Various News

Posted on February 22, 2017 by woit

First some mathematics items:

  • Igor Shafarevich, one of the great figures of twentieth century algebraic geometry and algebraic number theory, died this past weekend at the age of 93. Besides his many contributions to mathematics research, he was also a remarkably lucid expositor. His two volume Basic Algebraic Geometry is a wonderful introduction to that subject, his survey volume Basic Notions of Algebra emphasizes the connections to geometry, and his volume on number theory (with Borevich) struck the AMS reviewer as “delectable”.

    Shafarevich was also known for his religiously-motivated nationalistic views which to many were distressingly anti-Semitic. In the spirit of respect for the recently deceased, I’ll just link to a quite interesting recent discussion (very sympathetic to Shafarevich) of the issue by David Mumford here (and ruthlessly delete attempts to argue about this in the comment section).

  • The AMS Notices has a set of articles in honor of Andrew Wiles and his work, which include some great explanations of the mathematics, as well as a long in-depth interview.
  • For another detailed interview with a mathematician, see Quanta magazine for a piece by Siobhan Roberts about Sylvia Serfaty of the Courant Institute.

On the physics front, there’s:

  • For his contribution to the Why Trust a Theory? conference (see here and here), Helge Kragh has a new paper which examines the question of whether history of science can help evaluate recent claims about the need to change the way theories are assessed. He sees in the unsuccessful “vortex theory” of the late nineteenth century an analog of string theory, with many of the same claims and justifications for lack of success. He quotes as a typical example of the enthusiasm of the time:

    I feel that we are so close with vortex theory that – in my moments of greatest optimism – I imagine that any day, the final form of the theory might drop out of the sky and land in someone’s lap. But more realistically, I feel that we are now in the process of constructing a much deeper theory of anything we have had before and that … when I am too old to have any useful thoughts on the subject, younger physicists will have to decide whether we have in fact found the final theory!

    but then explains that this is actually a quote from Witten, with “string” replaced by “vortex”.

  • Scientific American this month has an article (also available here) about the problems with the theory of inflation. The authors end by pointing out the dangers to science of multiverse inflationary scenarios (which they call the “multimess”):

    Some scientists accept that inflation is untestable but refuse to abandon it. They have proposed that, instead, science must change by discarding one of its defining properties: empirical testability. This notion has triggered a roller coaster of discussions about the nature of science and its possible redefinition, promoting the idea of some kind of nonempirical science.

    A common misconception is that experiments can be used to falsify a theory. In practice, a failing theory gets increasingly immunized against experiment by attempts to patch it. The theory becomes more highly tuned and arcane to fit new observations until it reaches a state where its explanatory power diminishes to the point that it is no longer pursued. The explanatory power of a theory is measured by the set of possibilities it excludes. More immunization means less exclusion and less power. A theory like the multimess does not exclude anything and, hence, has zero power. Declaring an empty theory as the unquestioned standard view requires some sort of assurance outside of science. Short of a professed oracle, the only alternative is to invoke authorities. History teaches us that this is the wrong road to take.

  • Nautilus has an article by Juan Collar about the increasing skepticism about Wimps as dark matter candidates, and the interest in alternatives.

Update: With results from the full 13 TeV dataset just a few weeks away, SUSY enthusiasts have given up hope for the LHC. A new paper just out argues that pre-LHC claims that naturalness + SUSY implied a gluino mass upper bound of 350 GeV (the latest LHC limits are more like 1900 GeV, likely to go up next month) were misguided. According to these authors, the right number for the upper bound is 5200 GeV and the “HE-LHC with [cm energy] 33 TeV is required to either discover or falsify natural SUSY”. So, claims that the LHC could falsify natural SUSY are no longer operative now that it has done so by earlier metrics, and such discovery or falsification is still just around the corner. All that’s needed is to rebuild the LHC into a higher energy version (that’s what the HE-LHC proposal is, may take a while…).

Update: Another excellent article by Natalie Wolchover at Quanta, this time about progress in studying conformal quantum field theories in higher dimensions (above 2). Definitely one of the more interesting things going on in theory at the moment. The reference in the subtitle to “geometry underlying all quantum theories” I don’t think though is really justified, this is really just about conformal field theories.

