Tuesday, March 18, 2014

BICEP2: some winners and losers

While some theories and theorists got even bangier, others were banged in their heads

Update: on Friday, Nature will publish a rather helpful and complementary article about spring cleaning after the BICEP2 announcement.

In this blog post, I will assume that the observation of BICEP2 suggesting \(r\approx 0.20\pm 0.05\) and \(n_s\approx 0.96\pm 0.01\) is right and will eventually be confirmed by independent experiments. If the result turns out to be wrong, the whole blog post below will become irrelevant and misleading, but so will many other, more important texts and papers. That was the last time I mentioned this disclaimer in this text; I think that e.g. Matt Strassler's addition of "IF IF IF" in several colors in each sentence of his long text is a somewhat childish pose. Moreover, I think that the discovery is more likely to be right than wrong.

This new discovery is groundbreaking and has a huge impact on the health of virtually all detailed models of inflation and its audaciously proposed alternatives. Let me list some major losers and winners; I expect some true expert in inflationary model building to do a similar job "right".

The #1 loser: cyclic and ekpyrotic universes

Throughout the recent decades, Paul Steinhardt and Neil Turok were the two loudest critics of cosmic inflation. (Well, we could also include Roger Penrose, but that would bring us too far from science to science-fiction.) Most of the TRF blog posts mentioning Turok and many of those mentioning Steinhardt refer to these men's vigorous attacks against cosmic inflation.

They would be repeating that inflation doesn't solve the problems that inflation solves so beautifully and they would be proposing various cyclic and ekpyrotic (born from fire) alternatives to inflation. What is the status of this competition? Well, let them speak. Look at their 2003 paper with Justin Khoury. They wanted to show some "really bad news" for inflation. Let me quote the abstract:
We present a simple, nearly model-independent estimate that yields the predictions of the simplest inflationary and ekpyrotic/cyclic models for the spectral tilt of the primordial density inhomogeneities. Remarkably, we find that the simplest models yield an identical result: \(n_s\) is approximately \(0.95\). For inflation, the same estimate predicts a ratio of tensor to scalar contributions to the low multipoles of the microwave background anisotropy of T/S \(r=20\%\); the tensor contribution is negligible for ekpyrotic/cyclic models.
So the cyclic and ekpyrotic models are so cool because they predict negligible tensor modes. Eleven years later, an experiment measures T/S \(r=20\%\), exactly what Turok et al. assigned to inflation. The spectral index \(n_s\) predicted for inflation is consistent with the observed one within 1 sigma, too.

The agreement between the "prediction of simple inflationary models" quoted negatively in a critical paper and the observation is amazingly ironic. It reminds me of the cute 2008 story when Alain Connes calculated from some of his "noncommutative standard models" that the Higgs had to weigh \(170\GeV\). Needless to say, \(170\GeV\) was exactly the first a priori possible Higgs mass that was excluded by the Tevatron! ;-)

So I would say that cyclic and ekpyrotic cosmologies in all of their known sufficiently studied incarnations are just dead. The "cyclic/ekpyrotic vs inflation" debate could have looked like one of the religious debates that may never be settled. Some people who like to be hostile towards science would suggest that inflation isn't science, and so on. But it is a damn good science. Theories make predictions and the cyclic/ekpyrotic models predicted "negligible tensor modes" and this prediction has apparently been falsified.

Yummy. If you're keeping a list of inflation-like candidate papers to describe the Universe, you may probably throw all the papers co-authored by Steinhardt, Turok, Ovrut (sorry, Burt), and several others into the trash bin now. If you're on the board of the Perimeter Institute, you should start to think how to formulate the letter in which you fire Neil Turok from the chair of the director. Be sure he is like a sticky tick that won't resign himself; he is already "urging caution" on BICEP2 and he clearly plans to do so indefinitely. It's OK to be wrong but if you promote something to the mission of your life and you're wrong, I guess that it should have consequences.

The #1 winner: Linde's chaotic inflation

Cosmic inflation as a paradigm and its earliest co-father Alan Guth is of course the main winner but I want to be a bit more specific.

Andrei Linde's "chaotic inflation" uses the simple quadratic potential \(V=\frac 12 m^2\phi^2\) for the inflaton field. It predicts \(n\approx 0.96\), exactly the mean value measured by BICEP2, and \(r\approx 0.16\), less than one sigma below the measured central value \(r\approx 0.20\). Linde's model is remarkably simple and I tend to think that it will be viewed as the inflationary counterpart of the Standard Model's simple Higgs sector.

(The same model also makes the inflation "almost inevitably" eternal which means that the BICEP2 result strengthens the case for the multiverse – as it disfavors some possible objections against the multiverse – but of course the BICEP2 result by itself is in no way sufficient to "prove" the multiverse. And it is surely not enough to legitimize the anthropic reasoning which is yet another level.)

Liam McAllister wrote a wonderful text explaining that the inflaton field had to move by "more than the Planck mass" to achieve the inflation that produces these strong tensor modes. This is a problem because at these high changes of the scalar field, the quantum-gravity or other corrections are expected to invalidate the effective field theory. Liam has sketched some strategies to avoid this problem. Matthew Reece of Harvard wrote a post-discovery analysis and dedicated some space to a stringy "[axion] monodromy inflation" which may also circumvent the problem.

One of the other strategies to circumvent the "Lyth bound problem" was posted (today) in the first hep-ph paper that already takes the BICEP2 result into account (it was probably written when this information was "just a rumor"). Nakayama and Takahashi claim that the quadratic chaotic inflation is fine and now the well-known Higgs field may play the role of the inflaton as long as its kinetic term is modified for large values of \(h\sim \phi\). The modification is rather simple:\[

\LL = \frac 12 \zav{ 1+\xi \phi^2 } ( \partial \phi)^2 - V(\phi).

