tag:blogger.com,1999:blog-8666091.post7941896316839200855..comments2021-05-03T21:54:48.969+02:00Comments on The Reference Frame: Axion monodromy inflationLuboš Motlhttp://www.blogger.com/profile/17487263983247488359noreply@blogger.comBlogger21125tag:blogger.com,1999:blog-8666091.post-79998691322979272912014-03-30T17:17:54.592+02:002014-03-30T17:17:54.592+02:00@Giotis. Thanks. OK. I agree we are now at low ene...@Giotis. Thanks. OK. I agree we are now at low energy, effectively 4 Dim world. The question is whether this was true at 10^16 GeV. Does any interpretation of BICEP2 say that?kashyap vasavadanoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-74111149231096567982014-03-30T16:12:57.890+02:002014-03-30T16:12:57.890+02:00Is there a "natural" or "optimal&qu...Is there a "natural" or "optimal" way of discretizing the orbifold?David Brownnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-82280423774440316402014-03-30T12:32:07.895+02:002014-03-30T12:32:07.895+02:00Nope we are still in the low energy effective four...Nope we are still in the low energy effective four dimensional world. We don’t have to excite any KK (well for this we need to see at which scale the compactification volume moduli is stabilized) or stringy modes to produce the model. Of course in any effective filed theory we never really decoupled from the UV regime. We always have irrelevant operators in the Langrangian (produced by integrated out the heavy degrees of freedom) but they are of zero importance in low energy scales. In the large field inflationary model this is not the case anymore and we need to find a way to suppress them because they mess the potential. A symmetry is a way to do that…Giotisnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-15341813366099912222014-03-29T15:56:25.645+01:002014-03-29T15:56:25.645+01:00Perhaps I should have been clearer. It would take ...Perhaps I should have been clearer. It would take me quite some time to even remotely understand Eva's blog and Lumos' comments. I would like to understand role of a possible future theory of QG in understanding BICEP2 results. Looks like you are saying that the results imply some form of QG. is that right?kashyap vasavadanoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-52438080099037388392014-03-29T15:24:33.020+01:002014-03-29T15:24:33.020+01:00I would like to double check my layman's under...I would like to double check my layman's understanding of the developments so far with experts.Please tell me if this is right or wrong. My feeling is that if BICEP2 is correct, it proves that one can get by with classical GR and QFT until 10^16 GeV. So one would need ST to take us from there to Planck energy. Also I have read that model of cosmic strings has been eliminated. Is this right or misinformation?kashyap vasavadanoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-5445603691977967602014-03-29T13:35:15.867+01:002014-03-29T13:35:15.867+01:00Eva's answer may be different. ;-)
But my an...Eva's answer may be different. ;-)<br /><br /><br />But my answer is No, there is no contradiction. Inflation may be viewed as another part of the standard physics obeying the old-fashioned rules including naturalness - the desire to avoid fine-tuning.<br /><br /><br />Eternal inflation is also sometimes used as a starting point for the anthropic reasoning that allows or encourages one to abandon the usual concepts of naturalness altogether but the anthropic reasoning in no way "follows" from the mechanisms of inflation themselves - not even when the multiverse is created - so there's no demonstrable contradiction between naturalness demanded from some mechanisms in inflation on one side; and the speculative ability of inflation to justify the abolition of the naturalness reasoning.<br /><br /><br />Another question is what the people who actually abandon naturalness - because of anthropic considerations - do with the apparent and sometimes "damn too obvious" fine-tuning that may be present in some models of inflation. I think that they don't know because there's really no convincing specific enough "realization" of the anthropic reasoning, at least not one that would produce some correct predictions and no wrong predictions. At the end, any consistent picture must have "some" notion of naturalness. It may be "biased" in favor of the creation of humans but it must exist. It should also exist within a well-defined dynamical theory, like string theory, but string theory itself doesn't seem to directly imply any anthropically biased rules of naturalness.Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-50901314896662243122014-03-29T12:18:23.838+01:002014-03-29T12:18:23.838+01:00Something that popped into my mind:
Is there a lo...Something that popped into my mind:<br /><br />Is there a logical contradiction in trying to enforce naturalness in an inflationary model taking into account that future eternal inflation supports the multiverse idea which is often used as a justification of fine tuning?Giotisnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-61662875037428627862014-03-29T02:11:16.307+01:002014-03-29T02:11:16.307+01:00It looks like string theory is finally being teste...It looks like string theory is finally being tested. From the little I can gather, certain space time configurations of the hidden dimensions are being whittled down to incorporate simple inflation. I wonder who the negative, small minded trolls are spinning this who think string theory is bogus because it was 30 years ahead of it's time.Physics Junkienoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-89725229977276561902014-03-28T20:32:15.224+01:002014-03-28T20:32:15.224+01:00http://vkontakte-anonym.blogspot.com/http://vkontakte-anonym.blogspot.com/Алексей Яковецnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-86617692229620359782014-03-28T18:22:57.959+01:002014-03-28T18:22:57.959+01:00Thanks for this detailed analysis and your effort....Thanks for this detailed analysis and your effort.<br /><br /><br />What about Heterotic M-theory inflation? Nobody mentions these models and I remember that they produce detectable gravitational waves. <br /><br /><br />Also can you have the required symmetry in Heterotic M-theory?Giotisnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-9368148927081304472014-03-28T17:33:42.325+01:002014-03-28T17:33:42.325+01:00Like your summary, Eva, and the mechanism of study...Like your summary, Eva, and the mechanism of studying the axion potentials with higher rank pform potentials coupled via Chern Simons terms, and resulting axion/inflaton potentials. The pform gauge-Yang Mills symmetries are a beautiful constraint which arises directly from string/M theory. It would be nice if more complete phenomenology could begin, as suggested for example in Ibanez et al's recent paper, so that the supersymmetry breaking scale and inflation are considered simultaneously, and a more realistic and complete brane configuration/compactification be considered. Yes, I know that is asking for a lot, but the recent impetus gives us hope we can begin on that stage, right? Nicely written!Shyamoli Plassmannnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-47564275661932076092014-03-28T17:15:43.948+01:002014-03-28T17:15:43.948+01:00By "confined" I mean that nature is infi...By "confined" I mean that nature is infinite and digital. I conjecture that there are 3 basic possibilities for nature: (1) infinite and non-digital, (2) infinite and digital, or (3) finite and digital. By "confined" I mean that each string vibration has a digital representation with respect to the Leech lattice. Is there a publication in which the string landscape is conjectured to be infinite and digital?David Brownnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-57532834853995353902014-03-28T17:12:58.095+01:002014-03-28T17:12:58.095+01:00You cannot get by without a trace-broken symmetry....You cannot get by without a trace-broken symmetry. You have one before your eyes. Test for it locally: 90 days in existing bench top apparatus.<br /><br />BICEP2 sees vortices. One cannot go behind them. They are chiral (re chiral relativistic beta-rays that slow to mere helicity). Physics postulates achiral isotropic space, then suffers unending parity violations, symmetry breakings, chiral anomalies, Chern-Simons repair of Einstein-Hilbert action, toward fermionic matter (hadrons, quarks). Trace chiral anisotropic space heals quantum gravitation, SUSY, and dark matter. <br /><br />Visually and chemically identical single crystal test masses in enantiomorphic space groups, opposite shoes in left-footed vacuum, free fall along non-identical minimum action paths. Left-handed versus right-handed alpha-quartz violates the Equivalence Principle. A geometric Eötvös experiment contrasts paired 20 gram test mass loadings, 6.68×10^22 pairs of opposite shoes, pairs of 9-atom enantiomorphic unit cells. Look.Uncle