Thursday, June 19, 2014

AMS-02: no cutoff in positron fraction up to \(400^+\GeV\)

Fer137 has pointed out that the AMS-02 collaboration has published some new data a few days ago.

In contradiction with my previous sociological speculations 14 months ago, they still don't show any cutoff after 11 million electron-positron events have been taken into account.

See AMS-02's Twitter account or this NASA page for some more images and links to documents about their incomplete 2014 release (it's really this PDF file that is new) that hasn't taken the form of a paper yet.

Discovery News published a short article, too.

There's of course still some room for cutoff but AMS-02 disappointingly continues to prolong the status quo in this particular approach to detect dark matter. Recall that certain popular theories of WIMP dark matter predict that the positron fraction should be a function of energy that gradually increases but suddenly drops dramatically if the energy is increased.

With these new graphs – accurate but disappointing graphs – Sam Ting's hype about his experiment last year looks more bizarre than ever before.


  1. Well said, Lubos. Information scientists (and others) frequently fail to understand the sharp divorce of mathematics from the physical world. That’s why there is confusion regarding discreetness, which is just fine in mathematics but cannot be a part of the universe that we inhabit.

  2. Forget about trying to explain modern physics to the average person. Try explaining it to the top one percent. That is the challenge.

  3. One should not forget that TD calls the Trollking his friend and therefore naturally shares a not negligible part of the same anti-theoretical physics attitude.

    Some days ago he readily admitted that he does not care about his comment section being filled with agressive spambots instead of having nice discussions by people who are seriously interested in physics, such as the Jerusalem based physicist for example ...

    His site is simply not a serious physics blog

  4. "Language that is clear for the average person really prevents it from being precise." Layman's version of the Heisenberg Uncertainty Principle.

  5. Great post. I read this a few times in the past and I think Lubos Motl is spot on. Smolin has to basically ignore 30 years of peer-review research.

  6. If most people could easily understand, say, kwontum meckanix, then action-film producers would have to up their game since they regularly put out stuff that goes against what all average Joes then would surely know to be merely very basic classical mechanics? No?

    For example, eight-stone, beautiful buxom heroine blasts 16-stone muscular villain with pump-action shotgun firing from lovely curvy leather-clad hips on full pout. Villain is instantly blown at high speed right through tall window on fifth floor to land face-up dead spiked on the paling below. Meanwhile heroine is still holding the same pouty high-heeled pose she had when she let loose on him, not a hair out of place.

    Then comes the cutesy chest-out hair flick and posey hip thrust. Very nice. Very distracting. I guess it could even make your average Joe Soap completely forget the violation of the conservation of momentum he just witnessed, with him instead considering committing a very different kind of 'mechanical-type' violation himself at that point. :)

    Yes, that probably explains it.

  7. 1) Vacuum is trace chiral anisotropic toward matter (quarks, hadrons); 2) Noether's theorems couple exact vacuum isotropy to angular momentum conservation. Milgrom acceleration is matter trace conservation leakage. Dark matter (re Tully-Fisher relation) is curve fitting. 3) Vacuum trace chiral anisotropy is geometricallytestable: Enantiomorphic Eötvös experiments, fusion enthalpies, microwave rotation temperature, pawnbroker rotation, Galilean drop.

    Postulate-allowed observation cannot discover postulate violation. Falsifying experiments must offend physics but be consistent with all prior observation. Look.
    Are ya gonna try the obvious, or continue to pull the fantastical from betwixt yer buns?

  8. kashyap vasavadaJun 19, 2014, 6:15:00 PM

    If this excess of positrons are not coming from annihilation of dark matter, what are other believable models about their production?

  9. Lubos, regarding physics explanations for the layman your statement [One can't even explain the actual general postulates of quantum mechanics to an average physics PhD] pretty well sums it up - hopeless to the N-th power. I do like your final paragraph very much, but I think my interpretation is much more radical than yours.

    Taking consciousness as purely emergent from neuronal activity, I would say it is normal language that is “inevitably divorced” from the real world while it is only the language of mathematics that is directly relevant. I say this because I believe it is only quantitative prediction, in accord with empirical evidence, that truly provides a direct contact with reality - and so the mortar for building your pyramids. All of the words employed to “explain” things to people, posterior to an accurate quantitative theory, inevitably become fuzzy as to meaning and only become fuzzier as more words are piled on. Surely, the profusion of “QM interpretations” currently in vogue is an indicator of this. It is a very wondrous thing that mathematical quantification is even possible - the 10 decimals or so of accuracy attributed to QED is something that your average layman is utterly incapable of fully appreciating.

  10. The world desperately desires a recoilless 10-gauge shotgun loaded with 3.5" 18 pellet #00 buck shells. And maybe a big helium balloon to help lift it.

