tag:blogger.com,1999:blog-22973357.post2193663902378709137..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Whatever happened to AdS/CFT and the Quark Gluon Plasma? Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger49125tag:blogger.com,1999:blog-22973357.post-69963953381832714742013-09-19T01:37:41.067-04:002013-09-19T01:37:41.067-04:00John,
Please read our comment rules. I'm not ...John,<br /><br />Please read our comment rules. I'm not an ask-the-expert forum, I don't have time for this. Please use a crowd-sourced website like the physics stack exchange or physics forums for that. About the Wikipedia quote. First, while Wikipedia can supplement a textbook, it cannot replace one. Second, I'm guessing it's a verbal description of a fermion-loop correction to Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77425974767478004232013-09-18T05:30:44.492-04:002013-09-18T05:30:44.492-04:00Thanks @Andreas Karch for this very enlightening c...Thanks @Andreas Karch for this very enlightening comment that shows what is going on and why it is not reasonable to make the AdS/CFT description fit the data in domains where it has never been assumed to be relevant.<br /><br />That nicely answers the question brought up in this article why people are not trying to do this.<br /><br />Nemohttps://www.blogger.com/profile/15937686207028627202noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-17911526493870781722013-09-17T11:05:56.089-04:002013-09-17T11:05:56.089-04:00Then perhaps you could provide some helpful inform...Then perhaps you could provide some helpful information on this Sabine. I've tried to find an answer elsewhere but have been unable to do so.<br /><br />The Wikipedia <a href="http://en.wikipedia.org/wiki/Two-photon_physics" rel="nofollow">two-photon physics</a> article concerns gamma-gamma pair production, and it says this: <i>"A photon can, within the bounds of the uncertainty Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39399003012516567342013-09-17T01:17:28.389-04:002013-09-17T01:17:28.389-04:00John,
Sorry you lost me on the peas. I think you ...John,<br /><br />Sorry you lost me on the peas. I think you didn't understand my reply, maybe re-read it, we do not live in the AdS-space of AdS/CFT that is used to describe the gqp. Also, the sentence that you believe to be wrong just says that qcd, unlike qed, is non-abelian. We've now had a few exchanges on this blog and frankly it seems to me that your physics background is not the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81992598272555424812013-09-16T14:53:52.383-04:002013-09-16T14:53:52.383-04:00Qgp might not care Sabine, but I do, as does Thoma...Qgp might not care Sabine, but I do, as does Thomas Larsson and other. I've just re-read your blog and the comments, and it's kind of like <i>I agree with you and then some</i>. Especially since the AdS/CFT predicted result was so close to the straight pQCD prediction. That reminds me of "guess the weight" where you go one gram under the other guy. And then you retrofit your Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-4749595062927803172013-09-16T11:03:29.395-04:002013-09-16T11:03:29.395-04:00John,
The qgp doesn't care at all if the meas...John,<br /><br />The qgp doesn't care at all if the measured value of the cc is positive. Look, it's a model and you can use it to describe a physical system, in this case a heavy-ion collision, and the question is how well it works. Now you might question that it's a well-motivated model, which is what you seem to be saying, but that's another question. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2219817987056507802013-09-16T10:52:59.881-04:002013-09-16T10:52:59.881-04:00The difference Sabine, is that de Sitter space is ...The difference Sabine, is that de Sitter space is "a cosmological model for the physical universe" but anti-de Sitter space remains hypothetical. And in physics we have h, and electrons that come in one size only, so quantum field theory is not scale invariant. So conformal field theory is going to remain hypothetical too. And AdS/CFT correspondence is "a conjectured relationship Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31366028394075968762013-09-16T05:52:37.114-04:002013-09-16T05:52:37.114-04:00Robert,
"If we keep adding bells and whistle...Robert,<br /><br /><i>"If we keep adding bells and whistles to failing models, then we end up with increasingly bad-smelling garbage."</i><br /><br />Again, I think you're entirely misjudging the subject matter here. Heavy ion physics is not g-2. There's lots of factors going in that are presently not very well understood for not to even mention the unknown unknowns. It is very Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66023237672881419112013-09-16T05:44:53.487-04:002013-09-16T05:44:53.487-04:00Giotis,
