tag:blogger.com,1999:blog-22973357.post3689243575863275560..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Echo: DDR as a Test ModelSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger22125tag:blogger.com,1999:blog-22973357.post-12004600883367566062007-03-14T13:53:00.000-04:002007-03-14T13:53:00.000-04:00I was thinking about supernovas last night and tho...I was thinking about supernovas last night and thought of what quantum gravity should predict: the quantization of the mass spectrum of black holes.<BR/><BR/>It should be an ionization spectrum turned upside down, so that Hawking Radiation occurs in steps down to some minimum threshold, after which the black hole evaporates (mind you releasing a lot of energy).<BR/><BR/>The question is then, is Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-58010521512271036322007-03-12T19:30:00.000-04:002007-03-12T19:30:00.000-04:00The different basis (both in 4-D and quantum) corr...The different basis (both in 4-D and quantum) correspond to different momentum expansions, linear, angular, etc...<BR/><BR/>It would be interesting to compute the Fourier Transform of the Schwarzschild solution on a light cone coincident with an observer.<BR/><BR/>Hehehe, kind of a little joke, every particle is its own little black hole.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-35673173043751768362007-03-12T18:32:00.000-04:002007-03-12T18:32:00.000-04:00Hi Uncle,Gravitation is empirically blind to all o...Hi Uncle,<BR/><BR/><I>Gravitation is empirically blind to all observables.</I><BR/><BR/>Gravitation is sensitive to everything that carries energy, momentum, angular momentum, that also includes field strength tensors of (possibly non-abelian) gauge charges and spin.<BR/><BR/><I> A two day calorimetry experiment could end the Equivalence Principle wholly within validated existing theory. How canSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8851846228983421682007-03-12T12:48:00.000-04:002007-03-12T12:48:00.000-04:00I know this may be hopelessly naive, but doesn't G...I know this may be hopelessly naive, but doesn't General Relativity already imply something like deformed special relativity?<BR/><BR/>It seems fairly clear that the Fourier Expansion of the space-time metric gives a metric on the momentum space.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73596115472443499192007-03-11T18:36:00.000-04:002007-03-11T18:36:00.000-04:00Hi Bee, have you read this gravity-test from Sanfo...Hi Bee, have you read this gravity-test from Sanford Uni<BR/><A HREF="http://www.sciencedaily.com/releases/2007/02/070218132127.htm" REL="nofollow">Gravity attracts Kasevich's interest</A><BR/>from "Steering Atoms Toward Better Navigation, Physicists Test Newton And Einstein Along The Way." Science Daily 23 Feb 2007.QUASAR9https://www.blogger.com/profile/00593390598251093182noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64202536905435783252007-03-11T16:42:00.000-04:002007-03-11T16:42:00.000-04:00Lorentz Invariance parity violation can be large a...Lorentz Invariance parity violation can be large and observationally consistent if confined to resolved opposite parity mass distributions. They do not naturally occur. Resolved <A HREF="http://csi.chemie.tu-darmstadt.de/ak/immel/tutorials/chirality/images/TWISTAN.jpg" REL="nofollow">twistane</A> is the most parity divergent single molecule in glass, CHI=0.72 of CHI=1 maximum. Isolated Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72452253350727498552007-03-11T14:25:00.000-04:002007-03-11T14:25:00.000-04:00Hi Christine,yes, one has to be careful. A very th...Hi Christine,<BR/><BR/>yes, one has to be careful. A very thorough investigation of the question under which circumstances experimental possibilities allow to measure a modification of the time of flight for gamma ray photons has been given in<BR/><BR/><A HREF="http://arxiv.org/abs/astro-ph/0610571" REL="nofollow">On the Problem of Detecting Quantum-Gravity Based Photon Dispersion in Gamma-Ray Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44336807250130836222007-03-11T14:21:00.000-04:002007-03-11T14:21:00.000-04:00I think it's all irrational. There could be in pri...I think it's all irrational. There could be in principle violations of Lorentz invariance although there exists absolutely no reason to think that it should be the case. But why the hell do you think that these things have anything to do with quantum gravity? What is gravitational about Lorentz violation? <BR/><BR/>Gravity is, on the contrary, the result of imposing the local Lorentz symmetry in Luboš Motlhttps://www.blogger.com/profile/17487263983247488359noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28376459294412659222007-03-11T11:58:00.000-04:002007-03-11T11:58:00.000-04:00Hi Bee,In the paper by Tsvi Piran [astro-ph/040746...Hi Bee,<BR/><BR/>In the paper by Tsvi Piran [astro-ph/0407462], the author presents some cautionary notes in using GRBs as probes to QG (see section 6). One of them is that high (~100+ MeV) and low (~100 keV) energy photons are probably not emitted simultaneously.<BR/><BR/>I'm not up-to-date with GRB literature (I was aware of this issue some time ago). Does anybody know whether this phenomenon Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61831605475829230142007-03-11T04:08:00.000-04:002007-03-11T04:08:00.000-04:00Is the case n=1 already excluded (at least morally...Is the case n=1 already excluded (at least morally) by the observation of synchrotron radiation from the Crab nebula? See astro-ph/0212190Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12888930008877674552007-03-10T22:49:00.000-05:002007-03-10T22:49:00.000-05:00Stefan:Strangelets have been thought of as possibl...<B>Stefan</B>:<A HREF="http://backreaction.blogspot.com/2006/10/does-string-theory-explain-heavy-ion.html#c116077281609747394" REL="nofollow"><I>Strangelets have been thought of as possible culprits for RHIC disaster scenarios (besides the ubiquitous black holes ;-), and as responsible for potential cosmic ray particles beyond the GZK cutoff.