There’s probably lots more to be learned about these, with this conformal symmetry still not fully exploited. I’m somewhat fond of the point of view that you really shouldn’t try and think of QFTs just as effective theories for some different physics at short distances. Rather, what might be going on at short distances is not some new kind of theory at the cutoff scale, but a conformal theory valid at all scales.

Update: From the comments, unfortunately two other deaths to report, those of Bert Kostant (I’ve written something here) and Ludwig Faddeev.

Posted in Multiverse Mania, Uncategorized | 15 Comments

A Big Bang in a Little Room

Posted on February 18, 2017 by woit

There’s a review in today’s Wall Street Journal by me of Zeeya Merali’s A Big Bang in a Little Room. If their version is behind a paywall you might find also find it elsewhere (for instance here). I’ll reproduce parts of the review below with some comments more appropriate for the blog venue. As always, the editors at the WSJ did an excellent job of improving the first draft I sent them.

Merali has a website about the book here, and last week Nature published this review by Andreas Albrecht. Albrecht criticizes the book for “sloppy interplay between science and religion”, but I think he misses the important point that the most serious problem here is the sloppiness about what is science and what isn’t. When physics journals decide to publish articles like this one, it’s not surprising that science writers make the mistake of taking them seriously and writing about them (Merali’s first chapter is about this paper).

Here are some extracts from the review, with some comments:

What happened at the Big Bang—or before—is an irresistible question but one that, for now, as science, lies in the realm of the purely speculative.

In “A Big Bang in a Little Room,” science writer Zeeya Merali turns the question around, asking instead whether physicists can create a “baby universe,” born in its own Big Bang. Indeed, one prominent theorist she interviews has suggested that our own universe might be a baby universe created by a “physicist hacker,” with the complex pattern of fundamental particle masses intended as some sort of message to us. thereby learning more about the beginnings of the “old” one.

The reference here is to Andrei Linde and this 1991 paper.

[Merali] explains that her interest in this topic is tied up with her religious beliefs: If we ourselves could play God and create a new universe, wouldn’t that creation amount to a theological discovery, showing the likelihood that some higher intelligence was responsible for the Big Bang? She structures her narrative around interviews with prominent theoretical physicists; they mostly discuss science, but religious questions sometimes play a role, with often fascinating results. While some refuse to engage, she gets others to discuss such topics as the relation of the laws of physics to God’s happiness, the possibility of a physical “consciousness field,” and what the quantum mechanics of the Big Bang might indicate about the possibility of life after death and resurrection.

Don Page is the one interested in God’s happiness, Abhay Ashtekar in the “consciousness field”, and Andrei Linde in resurrection.

Mr. Linde is the central figure in this story, and Ms. Merali describes him as “a showman: bombastic, passionate, and fueled by the certain belief that inflation theory, which he helped to invent, is correct.” While Ms. Merali takes all of this seriously, there are very good reasons why most physicists don’t. Readers of “A Big Bang in a Little Room” would be well-advised to enjoy the ride but stay skeptical. Inflationary models can to some degree be confronted with observation and tested (a topic covered in other books but not this one).

About the string theory landscape:

Ms. Merali gives a disturbing version of this, contemplating the possibility that “string theory and inflation may be conspiring against us in such a way that we may never find evidence for them, and just have to trust in them as an act of faith.”

This comes after an explanation of the anthropic multiverse point of view from HEP experimentalist Greg Landsberg, where he adds the twist of anthropics explaining why the string scale is at such high energy, and thus unobservable. The full paragraph in the book is

In other words, the physics of string theory and inflation may be conspiring against us in such a way that we may never find evidence for them, and just have to trust in them as an act of faith. The multiverse truly works in mysterious ways!

If that paragraph doesn’t make a scientist’s blood run cold and see the danger physics is facing, I don’t know what will. I end the review with

In an era where “post-truth” was the word of the year, scientists and science writers need to make clear that science is not a species of theological or philosophical speculation and not about belief or entertainment value. Legitimate scientific claims are those that can be backed up with evidence, and unfortunately the wonderful and exciting story told well here contains none at all.

