Various and Sundry

A few links for your weekend reading:

  • If you just can’t get enough of the Multiverse, Inference has commentary on Max Tegmark from Daniel Kleitman and Sheldon Glashow.
  • Coverage of the important topic of blackboards is to be found here. To those ill-informed sorts who think that blackboards are the past, whiteboards or some other technology the future, I’ll point out the following. When I came to Columbia back in 1989, there was a recently installed modest-sized whiteboard in the math department common room. Everyone hated it, and after many years it was replaced by a similar-sized blackboard. Last year, in a renovation of the lounge, that blackboard was replaced by a better one, and one whole wall of the room was replaced by a floor-to-ceiling blackboard. A year or so ago, a newly renovated Theory Center was unveiled here in the Physics department: floor-to-ceiling, wall-to-wall blackboards. That’s the future, the whiteboard is the past.
  • The latest CERN Courier has a long article by Hermann Nicolai, mostly about quantum gravity. Nicolai makes the following interesting comments about supersymmetry and unification:

    To the great disappointment of many, experimental searches at the LHC so far have found no evidence for the superpartners predicted by N = 1 supersymmetry. However, there is no reason to give up on the idea of supersymmetry as such, since the refutation of low-energy supersymmetry would only mean that the most simple-minded way of implementing this idea does not work. Indeed, the initial excitement about supersymmetry in the 1970s had nothing to do with the hierarchy problem, but rather because it offered a way to circumvent the so-called Coleman–Mandula no-go theorem – a beautiful possibility that is precisely not realised by the models currently being tested at the LHC.

    In fact, the reduplication of internal quantum numbers predicted by N = 1 supersymmetry is avoided in theories with extended (N > 1) supersymmetry. Among all supersymmetric theories, maximal N = 8 supergravity stands out as the most symmetric. Its status with regard to perturbative finiteness is still unclear, although recent work has revealed amazing and unexpected cancellations. However, there is one very strange agreement between this theory and observation, first emphasised by Gell-Mann: the number of spin-1/2 fermions remaining after complete breaking of supersymmetry is 48 = 3 × 16, equal to the number of quarks and leptons (including right-handed neutrinos) in three generations (see “The many lives of supergravity”). To go beyond the partial matching of quantum numbers achieved so far will, however, require some completely new insights, especially concerning the emergence of chiral gauge interactions.

    I think this is an interesting perspective on the main problem with supersymmetry, which I’d summarize as follows. In N=1 SUSY you can get a chiral theory like the SM, but if you get the SM this way, you predict for every SM particle a new particle with the exact same charges (behavior under internal symmetry transformation), but spin differing by 1/2. This is in radical disagreement with experiment. What you’d really like is to use SUSY to say something about internal symmetry, and this is what you can do in principle with higher values of N. The problem is that you don’t really know how to get a chiral theory this way. That may be a much more fruitful problem to focus on than the supposed hierarchy problem.

  • Progress in geometric Langlands marches on, with a new paper yesterday from Aganagic, Frenkel and Okounkov on the Quantum q-Langlands Correspondence, a two-parameter generalization of geometric Langlands. Among many other things, they formulate (Conjecture 6.3) a conjecture generalizing the characterization (using BRST methods) of affine Lie algebra representations at the critical level that from the beginning of the subject described a major aspect of how geometric Langlands works locally (for details on this, see Frenkel’s book Langlands Correspndence for Loop Groups).
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59 Responses to Various and Sundry

  1. BCnrd says:

    The end of the blackboard article, where they say that chemists have moved beyond blackboards, is not correct — at least not universally so. At my university a new “Science Teaching and Learning Center” just opened up, as a renovation of the “Old Chem” building which had been abandoned since the late 1980’s (due to safety concerns for earthquakes, I believe). The Chemistry department was adamant that the lecture rooms in this new building must have blackboards. The request was denied, but nobody told them until the building was unveiled last month and it was noticed that there were whiteboards everywhere. Some baloney was offered about high-tech markers and space-age “erasers” that are crap.