To me it's 'physical' if it&#...Giotis,<br /><br />To me it's 'physical' if it's a description of a real world system. Now we can debate to which accuracy this has to work to be called physical, I'm not saying it's a sharp boundary, but at least presently the AdS/CFT description for the qgp doesn't quite cut it. You just seem to mean something else with 'physical.' Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8837572887012612032013-09-15T12:56:20.633-04:002013-09-15T12:56:20.633-04:00Hi Bee,
Thanks for the update on all this. So a...Hi Bee,<br /><br />Thanks for the update on all this. So as you point out all is not going so well for AdS/CFT in relation to having quark soup understood and thus a new recipe may be needed. There’s an old adage that too many cooks spoil the broth, yet in this case it seems there to be a scarcity of them. Also liked the theme music you picked for this post and yet would have to admit when I Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48767365621588453152013-09-15T11:02:21.209-04:002013-09-15T11:02:21.209-04:00It is important that our views are pointed in the ...It is important that our views are pointed in the right direction. Theoretically this implies "direction" in your model, yes?<br /><br />So understanding <a href="http://www.eskesthai.com/2013/09/exploring-matter-at-dawn-of-time.html" rel="nofollow">matter creation</a> in the early universe is an important property of any theoretical observation created to help see how that universe PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5440131012757050142013-09-15T02:46:11.985-04:002013-09-15T02:46:11.985-04:00Der denkende Mensch hat die wunderliche Eigenschaf...Der denkende Mensch hat die wunderliche Eigenschaft, dass er an die Stelle, wo das unaufgelöste Problem liegt, gern ein Phantasiebild hinfabelt, das er nicht loswerden kann.<br />- Johann Wolfgang von Goethe -MarkusMhttps://www.blogger.com/profile/03431499396962852389noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89186077554430298772013-09-14T21:24:01.559-04:002013-09-14T21:24:01.559-04:00Ist das ist nicht nur nicht richtig?
Ja das ist ni...Ist das ist nicht nur nicht richtig?<br />Ja das ist nicht nur nicht richtig!<br />Ist das nicht Herr Jürgen Würgen?<br />Ja das ist Herr Jürgen Würgen!<br /><br />Nur nicht richtig, Jürgen Würgen.<br />Oh du schone, oh du schone, oh du schone Schnitzelbank!<br /><br />Ist das ist nicht einmal falsch?<br />Ja das ist nicht einmal falsch!<br />Ist das nicht ein Dunkelbumser? <br />Ja das ist ein Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44074721877982389432013-09-14T18:16:21.679-04:002013-09-14T18:16:21.679-04:00/* dark matter, string/M-theory, quantum gravitati.../* dark matter, string/M-theory, quantum gravitation, solar axions, SUSY, extended SUSY, SUGRA, proton decay, MSSM, string/brane exotica, sparticles, leptoquarks, lazy photons, WIMPs, supersymmetry exotica, extra-dimensions, magnetic monopoles, mini-black holes, Randall-Sundrum 5-D phenomena (gravitons, K-K gluons, etc.), evidence for ADS/CFT duality, colorons, fractionally charged particles..*/<Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44902427590404091002013-09-14T13:24:00.921-04:002013-09-14T13:24:00.921-04:00List #1: Gnomes, yousie, elves, veelas, faeries, ...List #1: Gnomes, yousie, elves, veelas, faeries, imps, sprites, unicorns, leprechauns, wights, halflings, merlions, trolls, kelpies, silkies, pixies, gremlins, nymphs, dwarves, kobolds, banshees, paladins, genies, boggarts, timte, goblins, valkyries, dragons, oberons, golems, wraiths, wendigos, buraqs, nagas, undines, cecaelia...<br /><br />(Tip o' the hat to Robert Oldershaw)<br /><br />Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86333537972056015042013-09-14T10:32:51.875-04:002013-09-14T10:32:51.875-04:00"AdS/CFT is quite physical; it’s a duality be..."AdS/CFT is quite physical; it’s a duality between two physical theories, a UV complete theory of QG (i.e. String theory) in the bulk and a conformal field theory on the boundary. "<br /><br />This is a mathematical, not physical truth; and it is not a rigorous mathematical truth either (I.e., closer to the Babylonian than the Greek understanding of Pythagoras' theorem).Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53739807644355433702013-09-13T21:58:06.776-04:002013-09-13T21:58:06.776-04:00/* AdS/CFT is quite physical; it’s a duality betwe.../* AdS/CFT is quite physical; it’s a duality between two physical theories, a UV complete theory of QG (i.e. String theory) in the bulk and a conformal field theory on the boundary */<br /><br />But are these theories physical? So far the string theory has been refused with all experiments and I'm not even talking about "conformal field theory on the boundary". Such a theory is justZephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69287783654324984672013-09-13T20:21:55.469-04:002013-09-13T20:21:55.469-04:00Bee,