\] The unification of the Higgs and the inflaton seems economical but it is surely not among the "widely studied mainstream ideas" and it will probably avoid the mainstream, anyway, because a "new field operating at the very high, inflation/GUT scale, seems to be almost directly following" from the BICEP2 discovery. It's my guess that the Higgs=inflaton loophole should be looked at, anyway.

Using a more political attitude, the #1 winner is the Big Oil. The core of the funding for BICEP/Keck ($2.3 million) was provided by the Keck Foundation named after William Myron Keck, the founder of the Superior Oil Company that became a part of ExxonMobil. So everyone who likes the yesterday's result should praise the Big Oil! I surely do even though I haven't received a penny from them. But I did receive my share of the excitement.

Adam Falkowski mentioned another possible huge "political" loser: the Planck experiment that has so far overlooked this low-hanging Nobel-prize-winning fruit even though the experiment costs EUR 0.7 billion, over 100 times more than the BICEP experiment.

The #2 loser: the Standard Model of particle physics

I was thinking for a while which paradigm would make it to the second place, after the clear ekpyrotic/cyclic "winners among the losers". Finally, Archil Kobakhidze whom you know as the author of a paper debunking Verlinde's entropic gravity by showing that it destroys the (experimentally observed) interference of neutrons in the gravitational field (an argument I wrote independently of Archil in this blog) told us about his interesting January 2013 paper written along with Alexander Spencer-Smith.

In that paper, they were already assuming that the tensor modes would be found. Such tensor modes prove that the scale of inflation is high enough and at such high energy scales, the metastability of the Higgs boson (which may hold in the Standard Model) becomes a straight instability. Note that the anti de Sitter space (like in AdS/CFT) allows "somewhat tachyonic" particles, above the (negative) Breitenlohner-Freedman (BF) bound. On the contrary, the de Sitter space (approximately the spacetime during inflation) renders even some positive-mass particles effectively "tachyonic" and therefore inconsistent, and this is the case of the "too light" Higgs boson, too.

I tend to believe that this paper is basically correct and the Standard Model of particle physics is excluded as the right theory up to the scale of inflation by the BICEP2 data. So even though both the discovery of the Higgs boson and the B-modes seem to favor some "really simple theories", the discovery by the BICEP2 also disfavors and maybe kills the simplest theory (still) suggested by the LHC at low energies.

The #2 winner: the supersymmetric GUT scale

People have made tons of tweets about BICEP2, some of them linked to articles on this blog, and I have only retweeted a few tweets. My most favorite tweet was coming from the Twitter named Frank Wilczek, a co-father of QCD and a Nobel Prize winner. I actually liked all of his recent tweets but 15 hours ago, he wrote the following:
% To complete the synthesis, we need unification at the unification (= inflation!) scale. So: Seek SUSY, desperately! [See] Unification of Couplings
The document he linked to was his article with Savas Dimopoulos and Stuart Raby in Physics Today, October 1991. I was still just a high school student but they already outlined the most tasteful grand unified, supersymmetric theory. You may check on page 33 that the unification in the supersymmetric grand unified theory appears around the scale \(10^{16}\GeV\), and it happens to be nearly equal to the scale of inflation suggested by the BICEP2 discovery. So the unification and inflation scales are the same assuming that supersymmetry holds.

This coincidence of the unification and inflation scales has actually been discussed for decades. It seems natural from many viewpoints. There may be a big desert between the LHC scale (or a bit higher one) and the GUT scale but new fields have to arise at the GUT scale (like the GUT-breaking Higgs fields) and there's no reason why the inflaton shouldn't be a part of this GUT package. Within the string-theoretical incarnations, one also typically expects that the string scale is "just a little bit higher" than the GUT scale, but still beneath the nearby Planck scale.

(However, see Roby's comments in the comment section [he is a reader from CERN] – there is a possible problem about the "scale of inflation" as the energy density changes with time during inflation and "the" observed value isn't necessarily the most fundamental one. In particular, the mass in the quadratic coefficient is lower than the GUT scale by two orders of magnitude. I admit that he may have a point. Nevertheless, I do think that there's something nontrivial about the data which apparently make the inflation scale as high as possible a priori, a point that was also stated by Matt Strassler.)

Those things look totally consistent and one may argue that the observed tensor-to-scale ratio \(r\) was really "predicted" by SUSY GUT. So the main remaining goal is to actually find SUSY. Look for SUSY desperately. Just to be sure, the words "desperately seeking" are popular among particle physicists. Many authors wrote papers called "Desperately Seeking SUSY" (or something else) – most famously, Ginsparg and Glashow wrote "Desperately Seeking Superstrings" in 1986. All these names are parodies of a 1985 comedy-drama film "Desperately Seeking Susan".

So yes, there are reasons to think that the supersymmetry and unification haters should start to look for the backdoors to escape in a similar way as Paul Steinhardt and his cyclic colleagues.

A related justification for another "winner" or some "losers" is the comment that the scale of inflation seems to be maximized among the a priori allowed ones. So this evidence really suggests that the quantum gravity scale is close to \(10^{19}\GeV\), the traditional four-dimensional Planck scale, which therefore disfavors or rules out "large extra dimensions" (ADD) as well as "old extra dimensions" (Randall-Sundrum). Thanks to Steve Hsu for reminding me about this omission. So although these models are primarily models of particle physics, they could be viewed as major losers, too. The usual quantum gravity with the naive (very high) Planck scale seems to be a major winner.