    The Chemistry faculty were livid, offering multiple reasons why they absolutely prefer blackboards to whiteboards for teaching purposes. They were very pleased that Math is standing alongside them in this matter. So now Chemistry and Math have jointly protested, and hopefully by the summer the whiteboards will be swapped out for blackboards. Then I can move on to undo the damage in the History dept. from last summer when workmen came in unannounced one day and swapped out all blackboards for whiteboards…

  2. How many boxes of Hagoromo chalk did you buy, BCnrd? I’ve heard it was a lot…

  3. Peter Woit says:

    For the Hagoromo chalk story, see
    In that story, a “15 year supply” for BCnrd is specified.

  4. BCnrd says:

    David, after that Japanese film crew visited here to make the US portion of their Hagaromo documentary, I decided to stock up some more for the apocalypse (not realizing that the company would come back into existence in South Korea some months later). I contacted my supplier in Oakland and she made some final drop-offs on campus with her dwindling goods from the back of her van. The campus police walked by during the transaction but had no idea what was inside the packed boxes. I now have what I estimate to be a 20-year supply in my office. It fits snugly inside some cabinets.

  5. Jeff M says:

    I hate whiteboards. At my university, the reason given for switching to whiteboards has been that chalk dust is bad for computers, which is just BS. I seriously hope we go back soon. Last semester I was lucky enough to have both classes in a blackboard room 🙂

  6. J.J. Green says:

    With reference to blackboards in toilets, they can be found in the Newton Institute in Cambridge.

  7. Magnema says:

    Worse than either chalkboards OR whiteboards is having both in the same room. Yes, I have seen this. Chalkboard at the front, whiteboard on the side, and another chalkboard in the back. At teacher’s request, in that room, the back and side were swapped, approximately mid-semester.

  8. anon says:

    I often worry that I am being poisoned by the whiteboard marker fumes I am forced to breathe (and probably absorb through the skin) at my institution. I have a macular degeneration condition whose symptoms are always worse after teaching.

  9. There were blackboards in the toilets at the Erwin Schrödinger Institute when I was there in 2006.

  10. srp says:

    OK, troglodytes, stick to your blackboards, which are indeed wonderful for the first strokes but completely suck once you start erasing and rewriting. In the U.S. I suspect this may be an East Coast (blackboards) versus West Coast (whiteboards) thing, with the ivy-covered traditionalists stubbornly sticking to the dirty, less-readable, fewer-colored, chalk-breaking and squeaking blackboard.

  11. Jon Awbrey says:

    Techtonic Shift — it was the subduction of disk drives that caused the upthrust of chalk and slate.

  12. Jeff M says:

    @Jon Awbrey

    Yes indeed, now that everything is solid state, the excuse for whiteboards is dead. Still have to convince the IT people. As for @srp, sorry, whiteboards never erase properly. The markers dry out, often several times in the same lecture. How many times have you gotten to a room with 15 whiteboard markers, none of which work? The markers smell. No comparison. As to East versus West, interesting thought. First time I remember being stuck at a whiteboard was a conference at the University of Washington, in ’93. So maybe….

  13. Radioactive says:

    While Max Tegmark’s ideas maybe wrong, I have much more sympathy for them than for Inference – a magazine which seems to consist completely of cranky letters from retired professors.

  14. paddy says:

    On chalk: On my first day of crumbly chalk teaching in West Africa in the late 70’s, I walked into the staff room covered head-to-foot with white dust after class. The head master smiled at me and said something to the effect that this was a sign of a hard working teacher. Thereafter I could never do wrong in his eyes.

    On the Tegmark reviews (and multiverse): As a lowly experimentalist with no philosophical training my main issue has always been whether probability arguments are being used where probability arguably does not apply–i.e., where one does not have clearcut arguments that the idea of an ensemble pertains. Moreover in some twists (multiverses) it would seem that positing the applicability of probability begs the question.

