tag:blogger.com,1999:blog-22973357.post4638605266638003483..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Phenomenological Quantum GravitySabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger43125tag:blogger.com,1999:blog-22973357.post-6712078053962523352013-06-23T12:39:54.923-04:002013-06-23T12:39:54.923-04:00Hi Demian,
It was certainly kind of you to refer ...Hi Demian,<br /><br />It was certainly kind of you to refer to that as a small correction; many and my sincerest apologies are than due to his wife.<br /><br /><br />Regards,<br /><br />PhilPhil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-11970255688703372592013-06-22T20:38:50.229-04:002013-06-22T20:38:50.229-04:00"... identify the most promising experiments ..."... identify the most promising experiments to find evidence for quantum gravity." Look at Milgrom's MOND and the space roar. The space roar is supported by: (1) FIRAS & low-frequency radio data (2) ARCADE 2 & low-frequency radio data (3) ARCADE 2 & FIRAS.<br />http://asd.gsfc.nasa.gov/archive/arcade/pubs/arc2_apj_interp_2011.pdfDavid Brownhttps://www.blogger.com/profile/10537922851243581921noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34476647410015967542013-06-22T12:39:32.771-04:002013-06-22T12:39:32.771-04:00Hi Markus,
While following down that most intere...Hi Markus,<br /><br /><br />While following down that most interesting quote of Dewitt’s you posted here , I came across another of his published in <a href="http://books.google.ca/books?id=kz0_jin-9XAC&lpg=PP1&pg=PP1#v=onepage&q&f=false" rel="nofollow">a book written by his son in his memory</a>. Here he states that humans should “resist the temptation of believing that the Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57694445435009381892013-06-22T12:35:03.928-04:002013-06-22T12:35:03.928-04:00This comment has been removed by the author.Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72155529762863976392013-06-20T07:31:31.799-04:002013-06-20T07:31:31.799-04:00Hi Bee,
In the vernacular style of Richard Dawkin...Hi Bee,<br /><br />In the vernacular style of Richard Dawkins I find a Possibilian to be little more than a sexed up agnostic :-) <br /><br /><i><b>”Experience arises together with theoretical assumptions not before them, and an experience without theory is just as incomprehensible as is (allegedly) a theory without experience.”</b></i><br /><br /><br />Paul Feyerabend, “Agianst Method”, pg 151<Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24139164832974005262013-06-20T05:59:54.747-04:002013-06-20T05:59:54.747-04:00Hi Sabine,
Yes, I agree.
"In November 1949,...Hi Sabine,<br /><br />Yes, I agree.<br /><br />"In November 1949, ... I met Pauli. I was hoping to spend some time as a postdoc at the ETH, so Pauli asked me what I was working on. I said I was trying to quantize the gravitational field. For many seconds he sat silent, alternately shaking and nodding his head (a nervous habit he had, affectionately known as die<br />Paulibewegung). He MarkusMhttps://www.blogger.com/profile/03431499396962852389noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81883002610202872013-06-20T04:08:18.520-04:002013-06-20T04:08:18.520-04:00Hi Sabine
Yes, so I think we agree that renormali...Hi Sabine<br /><br />Yes, so I think we agree that renormalizability does not determine whether a theory is effective or not.<br /><br />It is neither sufficient nor necessary condition.Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-55193659662435956622013-06-20T00:10:12.824-04:002013-06-20T00:10:12.824-04:00Hi Giotis,
Yes, as I wrote, you can perturbativel...Hi Giotis,<br /><br />Yes, as I wrote, you can perturbatively ('naively') quantize it, and you get a theory, and that theory is just fine as an effective theory, but that's not what we're looking for. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86717553529045415722013-06-20T00:08:46.586-04:002013-06-20T00:08:46.586-04:00Markus,
Yes, I understand what you are saying. Wh...Markus,<br /><br />Yes, I understand what you are saying. What I mean is if you perturbatively quantize it, you don't get what you want, and everything else needs more work and we don't yet really know how it works. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33833659189627803652013-06-19T10:30:24.525-04:002013-06-19T10:30:24.525-04:00After (unfortunately from yesterday late) Wilson n...After (unfortunately from yesterday late) Wilson non re-normilizability wasn't really a problem for Gravity and for any other theory for that matter. It was understood that the perturbed QG is just an effective field theory like all QFTs and for its UV completion you need new degrees of freedom.Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89872927754529947362013-06-19T08:33:19.719-04:002013-06-19T08:33:19.719-04:00Sabine, Giotis,
sorry, I wanted to say: "It&...Sabine, Giotis,<br /><br />sorry, I wanted to say: "It's just not PERTURBATIVELY renormalizable, as are the other forces.".<br />This may have caused some confusion.<br /><br />So at least there is one theory demonstrating that renormalizability need not be the problem with gravity. But this is just a mathematical statement, if a theory matches physical reality is another thing. <brMarkusMhttps://www.blogger.com/profile/03431499396962852389noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-17584131347699562012013-06-19T07:32:41.266-04:002013-06-19T07:32:41.266-04:00Hi Phil,
Agnosticism seems to me taking the posit...Hi Phil,<br /><br />Agnosticism seems to me taking the position that we don't know, we'll probably never know, and who cares anyway. It's not an attitude that has any scientific spirit in it if you ask me, it's just a giant shoulder shrug. I definitely care what we'll find and as I said I am very convinced that we will find something, eventually. <br /><br />Maybe you'll Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19228162868417225482013-06-19T07:04:39.959-04:002013-06-19T07:04:39.959-04:00Hi Bee,
