tag:blogger.com,1999:blog-8666091.post2321252006488594416..comments2021-07-18T19:54:06.055+02:00Comments on The Reference Frame: Adimensional gravityLuboš Motlhttp://www.blogger.com/profile/17487263983247488359noreply@blogger.comBlogger27125tag:blogger.com,1999:blog-8666091.post-29298872168642958352014-08-22T18:14:29.779+02:002014-08-22T18:14:29.779+02:00For all it's worth, this is the only scale inv...For all it's worth, this is the only scale invariance proof ever: http://arxiv.org/abs/0801.0876, http://arxiv.org/abs/physics/0608026. Strangely enough, some physicists "reinvent" my proof in/on their own terms, rather then admit it's already there and that it predates theirs. It's becoming an epidemic, it seems, since the same appears to be happening to the Multiverse proof: http://www.mynewsdesk.com/ba/pressreleases/as-big-bang-gets-downgraded-to-a-bang-the-first-scientific-proof-of-the-multiverse-claimed-975493. Hip hip, hooray! for the ongoing War of Physics, as it will produce a baby as a result of this war-rape. Still, a baby is a baby is a thy...Omerbashichnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-67368230140546161942014-08-21T00:27:27.453+02:002014-08-21T00:27:27.453+02:00LOL, I know such funny citations from Warren Siege...LOL, I know such funny citations from Warren Siegel's joke papers.<br />For example in one of them they thank God that it is Friday :-D...Dilatonnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-31162763849121534882014-08-20T21:06:23.233+02:002014-08-20T21:06:23.233+02:00No.
"Negative energies and probabilities shou...No.<br />"Negative energies and probabilities should not be considered as nonsense. They are well-defined concepts mathematically, like a negative of money." (Paul Dirac)<br />http://en.wikipedia.org/wiki/Negative_probabilityMichaelnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-3365635151035133642014-08-20T20:37:23.427+02:002014-08-20T20:37:23.427+02:00Can't the plank scale appear from no scale by ...Can't the plank scale appear from no scale by something like dimensional transmutation? Another question off the topic: dimensional transmutation appear always at a lower energy scale. Can the opposite happen? I mean you start of a theory which has no scale at low energy but it gets a scale through dimensional transmutation at higher energy?Ehabnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-51127236269043324962014-08-20T19:43:33.948+02:002014-08-20T19:43:33.948+02:00Is negative probabilities different from mathemati...Is negative probabilities different from mathematical inconsistency? John Snoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-30045949593899582222014-08-20T18:13:50.309+02:002014-08-20T18:13:50.309+02:00A very interesting paper, indeed. There is another...A very interesting paper, indeed. There is another recent paper by Hagen Kleinert that points in the same direction. He starts out with conformal gravity and gets Einstein gravity through "fluctuations" à la Coleman-Weinberg:<br /><a href="http://ejtp.com/articles/ejtpv11i30p1.pdf" rel="nofollow">Conformal Gravity with Fluctuation-Induced Einstein Behavior at Long Distances</a>.<br />He argues that one can shift the ghosts to high enough energies such that they don't matter in the same vein as the Landau pole.<br />The author makes an interesting claim at the end:<br />"The spontaneous generation of an Einstein action pro-<br />posed in this letter seems to be a much more satisfactory<br />way towards a physically acceptable quantum gravity."<br />Any opinions ?MarkusMhttp://www.markus-maute.de/trajectory/trajectory.htmlnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-57736130981874504542014-08-20T16:53:33.718+02:002014-08-20T16:53:33.718+02:00Great question. I didn't want to be too negati...Great question. I didn't want to be too negative but my answer is Not really.<br /><br /><br />The beef of the hierarchy problem really arises from the quantum fluctuations so a property of a theory before its quantum corrections are taken into account doesn't seem to affect the behavior of quantum corrections and those matter for the origin of the hierarchies.<br /><br /><br />Moreover, the hierarchy problem really means that one has to fine-tune the parameters at the high energy scale. At that scale, e.g. Planck scale, as well as at any scale where something happens, the scale invariance is violated maximally - like QCD scale invariance at the QCD scale. When the scale invariance is such a bad approximation, so is the classical description.<br /><br /><br />At the end, I have some doubts whether it makes a deeper sense to distinguish explicit and "spontaneous" violation of scale invariance, anyway.Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-27978307676750018982014-08-20T16:42:00.779+02:002014-08-20T16:42:00.779+02:00I though the minimal length/time of the Planck sca...I though the minimal length/time of the Planck scale was defined by light(C) so that in order to have something smaller in terms of time or length you need to break the barrier of light(so lengths and times smaller than the planck length make no sense/are not detectable) How do they get around this? Throw out this whole conceptual scheme? Roger M.noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-23011038239322446312014-08-20T16:07:05.472+02:002014-08-20T16:07:05.472+02:00Hello. Do you believe in Bardeen's argument th...Hello. Do you believe in Bardeen's argument that classical scale invariance solves the hierarchy problem? That argument is a motivation for agravity.andrewnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-52604220058171217912014-08-20T16:03:35.697+02:002014-08-20T16:03:35.697+02:00Thanks Lubos.Thanks Lubos.kashyap vasavadanoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-11504509935345798792014-08-20T15:51:09.459+02:002014-08-20T15:51:09.459+02:00Yes, conformal gravity has ghosts by default. Look...Yes, conformal gravity has ghosts by default. Look e.g. how Maldacena would fight them:<br /><br />http://arxiv.org/pdf/1105.5632.pdf<br /><br /><br /><br />No, (physical) conformal field theory doesn't have ghosts; they're (CFTs are) as physical theories as you may get in AdS/CFT or string theory. Conformal gravity is *not* a special case of a conformal field theory. A quantum theory of gravity isn't really a quantum field theory (in the same spacetime), so the inclusion you suggested is wrong even without the word "conformal".Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-54421218537362977642014-08-20T15:22:53.433+02:002014-08-20T15:22:53.433+02:00Hi Lubos: A question for my understanding- Does t...Hi Lubos: A question for my understanding- Does the conformal gravity theory also have the ghost problem? What about conformal field theory in general?kashyap vasavadanoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-75997778868169268112014-08-20T14:45:07.613+02:002014-08-20T14:45:07.613+02:00Ok, that answers the question I had in mind but ap...Ok, that answers the question I had in mind but apparently couldn't formulate well enough initially :) Thanks!JollyJokernoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-40800410785212578282014-08-20T14:37:00.772+02:002014-08-20T14:37:00.772+02:00Right, outside D=26, string theory had ghosts. But...Right, outside D=26, string theory had ghosts. But there was a potential for these things to decouple - become unphysical - and indeed, they do disappear in D=26.<br /><br /><br />However, the ghosts from the R^2 action don't seem to have the potential to disappear. They're as robustly present as the positive-norm states. 50:50Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-21511988993332071082014-08-20T14:14:06.331+02:002014-08-20T14:14:06.331+02:00I was thinking more in terms of how it was conside...I was thinking more in terms of how it was considered possibly inconsistent and how that was eventually resolved; not specifically about ghosts or tachyonsJollyJokernoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-13058334616261147832014-08-20T13:41:59.785+02:002014-08-20T13:41:59.785+02:00The quote linked to a satire where fascists conque...The quote linked to a satire where fascists conquered Mars solving the issue of the lack of air by beliving in the Mussolini slogan. It is a 2 layer jokeBobnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-24982441440597468552014-08-20T13:27:20.440+02:002014-08-20T13:27:20.440+02:00I don't think they are fun of Mussolini. I bel...I don't think they are fun of Mussolini. I believe that they just wanted to be provocative and attract curious readers. <br /><br />A better translation of 'me ne frego' is 'I don't care' or perhaps 'I don't give a damn'TwoBsnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-72880925119591900922014-08-20T13:03:13.674+02:002014-08-20T13:03:13.674+02:00No, 26D bosonic string theory contains no ghosts. ...No, 26D bosonic string theory contains no ghosts. You must have confused them with tachyons.<br /><br /><br />Ghosts have the wrong sign of the kinetic term partial_mu PHI partial^mu PHI. Tachyons only have the wrong sign of the potential/mass term PHI^2 / 2.Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-14798851861612391762014-08-20T13:01:28.442+02:002014-08-20T13:01:28.442+02:00Is the situation with the ghosts analogous to the ...Is the situation with the ghosts analogous to the one in string theory before it was realized it works in 26 dimensions?JollyJokernoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-88504685760239539962014-08-20T12:59:45.223+02:002014-08-20T12:59:45.223+02:00LOL, on page 23 of
http://arxiv.org/pdf/1403.4226...LOL, on page 23 of<br /><br />http://arxiv.org/pdf/1403.4226v1.pdf<br /><br /><br /><br />right before "shut up and compute" by Feynman. Are they fans of duce? ;-)Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-76539012792977449442014-08-20T12:56:26.588+02:002014-08-20T12:56:26.588+02:00Awkwardly, they had in version 1 a reference to B....Awkwardly, they had in version 1 a reference to B. Mussolini, the Italian dictator. Thank god, it is no longer there in version 2.TwoBsnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-65088680536663995422014-08-20T12:51:38.402+02:002014-08-20T12:51:38.402+02:00It is different that conformal gravity because the...It is different that conformal gravity because they detune the combination of R^2 and R_{\mu\nu}^2that would make the action conformal. In fact, I believe they have only scale invariance.TwoBsnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-9223793219645844202014-08-20T10:43:24.508+02:002014-08-20T10:43:24.508+02:00Never say never, but I would surely say that this ...Never say never, but I would surely say that this is utterly incompatible with string theory. In perturbative string theory, one really can't avoid the string scale "alpha prime" encoded in the string tension, either.<br /><br /><br />One could discuss various "alpha prime equals zero or infinity" limits of string theory. But they either produce just the low-energy effective theories beneath the string scale, or theories with an exponential tower of massless states etc.<br /><br /><br />I also think that string theory avoids ghosts not only in the final product but at every intermediate step. In the light-cone-gauge, it can be formulated so that ghosts are never a part of the spectrum. That's why I can't imagine how this whole paradigm that at least "somewhat" allows ghosts could be compatible with anything I have associated with string theory. I am using these careful or vague comments because we don't have the most general and universal definition of string theory we would like to have so the claims can't be rigorous theorems but at least the spirits seem to be completely incompatible.Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-39249048523045071882014-08-20T10:28:46.138+02:002014-08-20T10:28:46.138+02:00Can we obtain this mechanism in string theory? Tha...Can we obtain this mechanism in string theory? That would certainly take care of the ghosts and make the idea more viable and compelling in the grander scheme of things. Conversely, it would be a coffin nail if that's not possible.Michaelnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-14053835846705847882014-08-20T09:28:30.223+02:002014-08-20T09:28:30.223+02:00I just hunched that as the HEP sector of the knowl...I just hunched that as the HEP sector of the knowledge-accumulating process of Science paints itself into a corner many of its participants will become desperate and come up with all sorts of 'radically different rationals' to brake free from the the constraints imposed by the strength of string/M theory.Peter F.noreply@blogger.com