Alhttp://www.mazepath.com/uncleal/qz4.htmnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-15160466949626032402014-03-28T17:07:06.831+01:002014-03-28T17:07:06.831+01:00A very nice, clear discussion from the layman'...A very nice, clear discussion from the layman's point of view. And well written -- that aspect I can judge with some assurance. thanks,lukeleanoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-3025444036692928982014-03-28T16:48:57.837+01:002014-03-28T16:48:57.837+01:00Yes thank you for your contributions to the world ...Yes thank you for your contributions to the world mind on string theory together with Lubos, John Preskill(on inflaton rolls) and Liam. You all have become a formidable force to the advancement of information as we lay people are moved forward into the realities of these frameworks and the theoretics gained from the scientific views.PlatoHagelhttp://www.eskesthai.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-17140456262711821172014-03-28T15:00:29.465+01:002014-03-28T15:00:29.465+01:00By the way, Dilaton (and others), if you had time,...By the way, Dilaton (and others), if you had time, there is a cool Harvard colloquium from this Tuesday now posted:<br /><br /><br />http://media.physics.harvard.edu/video/?id=SPECIALCOLLOQ_KOVAC-GUTH_032514<br /><br /><br /><br />Melissa Franklin introduces it, the same colloquium I would attend every other week or so for six years. ;-) Willie Soon sent me the link.<br /><br /><br />It's two hours - John Kováč and Alan Guth...Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-15407602422338073932014-03-28T14:48:14.577+01:002014-03-28T14:48:14.577+01:00David, LOL, Eva may give you a better answer but: ...David, LOL, Eva may give you a better answer but: did you invent the concept of "string theory on the Leech lattice" yourself and independently? <br /><br />It would be impressive because the answer is a resounding Yes. String theory on the Leech lattice, more precisely on the 24-torus R^24/Lambda where Lambda is the Leech lattice, exists and is very important. <br /><br />First, it is the string theory that explains the monstrous moonshine:<br /><br />http://inspirehep.net/search?ln=en&ln=en&p=find+a+dixon+and+title+beast&of=hb&action_search=Search&sf=&so=d&rm=&rg=25&sc=0<br /><br />http://ccdb5fs.kek.jp/cgi-bin/img/allpdf?198806247<br /><br />More recently, Witten provided evidence that a related (in some sense the same) string theory on the Leech lattice is the holographic dual of pure gravity in AdS3, the simplest gravitational theory in 3D hyperboloid space.<br /><br />http://motls.blogspot.com/search?q=Leech+monstrous&m=1&by-date=true<br /><br /><br /><br />Start with the oldest blog posts if you want them.Luboš Motlhttp://motls.blogspot.com/noreply@blogger.comtag:blogger.com,1999:blog-8666091.post-47863977810358278412014-03-28T14:05:50.048+01:002014-03-28T14:05:50.048+01:00"... approach this with due modesty." Le..."... approach this with due modesty." Let us assume that my quantum theory of gravity is complete rubbish. Are there any publications in refereed physics journals that consider the possibility that string vibrations are confined to the Leech lattice (or several copies of the Leech lattice)?David Brownnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-81081423204509934382014-03-28T13:27:20.002+01:002014-03-28T13:27:20.002+01:00Oh yeah, looking forward to read this after work a...Oh yeah, looking forward to read this after work and see what I can get out of it :-)<br /><br />Cheers !Dilatonnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-796902917836172562014-03-28T08:49:22.755+01:002014-03-28T08:49:22.755+01:00Hi Lubos, Thanks to you for the invitation and th...Hi Lubos, Thanks to you for the invitation and the discussion. <br /><br />I like the analogy to long strings in matrix theory and black holes, another example of how string theory exhibits intricate structures required by physics (in that case thought experiments). I may be biased, but I don't regard these structures as contrived (as you say they are discovered not invented), although I completely agree that the theory adds a lot of degrees of freedom and certain complications, including moduli stabilization. I think there is a lot more to do conceptually to understand more about how even those complications might be relevant for e.g. de Sitter entropy, which might make their role more clear. In fact almost every inflationary mechanism I have stumbled upon was discovered serendipitously in the process of trying to address that problem. <br /><br />The empirical