The #3 loser: minimal SUGRA

I wasn't sure whether I would promote the 2004 paper by Barrau and Ponthieu but I wanted to add some balance, i.e. skepticism towards supersymmetry here. In that paper, they argued that if the tensor modes are found, and they have apparently been found, the cosmological constant is very high. In minimal (and perhaps not just minimal) SUGRA, the gravitino mass is linked to the cosmological constant and it comes out in the forbidden interval where the gravitino is light enough to exist and heavy enough to "hit" and destroy some successful predictions of the Big Bang Nucleosynthesis. There are several assumptions here and I am not able to quickly organize all the thoughts in my head. I hope that an expert will do it in a more rigorous blog post.

The #3 (potential) winner: string gas cosmology

Robert Brandenberger of McGill argues that the blue tilt suggested by the BICEP2 results disfavors inflation and agrees with some predictions of the string gas cosmology that has been marketed as a competitor to inflation, too. Recall that the defining "virtue" of string gas cosmology is that wrapped strings (or, in the brane gas cosmology, branes) may prevent some dimensions from expanding, and 3+1 large dimensions might be predicted by a dynamical mechanism in which the strings try to unwrap themselves (annihilate with the oppositely wound ones). Just to be sure, I would assign the inflation-less string gas cosmology at least 100 times lower priors than to the proper cosmic inflation but it is conceivable that they have a point.

Robert Brandenberger wrote some papers with Cumrun Vafa of Harvard, Ali Nayeri, and sometimes other co-authors. I was watching them as they were preparing those papers, it was fun, so even though I don't quite see how these models may replace all the desirable functions that cosmic inflation is apparently able to play, I am ready to think that they got a small positive boost by the BICEP2 data, so their paradigm has surely not been eliminated in the same way as the cyclic and ekpyrotic Universes. Robert is planning a post-BICEP2 short preprint about string gas cosmology and may contribute a guest blog, too (perhaps the same text, perhaps not).

Assorted additional losers

The graph above was posted by Adam Falkowski on Friday, when the BICEP2 was just a rumor. He told us to be ready that the graph would change. The horizontal axis shows the primordial tilt, the spectral index measured to be around \(n_s=0.96\pm 0.01\). The vertical axis shows the tensor-to-scalar ratio.

The shaded bump-like areas represent the allowed 68% and 95% regions recommended by the experiments before BICEP2. They were hills sitting on the ground because the experiments before BICEP2 were compatible with \(r=0\), the ground level. The colorful dumbbells and some of the colorful strips show predictions of various inflationary models. The smaller disk at the end of each dumbbell corresponds to the inflation with 50 \(e\)-foldings; the larger one corresponds to 60 \(e\)-foldings.

All these Planck-dominated hill-like bumps got taller (more tolerant) in the graphs of the BICEP2 collaboration because the BICEP2 collaboration had to allow for a "running spectral index", i.e. allow \(n_s\) to depend on the wave number \(k\). With this extra freedom to adjust, Planck excludes less and tolerates taller "hills". But let's use Adam's Friday graph above, anyway. The new result by BICEP2 favors a circle around \(r=0.20\pm 0.05\) whose center sits strictly above the highest bump. So without the "running spectral index", the mean value of BICEP2 would contradict the Planck exclusion limits by about 3 sigma. This looks dramatic but one must understand that the right value could very well be e.g. \(r=0.15\) which agrees with BICEP2 within one BICEP2-defined sigma; and with the Planck exclusion limits within 2 Planck sigmas. So even without the running spectral index, the contradiction wasn't really serious. (It will get serious if Planck reports more accurate data that will still suggest \(r=0\).)

So you see that the new BICEP2 circle, flying above the hills, is compatible with the \(V\sim \phi^3\) inflation (green dumbbell) and with the \(V\sim \phi^2\) quadratic inflation (the black dumbbell; Andrei Linde's chaotic inflation, already discussed as the main winner in this blog post) – and remotely with the "natural inflation" as long as it is close enough to the quadratic inflation (the upper boundary of the curved violet strip). A special point of the "power law inflation" – that seemed to contradict the Planck exclusion data – could be revived but I find it unlikely.

All the other models listed in the graph, namely \(V\sim \phi^n\) with \(n=2/3\) and \(n=1\) and the \(R^2\) inflation, seem to be at least in some conflict with the BICEP2 discovery, much like the hilltop quartic model (greenish strip). So while cosmic inflation as a paradigm has incredibly strengthened on Monday March 17th, most of the detailed models of inflation are really in trouble. Science works like that: a class of theories strengthens when most of the members of the class are exterminated. This idea may sound counter-intuitive for nations but it works for classes of theories.

The text above is written by someone who is no real expert in inflation model building but it could be interesting for some readers, anyway, and a more accurate judgment written by an expert could come soon.


  1. I thought Sean Carroll was one of the winners, since he surprised me with the first really clear and understandable (to a layman) post on Bicep2 (http://www.preposterousuniverse.com/blog/2014/03/16/gravitational-waves-in-the-cosmic-microwave-background/)

    I seem to recall one criticism of inflation being that it requires a fine-tuned starting point. I assume this, if real, can be changed to an interesting observation rather than an argument against inflation?

    Should I think of string gas cosmology as distinct from inflation or more like something that drives inflation? Looking forward to Brandenbergers post!

  2. Dear Jolly Joker, by winners and losers, I mean theories designed to explain similar bodies of data, so popular texts can't be winners.

    The statement that inflation requires a fine-tuned starting point isn't an interesting observation; it is just a lie. It is exactly the opposite of the truth because a fine-tuned starting point was needed in the Big Bang cosmology *before* inflation was added, and inflation *explains* this previously apparently fine-tuned initial state of the Big Bang phase as an inevitable consequence of the inflationary phase combined with pretty much generic, arbitrary initial conditions before inflation.

    String gas cosmology is distinct from inflation. Both of them could also co-exist but in that case, they would be relevant in different epochs of the Universe.

