Why Cosmology Isn’t Boring

As promised yesterday, here’s a copy of the slides I used for my talk to the ~150 participants of the collaboration meeting of the Dark Energy Survey that’s going on here this week at Sussex. The title is a reaction to a statement I heard that recent developments in cosmology, especially from Planck, have established that we live in a “Maximally Boring Universe”. I the talk I tried to explain why I don’t think the standard cosmology is at all boring. In fact, I think it’s only now that we can start to ask the really interesting questions.

At various points along the way I stopped to sample opinions…

IMG-20141022-00439

I did however notice that Josh Frieman (front left) seemed to vote in favour of all the possible options on all the questions.  I think that’s taking the multiverse idea a bit too far..

 

22 Responses to “Why Cosmology Isn’t Boring”

  1. telescoper Says:

    Vincent Icke and Peter Katgert

  2. telescoper Says:

    I believe he retired a few years ago…

  3. Anton Garrett Says:

    Slide 25 giving the various meanings of Inflation forgot the economic one.

  4. And don’t forget problems with the small-scale universe.

  5. Then there is “self-important name-dropping scold”.

    Context is key.

  6. Peter, in your slides I am surprised that you didn’t say much or deleve too much into dark matter or baryo-genesis or (origin of matter anti-matter symmetry). Are these questions resolved according to you?
    Thanks

    • telescoper Says:

      I did talk about both of these issues; they both appeared in the list of “questionable” things about the standard cosmological model.

  7. Thanks, Peter. Anyhow what I meant was let’s say there is no laboratory evidence for cold dark matter (or physics models which predict these theories) in the next 10 years, then will there be another paradigm shift in standard model of cosmology from Lambda CDM to LAMBDA + B-E condensate dark matter (or something like that).

    And on the astronomical side besides core cusp issue, due to the simple regularities in cosmic structure such as Tully-fisher relation, Renzo’s rule, dark matter dominated structures have the same asymptotic values for centripetal acceleretaions (basically something on which Stacy for eg has written a lot) bother you?

  8. Philip, I agree with you about MOND. However the observations
    I pointed and which you know about must be explained within context of standard cosmological model (or someone should
    point out why these observations are wrong be ignored).

    I don’t see any discussion or mention of these points in most cosmology talks. The only attempt I have seen is a paper about 14 years ago Mike Turner (who is a Lcdm advocate) proposed that LCDM explains milgrom’s low http://arxiv.org/abs/astro-ph/0107284
    But most cosmologists (whom I have asked) are unaware of this paper and you can check from the citations of this that there is very little follow-up to this.

    I think any hypothesis on which we built an edifice of standard cosmology should be based on evidence in a laboratory based experiment. Otherwise there is no difference between positing dark matter and positing ether.

    Also bose-einstein condensate is as well or ill-motivated from astrophysical observations as WIMP or axion(two candidates
    which are favorites of particle physicists). At any rate there are a whole zoo papers in last one year on dark matter with de-broglie wave length of order galactic scales (partly because of failure of LHC to detect anything) and I want to ask if we again are at a point
    where the standard model of cosmology is changing course from
    LCDM to LWave-like DM.

    • Same is true for positing something like WIMP or axion as a dark matter candidate

    • That’s because expansion of universe can never be verified in a laboratory based experiment and its very hard to do Sandage
      type tests to find if redshift has changed as a function of time.
      Same is true with dark energy. However, dark matter by definition is something by definition is based on fundamental physics and is a non-baryonic
      has a lifetime longer than age of universe, zero pressure .
      if you assume its a thermal relic then it has electroweak scale cross-sections. only problem is that there is so far there doesn’t seem to exist such a candidate in nature.

    • Peter, an ordinary massive neutrino is only a hot dark matter candidate and not a CDM.
      Else of course the problem would have been solved long time back and no would invest so much in underground DM experiments of look for indirect DM annihilation signals in gamma ray and positron telescopes.

      • telescoper Says:

        But it is one particle that satisfies the list of conditions you specified. Why should there not be others?

    • Peter, my point is we should have seen “some” laboratory evidence for such a particle or the theories which predict such
      a particle. We have plenty of good data from accelerators.
      10 years ago most people would have told you that
      we would know what dark matter candidate is, by now
      (esp if it has weak scale cross-sections and is a thermal relic)

      and I think that is also one reason for the rise in no of papers on “quantum degenerate dark matter” (such as BE condensate of degenerate fermion matter)
      for example :
      http://arxiv.org/abs/1409.3167
      http://arxiv.org/abs/1409.7347
      http://arxiv.org/abs/1406.6586
      and probably many more

  9. Anton Garrett Says:

    How about an “elementary particle physicist”?

  10. Philip, I am not sure whether you will find any other cosmologist agreeing to this statement from Turner’s paper which you have mentioned below

    “CDM not only predicts Milgrom’s Law (at least over a order of magnitude range in luminosity
    from 0.1L⋆ to L⋆), but also accounts for a wealth of other cosmological observations.”

  11. Sorry I meant only this part of the sentence
    “CDM not only predicts Milgrom’s Law (at least over a order of magnitude range in luminosity”
    Peter: do you agree this assertion by Turner and is this seen
    in people who do LCDM simulations with baryons?
    If so, I stand corrected. But all the people who work on LCDM, whom I have asked are not aware of this paper.

    (In fact 2 years ago I asked Rocky in a seminar about the same questions and he was dismissive of the observational pieces of evidence. If you are right, then he would have said that LCDM
    naturally predicts Milgrom’s law as shown by his colleague in 2001)

  12. Ok, but if LCDM naturally predicts milgrom’s law is an accepted fact among all cosmologists (irrespective of who wrote the first paper) then surely he (or anyone else who talks about LCDM) should mention it on the very first slide of their talks.

    • Philip, I agree that most speakers and most in audience are not
      interested in MOND. However my question is are the empirical observations which led Milgrom to propose MOND correct
      and if so are they consequence of LCDM model or a complete fluke or are they pointing to some physics we have missed in dark sector?

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