# Various and Sundry

• The MacArthur Foundation today announced “Genius” grants of $625,000 to 21 people, including two mathematicians, Jacob Lurie and Yitang Zhang. While there was a time these awards often went to mathematicians and theoretical physicists (the 1987 winners included string theorists Dan Friedan, David Gross, John Schwarz and Steve Shenker as well as mathematicians Robert Coleman and David Mumford), that has been much less common in recent years. Zhang, now a professor at the University of New Hampshire, is a perfect candidate for the award, unrecognized by academia (he worked at a Subway for a while) while he was doing brilliant and important work in number theory. Lurie is undeniably a genius, but kind of the opposite of Zhang, someone whose talents and work have been very well-recognized and rewarded already. He’s a Harvard professor and in November will be collecting a$3 million Milner-Zuckerberg Breakthrough Prize.
The Wall Street Journal leads off their story about this with Lurie, characterizing him as “A mathematician offering his book free on the internet”, implying that’s what distinguished him for the award from the other possible genius candidates:

This year’s winners span in age from 32 to 71 and include nine women and 12 men. A common thread: The winners reach their audiences in surprising places.

“This year, we have several people who one might describe as being engaged to challenge the rest of us to be lifelong learners outside the traditional classroom,” said Cecilia Conrad, who directs the fellows program as a vice president of the foundation. “It’s new solutions to old problems.”

Mathematician Jacob Lurie, who was honored for redefining models in algebraic geometry, negotiated with his publisher to make his book on math principles available for free download on his personal website. While academics sometimes place papers online free, putting a whole book online isn’t yet standard practice, according to the 36-year-old Harvard University professor. “From my point of view, the benefit of writing a book is for people to look at it. I would like as many people as possible to look at it,” he said.

The book in question is the 2009 944 page Higher Topos Theory, available on Lurie’s web-site here. He has just put up on his website an updated version of his second book, the 1178 page Higher Algebra. For those mathematicians worried that they might have trouble reading these because of a lack of physics background, Lurie himself reassures people here that

Since no knowledge of modern physics was required to write any of these books and papers, I can’t imagine that you need any such knowledge to read them.

In other Lurie news, he has also just put up on his web-site an important new paper, a first draft of joint work with Gaitsgory on the proof of Weil’s Tamagawa number conjecture for function fields.

• Skepticism about string theory and the multiverse abounds these days. A wonderful New York Times profile of Peter Higgs ends with

This has led some theorists to propose that our universe is only one in an ensemble of universes, the multiverse, in which the value of things like the Higgs is random.

Asked about that, Dr. Higgs lit up with a big grin. “I’m not a believer,” he said.

“It’s hard enough to have a theory for one universe.”

In Scientific American, George Ellis has a piece entitled Why the Multiverse May Be the Most Dangerous Idea in Physics.

Meanwhile, from a Templeton Foundation-financed conference on the Philosophy of Cosmology in the Canary Islands, Sean Carroll reports via Twitter that string theorist Tom Banks is arguing that “string theory has failed as a theory of our world.”

• Commenter Shantanu pointed out something I hadn’t realized, that David Gross will be here in New York this week, giving talks at NYU. Unfortunately I won’t be able to attend, in particular I have to teach at the time of his colloquium on Tuesday. Perhaps someone who can attend will report what he has to say.
• In Grothendieck news, the English translation by Melissa Schneps of Winfried Scharlau’s book on the later period of Grothendieck’s life has started to appear, see some chapters here.

A wonderful book of articles about Grothendieck’s mathematics, Alexandre Grothendieck: A Mathematical Portrait, edited by Leila Schneps, has recently been published (with a version of the articles also available here).

Update: Vigorous back-tweeting (see here, here, here, here and here) now going on from Sean Carroll and Tom Banks. Admitting that string theory unification has failed is just not done. Revised and extended remarks from Tom Banks add praise for the greatness of string theory and avoid the word “failure”:

Without string theory we would never have been in a position to understand anything serious about quantum gravity, but without going beyond the present understanding of string theory we can make no further progress.

This still though reads as “string theory is at a dead end”. Sean echoes the praise:

conventional string theory has given us enormous guidance toward quantum gravity.

and dismisses the failure issue as something obvious and not worth mentioning:

Need to go beyond is obvious.

I guess I should point out that it is not obvious that you need to go “beyond” string theory, in the sense of farther in the same direction. Might be that you need to abandon the direction that led you to a dead end, back-track, and try a different one.

Strange thing is that this discussion of a string theory dead end just seems to be about problems using string theory to do quantum gravity when there’s a positive cosmological constant (otherwise, according to Carroll, “String theory is great”). The idea of string unification seems to be so dead it’s not even worth mentioning.

Update: Shaun Hotchkiss has the latest news on Planck/BICEP2 and dust here. People are still scraping data off old Planck slides, with real Planck data on the BICEP2 patch rumored to be imminent for the past month or so:

Any day now we are to expect Planck’s paper revealing the non-conference-talk maps of the high frequency polarisation signal along BICEP2’s line of sight. These will just be images though, not raw data. The word on the street/corridor is that a fully written draft exists and has clearance to be submitted and nobody I’ve spoken to knows why it hasn’t been. The sort of phrases I’ve heard about what to expect from this is that “it will clarify a lot of things”, but “it won’t be conclusive”.

Update: Two more. I’ve been avoiding writing about the AMS-02 announcement about the positron excess, waiting to hear something sensible about its significance. Resonaances is on the job, giving an interesting take on the data, and claiming this has nothing to do with dark matter.

There’s a nice profile of Robbert Dijkgraaf here.