  3. Oh, lol, I didn't even remember it was Carroll who made the fine-tuning claim.

    Ok, apparently he's one of the losers in his day job but I remain convinced he did a good job as a blogger :)

  4. Dear Jolly Joker, it was several people like Carroll, Penrose, and a few others who promoted this completely invalid way of computing the "low probability of inflation". But even if it were 5 people of this visibility, it's still pretty painful to be one of the most visible advocates of the Flat Earth a day after Gagarin sees the Earth and it is round.

  5. Thanks for this Lubos, this is the kind of information I needed.

  6. "It reminds me of the cute 2008 story when Alain Connes calculated from some of his "noncommutative standard models" that the Higgs had to weigh 170GeV. Needless to say, 170GeV was exactly the first a priori possible Higgs mass that was excluded by the Tevatron! ;-)"

    ... which he corrected later, though: http://arxiv.org/abs/1208.1030

  7. Dear Lubos, you mention the idea that the Higgs can achieve chaotic inflation with a modified kinetic term. This was already studied in 2011 in the paper 1110.5650 ; see eq. (5) for the identical action for the Higgs. The paper takes a critical perspective, and makes the very important point that these Lagrangians can be deformed in arbitrary ways at large field values, and so the higher energy regime of inflation can't really be connected to the low energy electroweak physics.

  8. Thanks! I hopefully wasn't trying to claim that the today's paper is completely original. I would probably go back to Bezrukov and Shaposhnikov 2007 if I were trying to find the real roots of Higgs=inflaton


    and there were probably even older papers like that.

  9. LOL, the only problem with the August 2012 paper is that it is fudged up "rationalization" that was released 1 month after the Higgs was officially discovered and 8 months after all TRF readers knew that the Higgs mass was 125 GeV.

    I don't believe that there is any "deeper principle" in similar models that are ultimately equivalent to quantum field theories that could allow one to predict the values of any parameters - there's nothing like an "enhanced symmetry" etc. at the point that may be described by Connes' formalism etc. - so I won't read the 2012 paper in the same detail as the previous one.

  10. Thanks for this immensely nice article, knowing who are the losers and winners and why is what I was very curious about :-)

    Even though this article is very well explained, it made me note down many questions and models I want to learn more about, when I come to it. The more I reas about this great new discovery, the more excited I am getting :-D

    It is so nice to finally have such a non-negative, non-zero result :-)))!

    The to me most surprising thing is that these results possibly strengthen the case for the existence of a real multiverse, as explained above ....


  11. Dear Dilaton, an advantage of a sharp discovery (hopefully) like the yesterday's one is that the pile of papers you "need to read" actually shrinks so you get more time for those that are promising to be a route to progress. ;-)

  12. The above comment to Jolly Joker reminds me of the epitaph Paul Erdos suggested for himself: "Finally, I am becoming stupider no more."

  13. Hi Lubos, thanks for your response. And just to clarify: I mention the 1110.5650 paper as it was the first to mention how, in principle, one can get phi^2 inflation (chaotic) out of the higgs. While Bezrukov, Shaposhnikov have a model that is now ruled out (using huge non-minimal couplings).

    But the bigger point is, as you rightly recognize in your response, that the low energy regime and the high energy regime (landscape) are basically separate.

  14. "You may feel satisfied but you are still getting
    dumber and more ignorant."

    Well, I don't work in the field so I read these blogs for the same reason I drink beer; for fun. I didn't realize the two had the same effect though.

    The sentence I quoted is brilliant. I'll have to use it some day :)

  15. One greatly anticipates the "disproven" maths reparameterizing into acceptable envelopes (e.g., proton decay, neutrino see-saw). The past 40 years' physics much prefers safely failing at what has been established through publication to risking something new and only apparently successful by observation.

  16. Hi Světlonoši, I liked many things about Russia - and some Russians - a decade before I learned the name of Václav Klaus. I also revealed my views about the Ukrainian 2013 events before Václav Klaus did so I would urge you to respect my independence if not priority.

    Russians may have provided me with 2 weeks free sublet of a bed in a bedroom in 1988 and some other 1-dollar-sized gifts in 1992 - otherwise my experience was paid from Czech sources and my pocket, I believe.

    You can write untrue and insulting things about me or Klaus but that won't change the fact that we are right and it is sheep like you who are hopelessly brainwashed.

  17. Well, in the physic blogosphere, Lubos is the biggest winner of this news, hands down.
    Thanks a lot for all inspipring HEPH gossip, Lubos. I hope the news shows the place of all the people who made nasty attacks on you on some CS blog...

  18. Your kindness is appreciated but I am no big winner. I am just one of the thousands of little winners who are excited about the partly expected, partly surprising developments and are looking forward to more.

  19. The tweet by Wilczek is silly. (2*10^16 GeV)^4 is just the potential energy density when the inflaton was 60-efolds before the end of inflation: just one random epoch that we happen to observe today. It is not a fundamental number. Inflation with a quadratic potential wants a mass of m ≈ few x 10^13 GeV. This is the fundamental mass scale suggested by inflation, and it is 3 orders of magnitude below the SUSY-unification scale.

  20. Steve Hsu at infoproc thinks that this results shows that the Copenhagen interpretation is wrong.
    I am sure you disagree 8-)

  21. A very interesting post Lubos. I would like to understand if
    Asymptotic safe gravity ( http://arxiv.org/abs/0912.0208 ) plus slightly modified Standard Model would become a winner after all ... in the aforementioned paper SM seems to survive up to Planck scale when coupled to Gravity.

  22. LOL, up to your understatement, I do. ;-)

  23. A nice point. As a criticism, it may also be invalid if the number of efolds is exactly 60 right? Then (2e16 GeV)^4 is a fundamental number, the maximum of the potential energy density of the inflaton field. Is that right?

  24. Chalie CarbuncleMar 18, 2014, 7:11:00 PM

    Are all large extra dimension models with compactification scales above the GUT scale dead now?