My concern about the topic of the book is that it’s Fake Physics, not that religion is motivating the author (and likely motivating the Templeton Foundation to fund this project). A book about the religious views of physicists would be an interesting one that I’d certainly read, and the material in this book on that topic is quite interesting. One of the odder twists here is that the two blurbs from physicists promoting the book are from Sean Carroll and Martin Rees, with Carroll writing

So you want to make your own universe. Zeeya Merali’s new book won’t quite give you an instruction kit—but it’s the closest thing we have at the moment. A fun and mind-expanding ride through modern ideas of how universes come to be.

I don’t see how you can be devoted to fighting for science against religiously-driven pseudoscience, and think that this book is one you’d like to see be the public face of what “modern ideas” about cosmology are.

Posted in Book Reviews, Fake Physics | 21 Comments

Various Links

Posted on February 10, 2017 by woit

The Columbia Math department has been doing extremely well in recent years, with some wonderful mathematicians joining the department. A couple items first involving some of them:

  • Kevin Hartnett at Quanta Magazine has a great article about developments in the field of technical issues in the foundations of symplectic topology. This explains work by my colleague Dusa McDuff, who together with Katrin Wehrheim has been working on such issues, trying to resolve questions raised by fundamental work of Kenji Fukaya and collaborators. For technical details, two places to start looking are here and here.

    The Hartnett story does an excellent job of showing one aspect of how research mathematics is done. Due to the complexity of the arguments needed, it’s not unusual for early papers in a new field to not be completely convincing to everyone, with unresolved questions about whether proofs really are airtight. The way things are supposed to work, and how they worked here, is that as researchers better understand the subject proofs are improved, details better understood and problems fixed. Along the way there may be disagreements about whether the original arguments were incomplete or not, but almost always people end up agreeing on the final result.

    Also featured in the article is another of my Columbia colleagues, Mohammed Abouzaid, who provides characteristically wise and well thought out remarks on the story.

  • Via Chandan Dalawat, I learned of an interesting CIRM video interview with another colleague, Michael Harris. The same site has this interview with Dusa McDuff, as well as a variety of other interviews in English and French.

For some other non-Columbia related links:

  • The 70th birthday of Alain Connes is coming up soon, and will be celebrated with a series of public lectures and conferences on noncommutative geometry in Shanghai.
    This year will be the last series of lectures by Connes at the College de France. They’re appearing online here, and I highly recommend them. He’s taking the opportunity to start the series with a general overview of the point of view about the relationship of geometry and quantum theory that he has been developing for many years.
  • For employment trends in theoretical particle physics, there are some updated graphs of data gleaned from the particle theory jobs rumor mill created by Erich Poppitz and available here. In terms of total number of jobs, there has been some recovery in the past couple years, with about 15 jobs/year, above the 10 or so common since the 2008 financial crisis (before 2008 numbers were higher, 20-25). As always, an important thing to keep in mind about this field is that this number of permanent jobs/year is a small fraction of the number of Ph.Ds. in the subject being produced each year at US universities.

    The numbers for distribution of subfields separate out “string theory” and lattice gauge theory. There have always been few jobs in lattice gauge theory, appear to be no hires in that subject for the past two years. I’m putting “string theory” in quotes, because it’s very hard these days to figure out what counts as “string theory”. With Poppitz’s choice of what to count, hiring in string theory has recovered a bit, now around 25% of the total for the past two years, up from more like 15% typical since 2006 (earlier on the numbers in some years were around 50%).

  • As pointed out here by commenter Shantanu, on Wednesday John Ellis gave a talk on Where is particle physics going? at Perimeter. I’d characterize Ellis’s answer to the question as “farther down the blind alley of supersymmetry”. He spins the failure to find SUSY so far at the LHC as some sort of positive argument for SUSY. The question session was dominated by questions about SUSY, with Ellis taking the attitude that there’s no reason to worry about the failure so far of the fine-tuning argument for SUSY, all you need to do is “ratchet up your pain threshold”. I fear that’s some sort of general advice where this line of research is going.