  15. What you’d really like is to use SUSY to say something about internal symmetry, and this is what you can do in principle with higher values of N. The problem is that you don’t really know how to get a chiral theory this way.

    There is a program dealing with this: first uplift the extended SuGra theory back to d=11 (that’s how N=8 d=4 was constructed in the first place) then compactify on ADE-singularities. This goes back to around Acharya-Witten 01 . This program is called “M-theory phenomenology”.

  16. Chris Kennedy says:

    A third thing: I had a great freshman chem professor who used an overhead projector. Sure he was motionless, less animated but he was able cover more material per hour and allowed us to realize our potential since less time and energy was wasted on kinetic motion.

  17. Peter Woit says:

    I’m sure Nicolai is well aware of that idea, didn’t mention it because he was suggesting not pursuing complicated old ideas that don’t work, and instead look for something new that does.

  18. C. Denson Hill says:

    The reason(s) mathematicians very strongly prefer blackboards:
    1. Ever try to write a complicated formula, with many indices upstairs and downstairs,
    with indices on the indices, perhaps with double summations up in an exponential
    under some integral signs, with complicated limits of integration? It is virtually
    impossible with (dried up) markers…and because of the chisel tip on (even a wet)
    marker, the width of the line you get depends on the direction of motion. And the
    coefficient of friction prevents good penmanship. Result with markers is sloppy and
    virtually unreadable.
    2. The speed at which you can write a legible statement of hypotheses and conclusions
    of a theorem or lemma is perfectly suited to the speed of comprehension in the audience. Unlike slides, projectors, or god forbid reading bullit points, which is like
    3. Marker dust is far more toxic than chalk dust.
    The only people who like white boards are those whose lectures require very little
    writing during the lecture. At my university, a certain provost decided to replace
    all blackboards by white boards…for no good reason…and we mathematicians rose
    up and got him fired. You should all do that!

  19. Jonas says:

    Interesting to see so many claim that mathematicians prefer blackboards. It is certainly not true to the degree that some here seem to think.

    In my own department, a rather large marh one, the overwhelming majority prefer whiteboard and that is why we have now gotten rid of all but one of the blackboards in our building. The only one left has been kept for a few years extra but we’ll soon get rid of that too.
    The only ones in the department who preferred blackboards when we changed boards were some in the then 60+ age range, but they have all retired by now. None among the younger have asked for the blackboards back, and we do give proper lectures with lots of writing, and we never use projectors and slides in teaching.

    I’ve never had a “dry” marker in years. Put the cork back on, remember to put the empty ones in the recycling bin, and you have no such problems.

  20. Bill says:

    One can tell a good math department from a bad one by a number of people who prefer blackboards to whiteboards.

  21. srp says:

    The dried-up marker issue is easily dealt with in the same manner that chalk users do–bring your own chalk (the chalk lying around is usually broken or stubby) = bring your own markers. (There will often be some duds left for you by others in the room, but also usually some that work fine.) It is easy to control a dry-erase market to write at any size–I have no idea what CDH above is talking about. As for the erasing ability of the two, a whiteboard marker is much, much easier to completely erase than a chalk mark, especially if you use the green marker.

    I wonder if my West Coast hypothesis holds for Jonas.

  22. Jeff M says:


    White boards never completely erase. Ever. Blackboards do build up dust, but a quick wipe with a wet anything fixes that. And I always bring my own markers but feel ridiculous going through 100 markers a semester, especially when I know every single other person is too. I would bet you that the average time a white board marker lasts is less than one lecture, even for people who are good at putting caps on. White board markers are much less precise than chalk. There is less feedback. Just one more way the east coast rules 🙂

  23. Peter Shor says:

    In my experience, good-quality whiteboards actually work well … you can erase them completely, and they stay erasable for a number of years.