  25. It is also the duty of the US to protect Ukraine. This was part of the deal when they convinced Ukraine to send her nukes back to Russia.

  26. Right, so good luck.

    Thankfully, it is no duty of the Czech Republic to join this conflict so all of us enjoy the full freedom to choose which side we prefer.

  27. Ok, casualties due to Nazis in WW2 were about 60 millions. How much "Russia killed"? What. Are. You. Talking. About?

  28. Looks like they have reached a deal:

    I have taken upon myself sufficient sacrifices in the way of
    renunciations. Here was a limit beyond which I could not go. How right this was has been proven, first by the plebiscite in the Crimea; A flaming testimony was given at that time, a declaration such as others surely had not hoped would be given.

    It was then we saw that for democracies a plebiscite becomes superfluous or even obnoxious as soon as it does not produce results democracies hoped for.

    Nevertheless this problem was solved to the happiness of the great Russian people, and now we confront the last problem that must and shall be solved.

    This is the last territorial demand I have to make in Europe, but it is a demand on which I will not yield.

    I am thankful to Mr. Obama for all his trouble and I assured him that the Russian people wants nothing but peace, but I also declared that I cannot go beyond the limits of our patience.

    I further assured him and I repeat here that if this problem is solved, there will be no further territorial problems in Europe for Russia.

    And I further assured him that at the moment that Ukraine has solved her other problems, that is, when the Ukrainians have reconciled themselves with their other minorities, the Ukrainian State no longer interests me and that, if you please, I give him the guarantee: We do not want any Ukrainians.

    I now head the procession of my people as first soldier and behind me — may the world know this — there now matches a people and a different one than that of 1989. . . .

  29. I don't understand whether your comment is serious or a joke, and in either case, what it wants to say.

    There will *always* be some conflicts and changes of borders. Believing otherwise means to live in a pinko commie utopia. When extreme or unlawful events start, it becomes much more likely for surrounding events to violate the law as well, perhaps even the law at different levels, and this elevated violations of law are only decreases once a new equilibrium is reached.

    The U.S. has demonstrably supported a violent coup in Kiev, and everyone who understands at least an iota in politics had to know that it would lead to Russia's attempts to calm the situation and to earn more than it was supposed to lose. Who couldn't predicted this simple thing is a breathtaking moron, and if such a breathtaking moron is a top politician of a democratic nation, it says something deeply unflattering about the whole nation.

  30. Well, Stalin killed 20-50 million people. But it may be useful to notice that Stalin wasn't "Russia". In fact, Stalin was Georgian. It is no coincidence that his real name was Dzhugashvilli and it is so similar to Saakashvilli! ;-)

    So it's Georgia who killed 20-50 million people, comparable to Hitler. If someone wants to use the principle of collective guilt, he should at least determine the nationality of the culprits correctly.

  31. r ≈ 0.2 means that at N ≈ 60 the inflaton vev was super-Planckian along a non-flat potential. Can somebody propose a connection with the GUT scale that goes beyond numerology?

  32. So I read a little bit of Brevick's manifesto and your blog. I feel as if you both cherry-pick information.

    Islam is not the most "violent religion" out there. In Brevick's manifesto, he frequently praises the Zoroastrians, for example. It's obvious he didn't spend much time reading about their history... Several Sassanian kings persecuted Manichaeists and had Mani killed, and they also persecuted Christians and Buddhists (i.e., Buddhism began in Persia in Parthian times and spread to China afterwards). I, at least, give Brevick credit that he acknowledge Persia and Iran as the same thing (i.e., Iran - pronounced Ērān - is from Middle Persian and the country has always been known to its own people as Iran). However, he picks and chooses data to make Muslims look more oppressive, hence his insane actions of killing people. In truth, all religions have had their periods of instability and stability, secularism and theocracy, or whatever.

    The truth is, Islam is currently in a dark age due to geopolitical reasons and the elite using dogmatic interpretations to control the masses. Many times in Persian history, such as during the Safavid dynasty or the period between ~900AD-1200AD, there was a secular and progressive form of Islam that encouraged growth. Intellectuals such as Omar Khayyam, Avicenna, Khwarizmi, Rhazes, and Sa'di were raised in such progressive Islamic societies. You cannot deny the influence Khwarizmi had on mathematics, for example.

    The ultimate problem with the Abrahamic faiths is how vague they are. You can practically form any interpretation of them and then enforce it onto people. It just happens that the contemporary interpretation of Islam in many Middle Eastern countries is oppressive. For example, Khomeini was very stupid and didn't even read figures like Sa'di or Omar Khayyam, but instead, his library was full of fundamentalist crap that had no real basis in life.

    You are very intelligent. You have very great stuff to say about string theory. I am involved in another scientific field I won't disclose. You should keep to your field without encouraging unjustified hate mongering towards a group of peoples whose history you have no grasp of. Even Zen has been utilized for war (e.g., Google WWII and Zazen).

  33. Klaus is one of the very few true heroes of post cold war Europe.

  34. Truly excellent article :D. Exactly what I was looking for! But before I start tearing out pages in my cosmology book, I have some layman questions about this article:

    1) The energy scales discussed here are measured in a co-moving volume, right?

    2) You discussed the likeliest form of the potential. From your statements can I conclude that the potential must be of the form (psi)^n (of course excluding the values of n you ruled out)?
    3) Also you said that R^2 was 'in conflict' with the data. Does this mean that f(R) cosmology is incorrect?
    4) Also I remember reading somewhere that the inflaton should be coupled to other fields so that in the past, it could have decayed into other particles. You discussed that it is unlikely that the inflaton is the Higgs since it is on an energy scale way beyond the Higgs. So are you very confident that it is a new particle?
    5) Does this experiment have any bearing whatsoever on the properties of dark matter?
    6) I haven't fully understood why you say that the GUT Supersymmetric scale is a 'winner'. Suppose it was a
    'loser' wouldn't that mean that nothing exists at those energy scales? Isn't that impossible?