You say: "What you should not do is to ...<br />Bee,<br /><br />You say: "What you should not do is to take 'revision' to mean you're adding arbitrarily many unmotivated parameters, because then you can fit anything and everything."<br /><br />But if we are candid and unbiased, then we have to admit that a boat-load of ad hoc "fixes" have been added to many of the models that have dominated physics for theRobert L. Oldershawhttps://www.blogger.com/profile/15396555790655312393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90184352660534549592013-09-13T19:14:06.933-04:002013-09-13T19:14:06.933-04:00Giotis, I think you are just blind to Bee's ar...Giotis, I think you are just blind to Bee's argument here, i.e., that Ads/CFT estimates have begun to veer from the experimental results from the LHC. As Jack Nicholson would say "Son, you can't handle the truth."<br /><br />Couldn't resist. Also I read a good book recently, The Righteous Mind. It's about the ability to discern the truth and how it gets all mixed up withErichttps://www.blogger.com/profile/08213251864943443334noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48490996009350372722013-09-13T17:13:17.672-04:002013-09-13T17:13:17.672-04:00Why you are calling it a Mathematical relation? Ad...Why you are calling it a Mathematical relation? AdS/CFT is quite physical; it’s a duality between two physical theories, a UV complete theory of QG (i.e. String theory) in the bulk and a conformal field theory on the boundary. <br /><br />In my view AdS/CFT is the stringy realization of a fundamental property of Nature i.e. the Holographic principle, and has given us in a remarkable way, Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9324717779413964392013-09-13T13:05:18.620-04:002013-09-13T13:05:18.620-04:00Bee, thanks for the response. I was thinking abou...Bee, thanks for the response. I was thinking about statements I've read that the shear viscosity to entropy density ratio is universal in a class of theories, whereas other transport coefficients aren't (eg. DeWolfe et al arXiv:1304.7794 say something like this around their Eq 136-137). Are you saying that if other predictions fail, then it isn't justified to use AdS/CFT to atyyhttps://www.blogger.com/profile/12229590335815366421noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37571533495012656462013-09-13T11:07:38.348-04:002013-09-13T11:07:38.348-04:00Robert,
Models are adjusted all the time to bette...Robert,<br /><br />Models are adjusted all the time to better fit the data. You have a confusion here about what is the purpose of model building. You're trying to describe observations to extract the underlying physical concepts. If new observations don't fit the model, you go and revise it. Nothing wrong with that. What you should not do is to take 'revision' to mean you're Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1418879877716238602013-09-13T11:00:04.457-04:002013-09-13T11:00:04.457-04:00Andrew,
Not that I know of. I would be surprised ...Andrew,<br /><br />Not that I know of. I would be surprised if one could make such an argument here because there are many aspect to heavy ion collisions and only one of them is the AdS/CFT input on energy loss. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-10984498856148940252013-09-13T10:54:56.119-04:002013-09-13T10:54:56.119-04:00Zephir, I don't even have to "oppose"...Zephir, I don't even have to "oppose" you because your nonsensical babble has made yourself your own worst enemy. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7048063233776836212013-09-13T09:59:16.163-04:002013-09-13T09:59:16.163-04:00/* there some sort of universality argument why A.../* there some sort of universality argument why AdS/CFT might get the viscosity right, but not other parameters */<br /><br />IMO it is. As I told already, the reason of AdS/CFT breaking during too energetic LHC collisions is, that the QG plasma forms the nested density fluctuations, which do propagate as a rigid bodies inside of it. The actual macroscopic flow of plasma is limited to the Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.com