  11. PNAS 14(7) 544 (1928),
    If the foundation is rotten, the building sways.

    Phys. Rev. 105(4) 1413 (1957),
    Somebody must repair the foundation

  12. There are many levels of understanding. Especially for modern physics they form a KK tower.

  13. kashyap vasavadaJun 19, 2014, 7:33:00 PM

    I think,the main hang up is this. You can explain just about every branch of science, say chemistry, biology, geology, medical science, even psychology, using the everyday language people are used to. But the moment you try to explain modern physics in human languages (without mathematics) it come out looking crazy!! I believe that is the way it is. I expressed same idea in my guest blog!!

  14. Dear Giotis, I would agree that there are different levels at which e.g. QED may be presented. But I wouldn't call the level addressed to the average person by the word "understanding".

    It's not really an understanding. It's at most a fabricated package of propaganda that the listener (in this case the average person) is supposed to hear and perhaps memorize or repeat but he can in no way verify that what he is saying is true. He cannot verify that Feynman's contributions to QED was correct; he cannot verify it was new; he cannot verify it was important. For this reason, it is not really "understanding" in any sense. It's just some mindless package of words designed to be easy to be devoured but one really doesn't understand the topic if he hears it and repeats it!

    There is a difference between parroting something and understanding and I am confident that the slogans about QED that may be told to the average person are just completely wrong to be called "understanding".


    Feynman was a truly great teacher. He prided himself on being able to
    devise ways to explain even the most profound ideas to beginning
    students. Once, I said to him, "Dick, explain to me, so that I can
    understand it, why spin one-half particles obey Fermi-Dirac statistics."
    Sizing up his audience perfectly, Feynman said, "I'll prepare a
    freshman lecture on it." But he came back a few days later to say, "I
    couldn't do it. I couldn't reduce it to the freshman level. That means
    we don't really understand it."

  16. RobotUnicornAttackJun 19, 2014, 8:33:00 PM

    Feynman himself, of course, wrote a popular account of QED for the layman based on some lectures he gave in New Zealand,

    It is totally accessible and I don't think there is anything in it that needs to be "unlearnt" if one wishes to study the subject further. I think it's hard to argue that if you have read the book, you still have no understanding of QED whatsoever.

  17. It is excellent didactics and perhaps for the "layman" but in no way accessible to the "average person". I guess that physics-wise 90 percent bottom people have no chance to "get" the book.

  18. Yep, and what is even worse is that many people who think they have an understanding which they have not, become pompous, overreaching, and agressive, as thay think it is they are entitled to judge, criticise, condemn, etc physics they have no clue about ... :-(

  19. Hmmm, Gene, you mean
    "discreteness" --- most physicists are rather blunt, not discreet :)

  20. Einstein--"Make things as simple as possible, but not simpler". Some try to make it simpler-
    like "The Idiot's Guide to String Theory" by George Musser, or "String Theory for Dummies"
    (I haven't looked at either).
    Way to insult your readers :) :)
    Steven Gubser made an attempt with "The Little Book of String Theory"... I did read this--not bad.

  21. Physics gets hard to understand when you don't have a picture, i.e. when you can't make a movie of some process. That seems to be the case with QM. However, even in classical physics, the picture may be simple, but calculating the solution can be very difficult, e.g. planetary orbits. By the way, I think Ed Witten once wrote in a popular article that you could hold a string in a pair of tweezers, if only you and they are strong enough. I liked that vivid picture, but don't quote me on it.

  22. I bought Anthony Zee's book "Quantum Field Theory in a Nutshell" thinking it would be a reasonably easy read----great book but a hell of a lot of work to understand de novo.

  23. I read it as a kid and was very intrigued by his "stopwach analogy"; and even more surprised to learn that "adding clocks" is simply adding complex numbers, something you learn in the second year in secondary school. But you're right, I still don't understand QED. I guess I'm too average.

  24. The thing about the pyramid is, when you knock some floors off to move ahead, there exists a year or decade during which the old pyramid looks and works better. Physics in its present state is not willing to put up with any backtracking, much less 20 years worth. Hence the current stalemate.

  25. Thanks, Gordon. I have corrected it.

  26. I too have found programmers and engineers tend to have a rather simplistic view of things since they create what they program and build. They do generally fail to miss the ambiguity and messy-ness of the real world that one encounters doing science. I say this as a biologist, not a physicist, where the "messy effect" is really quite substantial.


  27. Don't ignore the subtleties, get rid of the baloney instead


  29. Exactly, Dilaton. This overreach often has scary proportions.

    But even in "innocent" examples, it's just beyond the pale. Take Woit. He clearly has no chance to understand string theory, what it actually does, what it uses to calculate what, what is adjustable, what is not adjustable, what is known, what is not known, and so on. So let's estimate that he knows 50 times less than what is needed for "understanding".

    But he writes rants and "books" authoritatively pretending that he is understanding what he is talking about. Worse yet, the readers of these rants - whose traces of "understanding" are by an additional factor of 50 smaller than the author's - are led to believe that they understand the thing themselves, and they're preaching themselves. Their understanding is some 2,500 times smaller than real understanding.