  35. Yes, see p. 51 for some orientation in the inflationary jungle:
    Have fun.

  36. ow ! it is a nice information related website. I already bookmark this website & visit regularly.
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  37. LOL, a funny jungle. People love to invent names for everything here.

  38. Dear Roby, yes, I think one can propose such a connection. It's really you who is selling this as an example of numerology because you like this form.

    But one doesn't have to present it in this way. The scale of the inflation, the Hubble constant, and other parameters apparent in BICEP2 seem to take the highest values that they a priori could, right? Matt Strassler writes the same thing here:


    It seems to be the invariant statement here. So this is the sense in which one eliminates the intermediate scales, and gets as close to the Planck scale as possible.

  39. Thanks for your kind interest, TheDOC. The chance that I would make a mistake in answering your question (1) is too high. The energy scales are always the inverse of some proper times, but the precise evolution of the densities and scales during inflation is something confusing (see Roby 83's comments below) due to the rolling of the inflaton.

    (2) The allowed values of "n" are something like 2-3 here. Of course that the power law potential isn't exact in the full theory. They're just useful Ansaetze in the ballpark of realistic potentials.

    (3) I guess that you may fudge an f(R) cosmology that is close to the conventional ones, so one can't eliminate "all of them". But maybe I am wrong.

    (4) Naively, the inflaton just seems to be totally different than the Higgs but they may be related and connected and the question about their being "different" is really an ill-defined one because the point of the configuration space during inflation is - thanks to the high curvature and a different value of the inflaton - very different from the point we are occupying now. So one can't really "extrapolate" what the Higgs excitation means to the other (inflating) place of the configuration space. The configuration space is *not* a simple Cartesian product, it is a general curved space, sort of. Do you understand what I am saying? That's why you can't decide whether some excitations from "our vacuum" are "the same" as some excitations that live in a vastly different vacuum with near-Planckian curvatures and vevs. It's discussed elsewhere in these threads, I forgot exactly where, maybe under Liam's article.

    (5) I think that it doesn't. Dark matter is a relatively low-energy property of our nearly flat Universe, again not directly linked to the excitations that existed during inflation. But there are indirect connections.

    (6) I meant that the scales near the ordinary Planck scale play some important role in physics, so one can't get a full picture of physics just by using scales much lower than the SUSY-GUT scale. But as the discussion with Roby shows, I am not sure what I and Wilczek exactly meant and whether it's true. ;-)

  40. Thanks a lot for the answers. So in (4) are you saying that the 'inflaton' could possibly be the 'Higgs' (or some other particle in the present) to the entities alive in those first moments?

  41. But You ARE!
    Maybe you didnt have the nerves but I read those very nasty remarks about you, and there even was somebody, claiming to be a string theorist, who clearly called you a crackpot! Your credeility was questioned, but this news shows who is right and who is wrong.
    Of course I didn't mean you should get a nobel prize. At least for this discovery... :-)

  42. If I am not mistaken, Linde now thinks that some form of eternal cosmological inflation is more-or-less guaranteed. The argument seems to be along these lines: There is a non-zero probability that a big bang can spontaneously arise from the quantum vacuum. The only likely starting point for a new big bang is an extremely flat quantum vacuum. The only likely way for the quantum vacuum is be sufficiently flat is that the big-bang-generating quantum vacuum itself arose from a previous cosmological inflation. Is my summary of the argument wrong?

  43. These are two different questions, right? Whether you interpreted Linde's words correctly; and whether Linde's argument is correct.

  44. Hello. I am one of the authors of 1403.4132. Our idea is based on our work 1008.4457, which appeared more than one year before 1110.5650.

  45. Hello, I am one of the authors of 1403.4132. The idea is already given by ourselves in 1008.4457, which appeared more than one year before 1110.5650. The shift symmetry on a combination of scalars was proposed by myself in 1006.2801, and later studied in detail in 1008.2956 with Nakayama, under the name of the running kinetic inflation. Therefore, I am pretty sure that our paper 1403.4132 as well as 1008.4457 are the original ones.

  46. Dear Lubos,
    If the scale of inflation is 10^16 GeV, does this mean that the quantum gravity scale cannot be much lower then that (ie no large extra dimensions)?
    Does this imply that the string scale is also that high?

  47. Quantum gravity scale can never be lower than any other sensible scale defined in some way! Quantum gravity scale is, pretty much by definition, the highest possible scale in physics. Above the quantum gravity mass, one only has black holes in the spectrum.

    Yes, the string scale must be smaller than the Planck scale, like every other scale, but the data indicate that it is just "slightly" lower, as dominant approaches to string phenomenology mostly assumed.

  48. Those comments were not made by Putin, but were edited comments of another about an earlier incident that you mentioned above.

    Crimea is lost. I don't support the idea of you can have a democracy and free society until you vote for a guy who undoes the democracy, which was essentially what Yanukovych had done. Protesters got him to back down partially, and they threw him out instead.

  49. So by what logic should NATO then support the Baltic republics as they clearly have more to lose than gain?

  50. NATO is likely to support the Baltic states in order not to lose its territory; and because it's agreed in the treaty.

    But whether such a defense would actually take place is always questionable. Of course that if NATO would lose too much, e.g. create a serious risk of a destruction of the civilization, it may choose not to defend the Baltic states.

    You asked me by what logic NATO "should" defend the states but I have never made the claim that it "should". Whether one gains more than loses depends on the subjective opinions and on the situation and of course that it's wrong to "always" go to a war because of some reason, even if the reason would be "as serious as the Baltic states".