    However, most whiteboards you actually run into are inferior-quality whiteboards, which are much worse than the average blackboard. I don’t know what the price difference between the good whiteboards and the bad whiteboards is, but I suspect it is substantial. I also don’t know which brands or surfaces are good.

  24. Jeff M says:

    Peter Shor,

    I totally believe that good quality whiteboards can be reasonable. But even you say “stay erasable for a number of years.” A good blackboard is erasable for 50 years. Maybe longer.

  25. Giotis says:

    Regarding the Langland’s paper by Frenkel et al.

    Its outcome means that (as suspected) stringy degrees of freedom (i.e. 6d (2,0) Little String Theory which is just a limit of type II ST) are needed for the physical counterpart of the quantum deformed Langland’s correspondence and thus the correspondence doesn’t stop at 6d (2,0) SCFT.

    Remember that the little strings of (2,0) LST are not the tensionless solitonic strings of (2,0) SCFT coming from D3 branes wrapping 2-cycles, they are fundamental strings of type II when we take the string coupling to zero limit.

    By all accounts this was anticipated from string theory point of view, since the (2,0) LST is the high energy limit of (2,0) SCFT, but not from field theory point of view since (2,0) SCFT is perfect on its own.

    Thus string theory is required instead of being a redundant description of a deep mathematical correspondence which implies the N=4 SYM S-duality i.e. of the YM Montone-Olive duality conjecture which is an extrapolation of the electromagnetic duality.

    The implications are indeed profound; Nature via mathematics (and vice versa) requires Strings.

  26. Richard Séguin says:

    Chalk dust is probably not good for your lungs, and the solvent in markers is undoubtedly toxic. It would be instructive to survey users and look for increased COPD in chalk users, and increased cancers in white board marker users. Personally, I find the solvent smell from markers to be much more repulsive than chalk dust.

  27. theoreticalminimum says:

    What about using a Windows-operated convertible laptop with Windows Journal (much like what Nima Arkani-Hamed does with a convertible Lenovo Thinkpad) connected to a projector to lecture classes? I have been doing this for a few years now. It very simply solves all of the above-mentioned toxicity issues, and there are many obvious added advantages.

  28. chiz says:

    Types of whiteboard:

    Enameled whiteboards, also referred to as porcelain, and sometimes glass boards, have the advantage that markings can be erased completely; other materials tend to become stained over time. Enameled boards are more expensive and less used in commercial environments, but in more demanding environments with heavier use, such as educational establishments, porcelain boards are considered superior.

    The solvent for marker pens is ethanol (safe) and isopropanol (not so safe).

  29. Petite Kabylie says:

    I am using usual power-point slides and they work fine. I think as long as one puts in all the steps in one’s derivations and synchronises one’s rate of changing slides with the flow of ideas in one’s lecture neither blackboards nor whiteboards compare.

  30. G. S. says:

    If Hollywood has taught me anything, it’s that true groundbreaking work is done not on blackboards or whiteboards, but on clear glass dormitory windows.

  31. Peter Woit says:

    Yes, one can look at a complicated and interesting story about mathematics and just get out of it “string theory rules!”, which is both stupid and boring. Enough.

  32. BCnrd says:


    I am at Stanford, and I know from experience here and at the math departments at UCLA, Caltech, and Berkeley as well as at MSRI there is no evidence in favor of your “East vs. West” hypothesis. Even at CCR West, the room set up for seminar talks by visiting mathematicians has blackboards. On the other hand, the West Coast is a veritable “multiverse” of colleges and universities, so perhaps somewhere out there is evidence in favor of any hypothesis. 🙂

  33. Maximillian G. Tresmond, Esq. says:

    Whiteboards could be the bane of a law school student’s existence. The fumes given off by some of those chisel tips leave you wondering if they should be on a DEA schedule.

