretation appears to be suggested for example by this research paper by Liu, Mertsch & Sarkar:
      http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1404.1899
      "Fingerprints of Galactic Loop I on the Cosmic Microwave Background".

      Concerning the recent work you mention in which the properties of galaxies are well reproduced in a cosmological simulation. I guess you mean this paper here:
      http://adsabs.harvard.edu/abs/2014Natur.509..177V
      by Vogelsberger et al. on "Properties of galaxies reproduced by a hydrodynamical simulation". I did study this very nice piece of work. The data library produced with this Illustris Simulation is spectacular. However, the authors understandably overrate how well the modeled galaxy population reproduces the real one. Thus, for example, the baryonic Tully-Fisher relation is not reproduced and satellite galaxies similar to those of the Milky Way are not included in this work, due to limitations on the available resolution. There are also issues with the stellar IMF and most importantly, the feedback prescriptions appear to be unphysical in that the feedback is a function of the dark matter matter halo. This is discussed here in more detail:
      http://adsabs.harvard.edu/abs/2014arXiv1406.4860K
      "Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation". In this contribution I also explicitly discuss the latest work on satellite galaxies and the attempts of the community to make the models fit with the observed anisotropies.

      But the three most recent claims that the Milky Way and/or Andromeda satellite galaxy populations can be explained within the standard model of cosmology (SMoC) as dark-matter dominated satellite galaxies, based on theoretical work using very high-resolution simulations and analytical arguments, have been found to be flawed or incomplete by this study here:
      http://adsabs.harvard.edu/abs/2014MNRAS.442.2362P
      by Pawlowski et al. (note the authors list).

      Thus the observed satellite galaxy distributions around the Milky Way and Andromeda (and meanwhile around other galxies as well) are therefore in very significant conflict with the SMoC. The crisis is deepening.

      In one of the the next postings on "The Dark Matter Crisis" we will update on the recent activities and results on satellite galaxies.

  19. David Brown Reply | Permalink

    The Milgrom-McGaugh-Kroupa-Pawlowski line of evidence rules out the ΛCDM model. There exists another line of evidence that rules out the ΛCDM model.
    "... either conventional sources of ionizing photons (galaxies and quasars) must contribute considerably more than current observational estimates or our theoretical understanding of the low-redshift universe is in need of substantial revision.”
    http://iopscience.iop.org/2041-8205/789/2/L32/article "The Photon Underproduction Crisis"
    http://arxiv.org/abs/1404.2933 "The Photon Underproduction Crisis", 10 Apr 2014

  20. David Brown Reply | Permalink

    The most important question in contemporary cosmology might be: How can the Lambda-CDM model be modified to explain MOND and the Photon Underproduction Crisis?
    http://viXra.org/pdf/1407.0113v2.pdf "Lambda-VDM Model: a Testable Modification of Lambda-CDM"
    Is there any feedback on this?

  21. David Brown Reply | Permalink

    Marcel, Pavel, & Stacy: I think that you might have overlooked an important point. I have attempted to convince the Gravity Probe B science team that their 4 ultra-precise gyroscopes functioned to within design specifications but the team rejects my argument. If the team is CORRECT then not only is the alleged Fernández-Rañada-Milgrom effect wrong but MOND is also wrong for the particular experimental data of the Gravity Probe B science team. What we need to do is to get the actual data from the Gravity Probe B experiment and demonstrate that if the 4 ultra-precise gyroscopes functioned to within design specifications, then MOND is valid for the particular experimental data of the Gravity Probe B experiment.
    http://vixra.org/abs/1207.0049 "Gravity Probe B and the Rañada-Milgrom Effect"
    99% of cosmologists are against us on MOND, but data shows that MOND is empirically valid. My wild ideas might be detrimental to the strict problem of MOND.

  22. David Brown Reply | Permalink

    I find the theories of the advocates of dark matter particles to be profoundly unsatisfactory — almost like a theory of angels and demons with vaguely specified properties.
    What percentage of dark matter particles in the observable universe have spin zero?
    What are the decay products of dark matter particles?
    From the center of the Earth to sea level, what % of the mass of the Earth is composed of dark matter particles?
    All of the advocates of dark matter particles seem to have no clear conjectures concerning the 3 preceding questions. The main idea seems to be that dark matter particles exist because MOND is wrong and MOND is wrong because Newton-Einstein gravitational theory is correct.

  23. David Brown Reply | Permalink

    Consider a geophysical argument against cold dark matter. Exotic cold dark matter particles (WIMPs) within the Earth would tend to travel to where the force of the Earth’s gravitation field is most intense. Thus these WIMPs would form a fairly thin layer resulting in a strange spike in the density of matter within the Earth’s interior. However, if there were such a spike then seismic studies of the Earth’s interior would probably already have discovered the strange spike. If 22.7 ± .014 % of the universe consists of CDM or a combination of CDM and warm DM, then why does less than 1% of the Earth’s interior consist of CDM?

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