  51. Dear Dr. Takahashi, how your proposal is suposed to circunvent bounds imposed by arXiv:1301.2846 ? Do you expect that your running kinetic inflation alone would be able to stabilise the electroweak vacuum? Many thanks!

  52. Yup, unless you want me to talk about a particular SU(2) x U(1) symmetry that it was breaking - which didn't necessarily exist.

    But the Higgs oscillations are just oscillations in a particular direction in the scalar fields' configuration space, and if you move to a completely different place, the place where the inflaton has inflation-like vevs you may continuously change the direction of the Higgs oscillations so that it aligns with the inflaton.

    There's never really a global invariant way to separate scalar fields from one another. Only the whole geometry of the scalar fields' configuration space has an invariant meaning.

    I am giving a popular talk about the LHC, Higgs in an hour - BICEP was added in my slides, of course - and the directions of the Higgs oscillations in the Mexican hat etc. are being added. It's clear to me that no one will get almost anything but I still think that if a city of 170,000 chooses some dozens of people interested in particle physics, they simply have to be led beyond the superficial accounts in the mainstream media, otherwise it's a failure from the beginning.

  53. So just to clarify: can we safely say that all large extra dimension models are now dead? Lets say we have some ADD or RS model at 100 GeV, is it now dead if the BICEP data is right?

  54. Make that 100 TeV...

  55. Dear Lubos,
    I have a simple question.
    Obviously inflation ended, so why is "eternal inflation" called "eternal"?

  56. The Baltic states also have significant Russian populations, so there is certainly room for mischief.

  57. The above fake quote of Putin was actually statement from Hitler.

  58. Hi, inflation seemingly ended but it will be restarted at random places of the Universe where the inflaton fluctuates up and which start to inflate again. They create new large Universes inside the seeds and those will also produce new seeds that begin to infate, and this goes on eternally.

  59. Hello NumCracker, the bound can be evaded thanks to the running kinetic term. This is because the theory approaches a free-field theory as the Higgs field value becomes larger than a critical value around the intermediate scale. Namely, the quartic coupling stops to evolve above a certain scale.

  60. If BICEP2 is right, then I think that they're dead. In such large dimensions, gravity is weak not because the fundamental Planck scale is high but because some of the idmensions are large. But they're large relatively to the fundamental (higher-dimensional) Planck scale which means that the geometry is pretty classical and its quantum fluctuations are very small, relatively speaking, so they can't produce the large "r" i.e. strong tensor modes BICEP is apparently seeing.

    So the fundamental Planck scale must really be at least comparable to the normal GUT scale. Some dimensions may be large but not "too large" which would be needed for them to explain (most of) the Higgs hierarchy.

  61. A physics fanboy wank post here.

    In the past year:
    1) Higgs Mass;
    2) B-Modes from inflation;
    3) Some neutrino cross sections;

    In the next ten, fifteen years:
    3) Masses of a few dark matter particles;
    4) Dark energy equation of state parameter "w" to ~1% precision, and possibly dw/dz, currently a 2-sigma deviation from a cosmological constant;
    5) Possible proof of 4th "neutrino" species, currently a 2-sigma detection;
    6) Gravitational waves form LIGO;
    7) Precision tests of GR and the no-hair theorem;
    8) neutron star equation of state;
    9P Whatever the LHC teaches us when it gets to 14 TeV;

    It seems like a ***very good*** historical period to be in physics/astronomy ! Wen I was first attending physics colloquia as an undergrad, back in 2005, a major topic was the desperate search for new physics, and how theoretical physics was hard because the standard model was too perfect and matched all the data. So much for that.

  62. All of which makes your blog look good by comparison, as you've been very confidently speaking for several years that several extensions of physics beyond GR+standard model were needed, and that many theorists were on the right track and thinking effectively on these issues, in contrast to other blogs.

  63. Dear Lubos: Thanks for your rather balance post. Our paper is out and I hope you have another look at our model with a rather more positive view. Cheers.

  64. Hi Lubos, the Universe is 13.8Gy old in all this realms or, on the other hand, it has that age just in our "local" Universe? Thanks

  65. Hi Ali, good to see you here! You modestly remained silent about the URL to your new opus, so it's here:


    I will surely read it, despite being exhausted from a popular lecture (about LHC, Higgs, dark matter, inflation, plus related things) I have to a "Science Cafe" here last night, an hour got expanded to 3.5 hours and I returned at midnight.

    But your paper is compact enough so that I should read it soon.

  66. Wow Lumo,

    I wish you a good recovery from this monster-talk, and hope it was successful (it must have been, or they would not havw nailed you down for 3.5 hours ... :-D), the audience was nice and reasonable enough etc ...

    I am always jalous of people who have the opportunity to visit a talk of you ...

  67. I think it was - there was also much more laughter over there, not to mention the vastly stronger applause than one I got from a much larger audience in Science Cafe Teplice.

    The questions were very interesting, lots of people were really curious and following the stuff appropriately, so I would even claim that the more demanding presentations had their audience, a nonzero fraction of it. It was fun.

    I aired about 5 short videos with my dubbing, with slightly modified formulations of the sentences to achieve some comical effect etc., it worked well, too. They were asking about everything - inflation, big bang, how the masses are generated by the Higgs, whether expansion is allowed to be superluminal, tons of the things one may expect and some slightly unusual ones, and I think that most of them were finally explained "mostly" to their satisfaction.

    One guy got a copy of The Elegant Universe, the new edition of my translation, although I admit that I originally wanted to be compensated for it a bit LOL.

  68. What about right handed neutrinos at the LHC ?

  69. What is the most important question concerning cosmological inflation? Is Linde's theory of chaotic inflation the simplest inflation theory that is compatible with: (A) quantum field theory, (B) general relativity theory, and (C) all the known empirical findings?