  34. Jim Clarage says:

    Another subtle problem with dry-erase involves color. Not all humans perceive color the same, either physiologically or psychologically. Some eyes (like mine, mildly color-blind) perceive no contast of green markers on white boards, yet I know professors who prefer to write in green (or use it since all the “other colors” are dried up on that day). Some students have told me they can see black-marker best, others say blue is most visible, while others say green (about 40-40-20 in my surveys). On the psychological side, many professors (or students called up to the board) will use red-marker, which to many eyes just screams error-error-panic.

    p.s. I’d like to know what markers Jonas orders which never go dry. And what recycling service he has which actually can handle the rigid plastic in e.g., Expo markers. (only certain plastics can actually be recycled once they get to the plant, many just end up being burned, like the inner casing inside the old marker surely is).

  35. srp says:

    BCnrd: Interesting. There definitely seems to be such a coastal distinction in econ departments.

  36. milkshaken says:

    re solvents in erasable markers: it is not true isopropyl alcohol is unsafe, it is one of the least toxic solvents: you can actually ingest it in non-denatured form (up to a spoonful, not more) even if the taste is unpleasant. But xylenes are worse, and you can definitely smell those in some erasable markers we use – it smells like petrol and paint thinners.

  37. Tim says:

    Yup, I’m not sure why people who dislike whiteboards want to go overboard with false claims about health risks … the number of cancers due to white board markers is probably less than the number of verified predictions of string theory.

    If you like chalk and blackboards, that’s fine, but don’t make up “facts” to support your position. There’s far too much of that going around these days.

  38. Tim May says:

    I was at Intel (the company, not the intelligence agencies!) from 1974 to 1986.

    Whiteboards and dry-erase markers were all we ever had. A big change from the blackboards and chalk we had in college

    The whiteboards always caused me to feel “light-headed.” I never learned why this may’ve happened. I tried directly “smelling” one around 1978 or so and nearly passed out. I had to use them, given my job, but avoided them as best I could.

    (I still don’t know. But I avoid whiteboards and dry erase markers like the plague.)

  39. Jeff M says:

    I think some people are sensitive to whiteboard markers. I certainly am, I’m sensitive to latex paint too. And my wife is an artist, we had a loft for years in Brooklyn and I had to live with paint smells constantly 🙂 On another note, and I assume Peter will take this down, I don’t understand why I can’t mention my shock that a famous physicist like Tegmark doesn’t understand infinity, when Peter himself posted two reviews which say exactly that.

  40. Perpetual Student says:

    @Jeff M
    I can report that the U.Washington physics dept these days has plenty of blackboards, having cursed the glare that can make some of the chalk writing all but invisible.

  41. John says:

    Are all the SUSY bets based on N=1 or is this a way around resolving those bets?

  42. Peter Woit says:

    All SUSY bets and discussion of SUSY at the LHC is based on N=1, since higher N theories as conventionally understood are incompatible with what we know already about the Standard Model (chiral gauge couplings). As Nicolai comments, to use higher N in the way he suggests requires “some completely new insights”, something we don’t now understand.

  43. Frog Leg says:

    Sensitivity goes both ways. I have to wear gloves if I have write on a chalkboard; the feel of a chalkboard against my hand is very painful (as is the sound). The smell of dry erase markers does not bother me at all.

  44. serious question here says:

    is string/m theory based on susy N=1, or higher N?

    is 11D SUGRA that is the low-energy limit of M-theory N=1 or higher N?


  45. DoZen says:

    I’m very glad to hear Columbia is setting the pace for a blackboard renaissance.

    The squeak problem of chalk seems to depend partly on the quality of the chalk,
    but mostly on the experience of the writer- it never squeaks on me.

    Memories: when I visited Yale, a regular diversion in seminars was Serge Lang yelling “break the chalk”! at the speaker, then watching the befuddled speaker trying to figure out what they’d done wrong (Lang’s theory being that breaking the chalk destroys the resonances necessary for squeaking- but I prefer long chalk and never have that problem).