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### 17 Responses to Various and Sundry

1. george ellis says:

Peter, you link to an article by me on multiverses that has appeared in SciAm with title “Why the Multiverse May Be the Most Dangerous Idea in Physics.” This just shows the dangers of having subeditors assign titles to what you write, without consulting when they do so. I do not agree with that title, and disassociate myself from it.
What is dangerous is weakening the criteria for what science is. Multiverses are only dangerous to science if they are used to motivate that move. String theory is of course another theory that has also been used to motivate that move. It is that move that is dangerous to science, not the theories that are defended in this way.

2. Peter Woit says:

George Ellis,
Thanks for the clarification. My own version of this point would be that the problem with the multiverse is that it is being used to cheat, to evade having to acknowledge the failure of the idea of string theory unification.

3. Jon Orloff says:

I really dislike the term “genius awards,” as the word genius is, I think, greatly overused. Aristotle was a genius. Newton was a genius. J.S. Bach was a genius. If you do something comparable to their work, you deserve to be called a genius.

4. As for the Grothendieck news, I would like to stress that the fund-raising effort to collect money needed for the translation is still ongoing – see http://www.gofundme.com/7ldiwo (still almost \$3000 to go…). Please contribute and spread the word!

5. HL-LHC or HE-LHC says:

“Sean Carroll reports via Twitter that string theorist Tom Banks is arguing that “string theory has failed as a theory of our world.”

can you clarify Tom Banks’ view? is it that string theory is wrong, or is it not even wrong? what evidence or arguments persuade him? is he abandoning string theory for some other line of research? what is his preferred BSM and QG research?

6. Casey Leedom says:

George F. R. Ellis,

Ignoring the editorial sub-title that was thrust upon your article, I’m confused about one sentence in it: “Astronomers are able to see out to a distance of about 42 billion light-years, our cosmic visual horizon.” I thought we were only able to see backwards in time to about 13.7 billion years. Even if we double that for an edge-to-edge, 180˚ view we still only get 27.4 billion light years. Where’s the “42” come from?

7. S. Molnar says:

Zhang recently gave a public lecture at IAS. I can’t find the video on the IAS website, but here is a link on another website:
http://video.ust.hk/Watch.aspx?Video=E05D054DB6D058F6

Casey Leedom: I think we all know where the “42” comes from, but it’s news to me that it has units of billions of light years.

8. S. Molnar says:

Correction: It must be a different IAS than the default, which confused me.

9. Casey: the distance we can see out to is not simply (age of the universe) x (speed of light). Perhaps this will help. (The precise numbers depend on the values of cosmological parameters, which have been updated since Planck though that page hasn’t, hence the difference of 47 vs 42.)

10. george ellis says:

Casey Leedom: its basically because the expansion rate has not been constant over time. The universe was expanding faster at earlier times. You have to do an integral of 1/a(t) where a(t) is the scale factor to determine how far we can have seen. This gives a factor of about 3 extra over the present Hubble scale.

11. george ellis says:
12. Peter Woit says:

HL-LHC or HE-LHC,
Use of the “failure” word seems to have gotten Banks in trouble, see the update to the posting. Banks for a long time has had his own alternative to string theory “Holographic Space-Time”, see for example
http://arxiv.org/abs/1109.2435

13. HL-LHC or HE-LHC says:

@Woit
yeah at the time of the comment i read the original post before the update.

It appears Tom Banks agrees with you on string theory unification.
I know this is outside your expertise, but is string theory a successful theory of QG, or has string theory provided us with a important insights into QG? Should string theory research continue on as a theory of QG – irrespective of its theory as GUT type unification?

14. Geoff says:

Is there some unspoken agreement that even the preface to a mathematical monograph has to begin with “Let…… ” ?

15. Peter Woit says:

HL-LHC or HE-LHC,

My non-expert impression of string theory as QG research is that the last significant new idea was AdS/CFT 17 years ago, and that much of the work since then has been based on trying to figure out how to use gauge/gravity duality to think about QG. Both Banks and Carroll seem to be admitting that this doesn’t work as hoped, at least for positive cosmological constant. The “firewall” business of recent years is based on the realization that it doesn’t work to solve the black hole information paradox as hoped.

What’s interesting about the Carroll tweets I think is that they show what happens when a realistic description of the situation slips out. This must quickly be remedied by larding it with hype.

People who have ideas about how to make progress on string theory as QG should do so. People who don’t should consider working on something else.

16. jd says:

There is an article on AMS-02 on CNN. The publicity machine seems to be alive and well.

17. Peter Woit says:

jd,
Yes. Headlines like “AMS Space Experiment Sees Hints of Dark Matter Particles” can’t be blamed on journalists. CERN put out a press release
http://press.web.cern.ch/press-releases/2014/09/latest-measurements-ams-experiment-unveil-new-territories-flux-cosmic-rays
claiming “tantalizingly consistent with dark matter particles with mass of the order of 1 TeV” and the APS summarizes the AMS-02 PRL as “More Dark Matter Hints from Cosmic Rays?”
http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.113.121102

At Resonaances, Jester explains the actual situation:
“The dark matter explanation is unlikely for many reasons. On the theoretical side, the large annihilation cross section required is difficult to achieve, and it is difficult to produce a large flux of positrons without producing an excess of antiprotons at the same time. When theoretical obstacles are overcome by skillful model building, constraints from gamma ray and radio observations disfavor the relevant parameter space. Even if these constraints are dismissed due to large astrophysical uncertainties, the models poorly fit the shape the electron and positron spectrum observed by PAMELA, AMS, and FERMI (see the addendum of this paper for a recent discussion). “