  70. Hi Lubos: Thanks for the blogs on the recent monumental development. So far I have only a qualitative understanding of relationship between gravitational waves and B-mode polarization in terms of vorticity. Is there a review article (little bit more mathematical) explaining this connection with equations, metrics etc. When you recover from your exhausting schedule, are you willing to write a blog on this?

  71. Hi Kashyap, try

  72. Just to repeat: the 1110.5650 paper was the first to show that one can play these games with modified actions, but that it is arbitrary. The high energy regime of inflation is ultimately disconnected to the electroweak regime of the higgs.

  73. Lubos, Are these amazing gravity waves to be thought of as random 'quantum fluctuations' of some kind or as a more classical kind of resonance like a ringing bell? (Sorry if question is ignorant and ill-posed)

  74. "This new discovery is groundbreaking and has a huge impact on the health of all detailed models of inflation and its audaciously proposed alternatives." I suggest that the biggest winner will be Milgrom. The information I have from Kroupa is that Milgromian dynamics has been established beyond a reasonable doubt. If Kroupa is correct, then within the next few years, we will see a showdown between Newton-Einstein-compatible inflation and Milgrom-compatible inflation.

  75. --just read Matt Strassler's blog post--the concatenation of red, capitalized "IF"s reminds me of a teenage girl sitting writing her diary with a supply of colored marker pens :) -- otherwise, it was interesting, but IFIFIF makes it sound sarcastic.

  76. LOL, Matt Strassler's article here is quite "iffy" ... :-D


    I mean the article is smoothly readable, but the red "if ...if" s appearing everywhere are rather exagerated in a similar way, as pairing the term "speculative" with any BSM physics term in some of his previous articles has been ...

    Stating once and for all at the beginning what the assumptions are, as Lumo did in this TRF article, is fair and really enough. At least TRF readers do not have to be reminded of these assumptions in each paragraph again and agian, whereas about the subjects Matt Strassler often tolerates in his comment sections, I am less sure ;-)

  77. Yes, Benjamin, they were totally random quantum fluctuations, exactly the kind of vibrations that are made necessary by the uncertainty principle, like the ground-state vibrations of the harmonic oscillator.

    At some moment, they were "measured" and de facto imprinted themselves into classical waves we see today - waves that affected the density of the cosmic microwave background photons.

    While we're looking at whole "degrees" (angular ones) in the skies, i.e. billions of light years, and we see these huge waves, variations with a curl, we are really observing the effect of something that people like to imagine as a microscopic phenomenon only - quantum fluctuations.

    Isn't it amazing?

  78. Pane Motl, byl by jute ochoten přijet na jednu SŠ a udělát pro zájemce o fyziku na ní nějakou přednášku na téma strun? :)

  79. Dobrý den, děkuji za zájem. ;-) Pokud by to nebylo moc daleko. Zatím jsem tohle dělal jen asi na dvou gymnáziích v Plzni... Kde je ta Vaše škola?

  80. Ostrov nad Ohří vedle KV. :)

  81. Přitažlivé, ale přece jen trochu logisticky náročné... Omlouvám se, že jsem neřekl hned Ano...

  82. Pane Motl, bohužel jsem jen studentem a pokud teda máte zájem, nevadilo by Vám kdybych váš E-mail předal našému vyučujícímu? Svůj E-mail jsem uvedl pole. :-)

  83. Dobrý den, oceňuji Vaši aktivitu, ale jelikož to může ztroskotat jak na mé straně, takna straně vyučujícího, možná to necháme, ne? Zlomte vaz, LM

  84. Dobře, ale stejně vám děkuji. :-)

  85. Nìjtze langúagze

  86. Dear Dr. Takahashi, would it be possible to have a Higgs=Dilaton in your model? Could you please elaborate more on this (in)possibility?
    Many thanks!

  87. Hmm, that will do for me :)

  88. Hello Higgs. I disagree with you about the first part. It was clearly pointed out by us in 1008.4457 that the SM Higgs can realize the quadratic chaotic inflation with a modified kinetic term, and a more general case was studied by us in 1008.2956. (What exactly do you mean by ``these games"? Here I understand it as the Higgs chaotic inflation with the quadratic potential.)
    As a matter of fact, I agree with you about the last point. The high energy regime is almost disconnected from the EW regime. Still, it is non-trivial to show that there is at least one way to connect these two.

  89. Hi Lubos,

    A few weeks passed - what do you think now? Are you satisfied with the Inmarsat analysis re ping response times + Doppler shift?

  90. Dear Alex, I think that Inmarsat should have the capacity and know the physics, I can confirm the Doppler shift ;-) etc. but otherwise I cannot verify what they have done. It's probably correct but doesn't fully explain why they went there. The fire debilitating the pilots with a pilotless flight seems plausible to me.

  91. Thanks for this extremely interesting post, I completely forgot to read this! Congrats to Linde's chaotic inflation : )

  92. I still don't understand how authorities find a different object everyday but yet it is no part of a plane...

    My questions are:

    - why did it take so long to deploy search teams?

    - Why no mayday from pilot?

    - How can we find a soccer ball in a middle of a soccer field using google map but we cant find a plane the size of a building?

    - Or the government knows something we don't?

    Check this video i found:


  93. I have been held hostage by unknown military personal after my flight was hijacked (blindfolded). I work for IBM and I have managed to hide my cellphone in my ass during the hijack. I have been separated from the rest of the passengers and I am in a cell. My name is Philip Wood and I have been a reader of your blog for many years. I think I have been drugged as well and cannot think clearly. Maybe the photograph is helpful and you can find us now.

  94. Wasn't Erdos one of the ones who couldn't accept a Baysean analysis of the "prize behind one of three doors" quizz show? By then I guess he was already an old man?