    Power point and its cousins predictably put the audience to sleep, for multiple obvious reasons:
    -the light is low so dozing off is encouraged;
    -too often the lazy prof is reading from their own slides prepared days or months ahead while having forgotten how the proof actually goes, and arrogantly and wrongly thinking they can think while trying to read and decipher what is there above and beyond them;
    -the definitions or key formulas are scattered on previous pages, making it impossible to follow the logic…
    Result: I have seen maybe 2 effective PP presentations in years of conferences.

    By contrast, in a board talk the presenter is forced to make the material come alive, as their brain is actively engaged in re-creating the math. They are more likely to look at the audience for feedback, rather than at their own slides. That is more fun for all concerned. Since one is not locked in to an order, a good speaker can change the order, emphasis, content completely in response to questions and the flow of the talk.
    (I have often realized while walking to the lecture -whether a course or a seminar- that it would be much better to totally invert the order- or even to change the subject!)
    A whiteboard talk is in-between. I agree with all criticisms voiced here. Chalkboard is best for both the presenter and audience, with absolute best being real slate with good-quality chalk. This is not just true for letters, but also for diagrams and illustrations- try drawing a sphere with chalk versus with a slidy stinky marker.

    A related new problem is that kids in school may not be learning good pensmanship,
    and lately even may not learn to write (or read) cursive at all. This is a developing disaster. At a board, having to print letters slows one down too much, and is much more tiring on the arm and hand. But those who never learned how to write properly will never know the difference. As the products of such misguided educational “reform” filter up to faculty level, we’ll likely see -and sleep through- more and more PP talks.

  46. bob sykes says:

    In 1970, I began my career at Union College, Schenectady, NY. The old Carnegie Bldg then had polished, black slate blackboards. In the whole 37 years of my career, using every kind of writing surface invented, nothing ever came even close to the perfect of those blackboards.

  47. I thought that article on blackboards was quite poor. The author never addressed the basic question – why do many mathematicians, more than other scientists, prefer blackboards?
    The answer has to be that the blackboard suits mathematics better than other subjects. Which suggests that the blackboard is very suitable for writing equations, since math lectures tends to contain more equations than other areas of science. And the reason for this last is not hard to fathom – the friction of chalk and board creates a pace that is just about right for talking and explaining math. QED

  48. P.S. I discovered a while ago that writing on a blackboard used by Einstein during a lecture at Oxford in 1931 contains a numerical error, an error that casts useful light on a puzzling mistake in a cosmology paper he published that year. (Einstein’s ‘Oxford blackboard’ is quite well known, but no one noticed the error). If whiteboards existed in 1931, I doubt Einstein’s mistake would still be visible!

  49. Jeff M says:


    I just looked up Einsteins blackboard at wikipedia, thanks for making my day 🙂 I can’t believe I never heard of it before, I’ve even been to Oxford. Of course, our tour guide was a friend of a friend who took us all over, but he had been a student of politics so we didn’t make it to the museum of science. Did make it to several wonderful 500 year old pubs though.

  50. C Denson Hill says:

    1.Probably many of you are too young to have ever experienced the sublime pleasure
    and satisfaction of lecturing on a real slate blackboard with good quality chalk. The
    lines are crisp and clear, the coefficient of friction is perfect to create a Palmer-like
    script, which is beautiful and easily read, and erasure is clean. You and the students
    leave class in a good mood.
    2. But then I have noticed that many people in physics are unable to write (script),
    and can only print…which usually makes the precise statement of any theorem too
    3. Finally, if you think a canned lecture, prepared in advance, via some sort of laptop
    presentation is the way to go, then I suggest you just email the pdf file to the students,
    and they (and you) do not have to go to class…all spontaneity is lost…just have them
    buy the book, and you can dispense with classes and lecturing altogether.

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