</I></A><BR/><BR/>While pointing to the Fly Eye and Oh PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46194134032328483392007-03-10T19:00:00.000-05:002007-03-10T19:00:00.000-05:00??Ask at the beginning of the seminar if anyone ha...??Ask at the beginning of the seminar if anyone has a hard stop??Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12359301114348021552007-03-10T17:36:00.000-05:002007-03-10T17:36:00.000-05:00Hi Moshe,well, the parameters would be tightly con...Hi Moshe,<BR/><BR/>well, the parameters would be tightly constrained. Whether or not the above scenario is affected by these constraints depends of course on the details of the so far not existent theory. I find it very possible that our universe has indeed a preferred frame, e.g. that in rest with the CMB, which breaks exact Lorentz symmetry.<BR/><BR/>(However, despite the fact that I find it Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87286709310456543952007-03-10T17:23:00.000-05:002007-03-10T17:23:00.000-05:00Hi Quasar,because ...?Because angular momentum is ...Hi Quasar,<BR/><BR/><I>because ...?</I><BR/><BR/>Because angular momentum is conserved. <BR/><BR/>I was fine with the discussion - it was very interesting. But I'm not sure how the others thought of it. <BR/><BR/>Best,<BR/><BR/>B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-15165140568415573562007-03-10T17:22:00.000-05:002007-03-10T17:22:00.000-05:00Thanks Bee, if this is true then any theory or sce...Thanks Bee, if this is true then any theory or scenario that predicts Lorentz violation at the Planck scale is already falsified...I'll take a look at the paper you mention, I am curious what are the tightest constraints, I'd be surprised if one needs to do any new experiments to dramatically constrain that scenario.<BR/><BR/>I already encountered the argument of not reducing to low energy EFT...Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-10510552540302599902007-03-10T17:12:00.000-05:002007-03-10T17:12:00.000-05:00Hi Moshe,yes, you are absolutely right. This is th...Hi Moshe,<BR/><BR/>yes, you are absolutely right. This is the reason why I prefer a scenario that does not break Lorentz invariance, and insist on that point. In the low energy effective limit all such modifications are tightly constrained, and have been thoroughly investigated, see e.g.<BR/><BR/><A HREF="http://arxiv.org/abs/hep-ph/9809521" REL="nofollow">hep-ph/9809521</A> <BR/><BR/>or search Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-32480844482354805012007-03-10T17:06:00.000-05:002007-03-10T17:06:00.000-05:00Hi Uncle,I do not know any reason or evidence why ...Hi Uncle,<BR/><BR/>I do not know any reason or evidence why QG would imply a violation of the equivalence principle. Already in standard General Relativity, a particle's spin and/or gauge charge in principle, does influence the motion of the particle, though this influence is usually negligible. This is not a violation of the equivalence principle, but a consequence of the fact that every Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-63248539122079015572007-03-10T16:48:00.000-05:002007-03-10T16:48:00.000-05:00Sorry Bee image does not allow it to be shown, so ...Sorry Bee image does not allow it to be shown, so I will try <A HREF="http://bp2.blogger.com/_cldxKGOzgeM/RfBxtIxAoTI/AAAAAAAAARk/YKld1fv3Frw/s200/blog+compton_scatter.gif" REL="nofollow">this.</A><BR/><BR/>It is an animation "borrowed" that I thought suitable.PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38339899322037858452007-03-10T16:43:00.000-05:002007-03-10T16:43:00.000-05:00Escape velocity of the photon? I'd like to contrib...<A HREF="http://eskesthai.blogspot.com/2006/11/breakthrough-propulsion-physics.html" REL="nofollow">Escape velocity of the photon</A>? I'd like to contribute but it has to be here, and not there in QGL. :( Not to smart sometimes.)<BR/><BR/> <A HREF="http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/blahol.html" REL="nofollow"><I>A black hole is an object so massive that even light cannot PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-83423340174213553402007-03-10T16:27:00.000-05:002007-03-10T16:27:00.000-05:00Hi Bee, thanks for these insights into the discuss...Hi Bee, thanks for these insights into the discussion (and the five links directly relevant at the end)<BR/>Sometimes it is a good idea to be 'flexible' and allow a talk to go on for 90 minutes. <BR/><BR/><EM>"Overall seen I find the approach interesting, though direct connections to quantum gravity seem to be weak, and more motivations than actual derivations. It is hard for me to judge on QUASAR9https://www.blogger.com/profile/00593390598251093182noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48762144615061556932007-03-10T15:34:00.000-05:002007-03-10T15:34:00.000-05:00Possibly naive question regarding Lorentz violatio...Possibly naive question regarding Lorentz violation. Suppose we have breaking of Lorentz invariance at the Planck scale, doesn't really matter how. The low energy effective field theory will now have many more allowed couplings, the coefficients of which are of determined by dimensional analysis, up to order one effects. <BR/><BR/>So, irrelevant couplings will give Planck supressed effects, whichAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-92027494244588384732007-03-10T14:58:00.000-05:002007-03-10T14:58:00.000-05:00Noncommutative geometries overall violate Lorentz ...Noncommutative geometries overall violate Lorentz Invariance with mechanisms active in chiral mass distributions' <A HREF="http://www.mazepath.com/uncleal/lajos.htm#a2" REL="nofollow">observables' divergences</A>. Do QG DDRs demand the Equivalence Principle? If not, what sources EP violations?<BR/><BR/>Arguing with equations is inferior to experimental validation or falsification. Even Anonymousnoreply@blogger.com