I've always favoured the agnostic app...Hi Bee,<br /><br />I've always favoured the agnostic approach whether it relates to philosophy or scientific theory, as it having hope able to keep one wanting to know more with giving due consideration to presented options, while having skepticism able to temper judgement respective of what one hopes for. Thus I find the phenomenological approach to quantum gravity more indicative of an Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12246717721200310272013-06-19T04:20:15.672-04:002013-06-19T04:20:15.672-04:00Markus, Giotis,
Yes, as you can see, I mentioned ...Markus, Giotis,<br /><br />Yes, as you can see, I mentioned asymptotically safe gravity in the above post. My point was simply this: Naively (read: perturbatively) quantized gravity breaks down at the Planck scale and isn't what we're looking for, so one has do to more than that. 'More' could be a non-trivial fixed point in the UV or it could be string theory or whatever. Loads ofSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-75423447348286913462013-06-19T02:44:34.841-04:002013-06-19T02:44:34.841-04:00Yeah, I would say that even if a theory is perturb...Yeah, I would say that even if a theory is perturbatively non-renormilizable, it could well have an UV fixed point and thus defined on all scales (i.e. fundamental). So<br />non-renormilizability is not a necessary condition for the UV completion of a theory.Giotishttps://www.blogger.com/profile/03594944884584261018noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56539999545534708712013-06-18T23:32:01.673-04:002013-06-18T23:32:01.673-04:00There is growing evidence that gravity IS renormal...There is growing evidence that gravity IS renormalizable due to the existence of a (nontrivial) UV fixed point (Asymptotic Safety). It's just not nonperturbatively renormalizable, as are the other forces.<br /><br />Best MarkusMhttps://www.blogger.com/profile/03431499396962852389noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-60763847139357769952013-06-18T17:28:09.554-04:002013-06-18T17:28:09.554-04:00The thread I was referring to is entitled "Fa...<br />The thread I was referring to is entitled "Farewell To Reality"<br /><br />Of special note is the comment on June 18, 2013 at 6:15 AM (somewhere around #45) by the author of the relevant book of the same title.<br /><br />RLO<br />Discrete Scale RelativityRobert L. Oldershawhttps://www.blogger.com/profile/15396555790655312393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20273057166327446592013-06-18T15:36:41.709-04:002013-06-18T15:36:41.709-04:00Highly relevant new post and discussion at Peter W...Highly relevant new post and discussion at Peter Woit's Not Even Wrong.Robert L. Oldershawhttps://www.blogger.com/profile/15396555790655312393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-88488294447440674172013-06-18T13:23:00.959-04:002013-06-18T13:23:00.959-04:00Freeman Dyson's 2012 Poincare Prize Lecture di...Freeman Dyson's 2012 Poincare Prize Lecture discounts single graviton detection in part for requiring "<i>a shield or a set of anti-coincidence detectors</i> [made] <i>out of some mythical material with super-high density</i>." Muon/electron mass ratio is 206.7682843. To zeroeth order orbit radius, µ,µ-H_2 would be 1/(206.7683)^3 the atomic volume of H_2 (DOI:10.1126/science.Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-68173224194225728932013-06-18T08:50:04.747-04:002013-06-18T08:50:04.747-04:00Of course these insights were and will be ignored,...Of course these insights were and will be ignored, because physical theorists are looking for ways, how to prolonge their research and how get as much grants for it as possible - not how to get their work nonsensical and ending prematurely. Quantum gravity theorists aren't an exception. We are living in era of physics driven with occupation criterions. Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-15748704148641334932013-06-18T07:20:21.986-04:002013-06-18T07:20:21.986-04:00String theory is known to be inherently fuzzy alre...String theory is known to be inherently fuzzy already, i.e. leading to vast landscape of false vacui solutions. But string theory is quantum gravity theory and it can be proven, the <a href="http://www.eurekalert.org/pub_releases/2008-10/uoo-fot100608.php" rel="nofollow">same fuzziness</a> is inherent obstacle for any other quantum gravity theory due the insintric inconsistency of postulated of Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-75435334443371474782013-06-18T06:52:35.180-04:002013-06-18T06:52:35.180-04:00A Gravitational Explanation for Quantum Mechanics:...<a href="http://arxiv.org/abs/quant-ph/9609021" rel="nofollow">A Gravitational Explanation for Quantum Mechanics</a>: There is no quantum theory of gravity. There is no graviton. Gravitational waves cannot exhibit quantum phenomena such as wave particle duality. Gravitational waves <a href="http://arxiv.org/abs/quant-ph/9706018" rel="nofollow">are not quantized</a>.Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31086484013065670862013-06-18T05:34:57.686-04:002013-06-18T05:34:57.686-04:00You see, the problem is in not yet solved renormal...You see, the problem is in not yet solved renormalization program. If one manages to renormalize the equations exactly, from the very beginning, by subtracting the counter-terms, the resulting equations will be physical, see my toy model here: arxiv.org/abs/1110.3702Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77582949946159356682013-06-18T04:37:14.121-04:002013-06-18T04:37:14.121-04:00Hi Paul,
Pheno QG models don't normally '...Hi Paul,<br /><br />Pheno QG models don't normally 'derive' Einstein's field equations, they parameterize deviations. The only two example that I know that would fit your bill might be a) Verlinde's entropic gravity. I don't know though if people have looked at the Lense Thirring effect. It seems quite unlikely because the deviations would probably primarily be relevant atSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-32170023968612120702013-06-18T04:30:55.681-04:002013-06-18T04:30:55.681-04:00Hi Giotis,
Well, I'd say renormalizability is...Hi Giotis,<br /><br />Well, I'd say renormalizability is a necessary but not a sufficient criterion as the theory can have other problems, like QED has a Landau pole. Or a theory might be renormalizable but violate unitarity. Or have some other disease that would make you doubt it's the last word. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com