    About the failure to find any evidence for SUSY wimps that were supposed to explain dark matter, Ellis explained that he had been working on this idea for 34 years, first writing about it in 1983, so with that much invested in it, he’s not about to give up now.

Update: Davide Castelvecchi points me to another new mathematics story at Nature.

Update: One more. A profile of Roger Penrose by Philip Ball. Penrose explains that his main problems with string theory come from two sources. One is the instability problem of extra dimensions, the other is his aesthetic conviction that sticking to four space-time dimensions is a good idea since it is only in four dimensions that you get the beautiful geometry of twistors. Ball raises the interesting question of whether Penrose could have a successful scientific career if he were starting out today:

Worst of all, the career structures and pressures facing young researchers make it increasingly hard to find the time simply to think. According to several early-career scientists interviewed by Nature, the constant need to bring in grant money, to produce papers and administer groups, leaves little time to do any research, still less indulge anything so abstract and risky as an idea.

Posted in Uncategorized | 23 Comments

Perfectoid Woodstock

Posted on February 7, 2017 by woit

Every year in Tucson the Arizona Winter School takes place, with a five day program on some topic in arithmetic geometry aimed mainly at advanced graduate students, designed to get them involved in current research-level topics. This year’s topic (Perfectoid Spaces) is drawing a huge number of people there next month, with about 450 participants expected (in the past numbers were more like 100). This should be a veritable Woodstock of arithmetic geometry, with no one I’ve talked to quite able to figure this out, thinking that there probably weren’t 450 people worldwide interested at all in arithmetic geometry. It seems everyone in the field will be there and then some.

Peter Scholze is the opening and closing act. The other lecturers who will take the stage have started to put lecture notes for their lectures on the school website.

Some are dubious that there really are 400 or so students in the world with the background necessary to understand this material. See for example MathOverflow where nfdc23 isn’t very encouraging to a student who doesn’t know any rigid analytic geometry, but plans to attend the AWS. In any case, I hear Tucson is quite nice in March.

At some kind of other end of the spectrum of such things, a couple months later experts will gather in Germany to discuss this field (see here). Also for about five days, at the Schloss Elmau Luxury Spa and Cultural Hideaway, the sort of place heads of state go for G7 meetings. Rooms run $600 a night or so, but in this case the tab is being picked up by the Simons Foundation. Sorry, by invitation only.

Posted in Uncategorized | 22 Comments

Math and Physics Social Media

Posted on February 4, 2017 by woit

In the current situation, getting back to finding interesting news about math and/or physics to think about seems like a good idea, but I’ve been having trouble coming up with such news. Besides blogs, many of them listed on the right-hand margin of this one, I also follow some people on Twitter and on Google+. There are quite a few well-known physicists on Twitter at this point. On any given day you can learn something interesting from, for instance, Frank Wilczek or John Preskill (or see an epic throwdown between them).

I’m sure there are many other mathematicians and physicists on social media that I’m not aware of, and open here to hearing suggestions. Part of the problem is that I’m now so old I figure I don’t even know what social media sites are out there. I hear there’s this thing called Facebook, but also that it’s now over as far as the younger generation is concerned. So, if you have a suggestion about where to find high quality news about math or physics on social media, whether it’s on Twitter, Google+, Facebook, Live Journal, Instagram, Pinterest, Snapchat, Yik Yak, Grindr or something else I’ve never heard of, please let us all know in the comments.

Posted in Uncategorized | 17 Comments

Fascism and the Current National Emergency

Posted on January 28, 2017 by woit

After the election it seemed to me that it would be a good idea to ignore what Trump tweeted or said, and wait to see what he and the people he surrounded himself with would actually do. We’ve been finding this out over the past few days, and today the nature of the problem we face is now clear. The actions ordered today that are now being carried out by US officials around the world are the product of a deranged and dangerous personality who has surrounded himself with similar others. This is a national emergency with no parallel in our history.

