Wednesday, March 17, 2021

Live Seminar about Dark Matter on Friday

I will give an online simiar about dark matter and modified gravity on Friday at 4pm CET, if you want to attend, the link is here:


I'm speaking in English (as you can see, half in American, half in British English, as usual), but the seminar will be live translated to Spanish, for which there's a zoom link somewhere.

28 comments:

  1. Definitely looking forward to this seminar as I'm very keenly interested in this topic. In fact, I just happened to be reading "Big Trouble in a Deep Void" over at Stacey McGaugh's Tritonstation website which proposes the idea of 11 eV, sterile neutrinos to extend MOND to Cosmological distances.

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  2. I get off work an hour before.

    Looking forward to Friday even more so.

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  3. That's 2 am in Tasmania! Is it going on YouTube?

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  4. Replies
    1. Good morning Sabine,

      it seems to me that such a blog is really very hard work.
      I think it's admirable to post something interesting every week - for over 10 years.
      I could do it too, but only for 3 weeks. And then there are the comments. It would give me a headache too. (Without Seven Evans your blog would become very dreamy....)

      I asked AstrofisicaUC about the Youtube video. Here's what they replied:
      "Dear Stefan,

      Thanks for reaching out. We will publish Sabine Hossenfelder’s recorded Golden Webinar on our YouTube channel (AstrofisicaUC) soon. Our team has been hit by the pandemic restrictions and we are doing our best to catch up with the backlog of publishing the recordings. If you have subscribed to our channel you will receive an automatic notification when the episodes become available.

      Please be a little more patient with us.

      Stay safe!

      All the best,
      Thomas Puzia"


      If allowed, I would like a blog post on super liquid.
      What do super liquid helium and super liquid dark matter have in common?

      Have a nice day
      Stefan

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  5. I generally would much rather read something than listen to it--but that was well worth the time I spent watching it. I thought it was well done, which must have required preparation and experience. It does add a bit of color/drama/je-ne-sais-quoi to see and hear a live presentation (when it goes well). A few of the questioners' comments were difficult for me to follow due to their accents, so I remain somewhat biased in favor of reading over watching--but not as much as before.

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    1. Personally, I would agree with you. But it seems to me that different communication channels work for different people and I think it's good to use all of them to reach as many people as possible.

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  6. I remember reading your paper on covariant form of Verlinde's work. It maybe don't remember it, but somehow the idea there is are different interactions for baryonic matter and photons does not strike me well.

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    1. Too ugly, huh? Can we please get over this? Some particles couple to other particles, others don't. There's no problem with this whatsoever.

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    2. It goes against the equivalence principle.

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    3. Of course not. Neutrinos don't couple to photons, but that doesn't violate the equivalence principle. I don't know what you're even talking about.

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    4. If this is all gravity, even MOND gravity, this seems to imply gravity couples differently with photons than with matter. That appears to have issues with one of the statements of the equivalence principle that gravitation acts on mass-energy independent of it's structure. At least this is a caveat that co.ea tomi d if interpret your statement here correctly.

      Suppose I had one box with matter and another with the mass eqivalent m = E/c^2 of photons. The two boxes should have the same geodesics given the same I itial conditions. One could not tell which box had hydrogen atoms and which had photons by gravitational motion alone.

      This is a question I guess I have here. Apologies if I am interpreting you wrongly.

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    5. Lawrence,

      I am afraid you are misunderstanding how superfluid dark matter works. It's a condensate which mediates an additional force that looks like gravity in that it couples to the stress-energy. However, there is nothing in this formalism that says the force needs to couple to all particles.

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    6. This still causes consternation to me. It is maybe the case, but something that "looks like gravity" is if sufficiently similar is, well ... gravity. This is by that great logic of if it looks like a duck, swims like a duck, quacks like a duck then it is a duck.

      I have had this idea kicking around, which fits into this multiverse idea, that pocket worlds may have their boundary pinch off into a sphere. I have troubles with there being a boundary, but where the data associated with that boundary exists in some form. In 2-dim that might recover something similar to MOND.

      I am not sure how that could possibly fit into Verlinde's model or your covariant extension of it. Sometimes though I wonder if the best way to solve the problem of dark matter is to not solve it, but where it might fall out of something else. Call that maybe a Zen approach.

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    7. I have not seen the seminar (hoping the video will be available soon), thus just guessing here.

      Two oppositely electrically charged bodies will exert gravity-like (attractive, 1/r^2) force on each other, while they will not interact this way with electrically non-charged bodies. And this does not violate the equivalence principle.

      Still, since different bodies see differently this additional (meant to gravity) interaction, those different bodies will undergo different trajectories (meant when everything else but electric charge will be the same for them).

      If it is the case for this dark-matter like theory, the differing paths (for different particle types) should be hopefully detectable. Would it mean that detected redshifts would differ from the inferred ones? Here (mostly) for photons coming out of centers of large matter agglomerates.

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    8. The difference is that gravitational attraction of masses puts the two masses on inertial frames. An electrostatic attraction puts them on accelerated frames.

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  7. A very intersting presentation giving a good impression of the idea perhaps widening the research on what Dark Matter could be.
    You mentioned the open question of which effects could correspond to the phase transition and how it might show up in obsservations. This reminded me of the split of measuremnts of the Hubble Constant (local/recent versus cosmological/early) in this context? Could the phase transition - assumed to have occured after sourcing of the CMB - have an impact of the Hubble constant applicable for later times?

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  8. Thank you very much. I enjoyed your presentation which was very well organized. I was glad to hear that you are continuing to pursue this research, some. I thought you were very diplomatic during the Q&A when questioners brought up some very speculative ideas.

    To answer Jim Birch's question, it was announced that an HD version would be put out on the organization's web site after YouTube's embargo period. I think they said 4 or 5 weeks.

    -Steve

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  9. Will it be uploaded to YT later? I couldn't follow it live.

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  10. Due to a scheduling conflict I only caught snippets of this towards the very end, but I very much liked what I saw. Sabine, this was a great topic and I think you did a great job of explaining both why it's interesting and how it may get even more so in the near future. Thanks!

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  11. Was looking forward to watching this live but couldn't find it. Now this video is marked "private."

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    1. It was a live stream. It automatically goes offline once finished. It will take a few days for the recording to be uploaded. I'll post a link then.

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    2. Any link for this yet? Will it be on your youtube channel?

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    3. No, not on my channel, but on this channel

      https://www.youtube.com/channel/UCyCyGFLfUZhaly2WsXJIXAQ

      As you see, it hasn't yet appeared. I'll post the link here if it goes online.

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  12. Just checked the Golden Webinars link that Sabine posted, where a recording of her seminar on Dark Matter will be presented. It's not yet up at that site, but to my delight my favorite astrophysicist, Stacy McGaugh, posted a seminar titled "Dark Matter and Gravity", which I'm currently watching.

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  13. Any news about when this will be available. I was only half way through when it disappeared.

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