    At most, all these people are sometimes emotionally parroting some talking points that an average parrot could be taught to parrot, too. But a parrot doesn't really understand string theory or any basic of string theory that is needed to quantify its predictive value etc. Woit and his mentally defective readers are on par with the parrots, not on par with the people who actually understand the topic.

  30. Dear Tom, sensible people are not willing to abandon or replace the last 20 years or knowledge because there's no evidence that this whole knowledge is wrong and there's no seemingly or demonstrably better knowledge that could replace the old one.

  31. Bravo! Anyone who speaks of explaining physics or even some less difficult things to the average person must be REALLY REALLY CLUELESS about people.

  32. I don't restrict it to laymen; I was talking about many levels of understanding even among professional physicists.

    And what is an average person anyway? I think this is a construction of fascistic/communistic ideologies that want to treat people as cattle.

    The corner stone of Western civilization is that each person is unique with unique abilities and every man is a king of his own realm.

  33. I have it too.
    Very well written but it is a kind of book that practically presupposes that you already know QFT.
    Doing and interpreting path integrals, Wick rotations and mass spectra after 15 pages (out of a few hundreds) is indeed kind of fast :)

  34. Dear Giotis, I was talking about the average persons because that's the term that Feynman's quote has used.

    When it comes to the quantity X, the average person is the person whose X is equal to


    where X_i is the value of the i-th person and "n" is the number of people.

    Note that I need to discuss neither Nazism nor communism to define the arithmetic average! ;-)

  35. As a king of cheap demagogy I have to say that I agree with the last paragraph and this is what I've been trying to say all along.

    It is not a coincidence that in this paragraph you can't find the notion of the "average person" which is a stupid construction and does not represent a real person by any means.

    What I'm trying to say is that the expert of a field should do his best in trying to explain things to the non expert; people may or may not understand him (again there are different levels of understanding) depending on their *unique* background and their *unique* abilities.

    It is not right to put the label of the "average person" to anyone and exclude him a priori.

  36. Dear Giotis, the sentence that "an average person can't really understand QED" doesn't eliminate someone's chances to understand "a priori".

    It is a statement "a posteriori" that you may verify if you count the number of (all or average enough) people who have understood QED - after you have tried to explain QED to them.

    How I read your comment is that you want to impose some weird taboo, a ban about talking about all such questions whether the generic people or most people may understand something or not. I find such taboos or bans unacceptable, counterproductive, and intrinsically dishonest. Even if all physicists do their best to explain QED to as many people as possible, it will still be true that a vast majority of the people won't understand QED, and this result will be even more obvious if you restrict the sample to the people who are average in one way of counting it or another.

    Only if you cherry-pick the listeners in a way that makes it clear that they're not average, you will have a chance that a majority will understand e.g. Feynman's popular books about QED. What's your problem with all these obvious facts? Why do you want to emit all this stunning fog designed to pretend that the concept of the arithmetic average is a myth, or something similarly crazy that seems to follow from your PC-run-amok words?

  37. IMO we will never come closer to the mysteries of QM and GR if we dont understand how at the quantum level choices are made.
    IMO God plays dice at multiple entangled pinball machines called (CP(T) symmetric copy universes: instant entanglement at a long distance, then we don't have to worry about the box and the cat, but our Free will has become a bit smaller than we thought.

  38. Thanks for the quote, Lubos. I am proud bragging about it to my friends, although they have little idea of these scientific issues.

  39. Pulsars, are the most common hypothesis in that case.

  40. kashyap vasavadaJun 21, 2014, 1:53:00 AM

    @FER137: Thanks for the comment. As I understand pulsars are just neutron stars with intense magnetic field. Why would they distinguish between positrons and electrons? Actually neutrons, if they decay on the surface, would give electrons. Do you have a reference?

  41. I'm not a specialist. The pulsar intense magnetic field produces electron-positron pairs.

  42. Dr Christoper BremnerAug 19, 2014, 2:20:00 PM

    The positron fraction is a function of the ZPF , there will be no abrupt cut off , the average noble prize winner has an IQ of 140 , i.e. below mensa cutoff , Sam Ting is a prime example. more ass than class

  43. "... the average noble prize winner has an IQ of 140 , i.e. below mensa cutoff ..."

    Maybe, but it sounds unlikely to me. On the other hand Paul Nurse, strikes me as rather ... well, y'know ... dim! :)

    Anyway, I guess one needs to be careful about which scale is being quoted.

    Mensa International:
    "Mensa's requirement for membership is a score at or above the 98th percentile on certain standardised IQ or other approved intelligence tests, such as the Stanford-Binet Intelligence Scales. The minimum accepted score on the Stanford-Binet is 132, while for the Cattell it is 148. Most IQ tests are designed to yield a mean score of 100 with a standard deviation of 15; the 98th-percentile score under these conditions is 131."