question you ask is a of course a very reasonable and important one. It will be very interesting to see whether the data ends up centering on the m^2 phi^2 predictions (which may appear as a special case in string theory but doesn't look preferred). There is still some chance of much more detailed signatures at the level of structure in the power spectrum (e.g. oscillations), or particular shapes of non-Gaussianities, which could in principle provide smoking guns for certain mechanisms. But it's hard to assess the probability of that happening -- I was much more confident that B modes would be detected than I am about any of the other interesting signatures, because they seem more model-dependent, although I think they remain very interesting possibilities. Another wonderful thing about the BICEP result is that with relatively large r, some additional features could become observationally accessible with forthcoming experiments, such as its tilt and even some constraints on its non-Gaussianity. <br /><br />Finally, perhaps we should approach this with due modesty, since after all the level of precision we now have in cosmology seemed like a pipe dream 30 years ago when inflationary theory began. I hope/expect that people will find some new ways to probe this physics that we have not anticipated.Eva Silversteinnoreply@blogger.comtag:blogger.com,1999:blog-8666091.post-90192548931223044802014-03-28T07:53:57.322+01:002014-03-28T07:53:57.322+01:00Dear Eva, thank you for this wonderful guest post....Dear Eva, thank you for this wonderful guest post. It's a good observation that theorists are better prepared than for the nonzero C.C. - to some extent, the tension between the positive C.C. and different theoretical expectations caused quite some years of frustration, I think.<br /><br /><br />Of course, I am the easiest to be convinced that the monodromy mechanism is natural and, let's say it, beautiful. The way how the inflaton range is effectively extended by a large integer factor is fully analogous to the long strings in matrix string theory which may also be called "the fundamental way" how string theory compresses information about long objects. It's a loophole that shows that the "no-go theorems" for the large-field inflation in string theory must be just order-of-magnitude estimates of a sort.<br /><br /><br />(This point should also have an analogy in the related "weak gravity conjecture" which is mathematically similar to the inequalities banning simple large-field inflation in string theory. As far as I could say, we never found "the" right universal inequality expressing the weak gravity conjecture for a general vacuum with a general spectrum, and things like complicated monodromies or otherwise complicated configuration spaces might potentially render the weak gravity inequality vacuous. Of course, the near-extremal black holes should still be able to radiate away, for QG consistency, but there might be a monodromy-like trick to guarantee this condition without constraining the spectrum too much, too.)<br /><br /><br />I obviously think that something like that - monodromy inflation, N-flation etc. - is necessary to avoid the genuine problems with the Lyth bound etc. On the other hand, from a practical perspective, even people who are rather careful could suggest that the string-theory modelling of these things "adds" a lot of stuff that isn't bringing insights practically. It seems like Nature tolerates one's being a sloppy field theorist who just thinks that a large-field inflation is OK, the huge QG corrections may be ignored or assumed to do the right thing, one inflaton is enough, and so on. In string theory, one is much less sloppy so she views these things as problems, and to solve them, she has to consider many axions or complicated monodromies etc. which, from a bottom-up field theorist's viewpoint, make the thing more complicated.<br /><br /><br />These are two (top-down, bottom-up) increasingly different ways of thinking which descriptions are a priori more natural, simpler, and more likely. I think that you're on the same side as how I feel. But do you think there is a chance that the features of the "careful top-down approach" and string theory in particular will be experimentally shown "necessary" and that the "sloppy bottom-up" field-theoretical based approach will be identified as insufficient - or at least, more contrived even from the sloppy field theorist's viewpoint?Luboš Motlhttp://motls.blogspot.com/noreply@blogger.com