While the US has never seen the likes of this situation, Europe has, with Trump following a playbook familiar from the history of the 1930s. At this point the US may be one terrorist attack away from full-blown Fascism, this time with nuclear weapons. This needs to be stopped, now.

The Constitution does provide two ways to deal with something like this: either the impeachment process or removal under the Twenty-Fifth Amendment as “unable to discharge the powers and duties of his office.” Many of Trump’s recent statements are clearly the product of delusional mind that is incapable of dealing with reality, and these delusions are now reflected in his actions.

Removing Trump and those he has surrounded himself with will require the cooperation of a significant number of Republican legislators. Anyone who cares about US democracy should be trying to figure out how to get this to happen. Those of us in the US desperately need some good ideas about how to do this. Those in other countries should be pressing their governments and institutions to fight back against the US, as well as doing what they can to keep their own societies from following the US down this path.

I’m moderating comments here and will only post one kind of comment: positive ideas about what to do about this emergency situation. At this point I think what’s needed are ideas way beyond suggestions of a “scientist’s march” to promote rationality. We need to figure out how to fight a new form of Fascism that has just come to power and is starting to rule by decree.

Update: With the Republican Congress so far deciding to sit back and let Donald Trump, Steve Bannon and Stephen Miller rule by decree, all hopes for now are with the Judiciary. Last night a judge issued an emergency stay on parts of the executive order, this was followed by a statement from Miller on behalf of the White House that the order “remains in full, complete and total effect.” The suggestion to donate to the ACLU is a good one, they are on the front lines here.

The President of my institution, Columbia University, at 1 am sent an email to the University community denouncing this executive order and involving the University in this in an unprecedented way:

As I have said on many occasions, it is critically important that the University, as such, not take stands on ideological or political issues. Yet it is also true that the University, as an institution in the society, must step forward to object when policies and state action conflict with its fundamental values, and especially when they bespeak purposes and a mentality that are at odds with our basic mission. This is such a case.

There is a petition being signed by academics here, which likely will have no effect, but I signed it anyway, and you may want to too.

Update: A small glimmer of hope: a joint statement criticizing the executive order by Republican senators McCain and Graham, and a Twitter response from Trump identifying any opposition from them as “looking to start World War III”. World War III between Trump and Republican senators is what we all need to root for.

Worth watching: news reports that the Trump administration is defying court orders requiring access to lawyers by detainees at Dulles airport. A decision by Trump and his people to defy court orders would provide grounds for impeachment.

Update: Just wrote the following to a correspondent, thought I might as well also post it here.

My advice would be to consider focusing on the following, and not getting distracted by the blizzard of appalling things one might reasonably find concerning about the current situation:

  • It was unclear who would actually be running things in a Trump administration (since Trump himself clearly neither knows nor cares about anything other than getting attention) until the past couple days. The answer now seems to be that it’s Steve Bannon of Breitbart. Bannon is a self-described “Leninist”, see for instance.

    His self-described goal is to tear the country apart: “to destroy the state… destroy all of today’s establishment.” This means he’s not just our enemy, but is also the enemy of much of the Republican Party, including for example John McCain and Lindsey Graham. He’s also not about to let himself be thwarted by the courts. I think we’re already seeing defiance of court orders, with a lot more of that to come.

  • There’s always the possibility of something like a military coup, but the only constitutional way out of this is impeachment or the 25th amendment route. This requires convincing a sizable number of Republican legislators that they have to abandon Trump and support his removal. To me, the big question here is what can be done to make that happen. How does one get the Republican establishment (legislators and/or Fox News, Wall Street Journal, etc.) to turn on Trump? My guess is that where they are now is that they know they have a problem on their hands, but are deathly afraid of Trump’s supporters, of ending up with their heads on a pike.
  • There’s not much time here. Looking at history, what happens next in this kind of situation is some episode of violence gets used to rally the country to the leader and justify his assumption of emergency power to rule by decree. We’re one episode of some enraged person shooting a lot of people away from that happening, in a country full of heavily armed angry people.
  • The best, most successful thing to hope for here is something I and maybe many of you find a depressing prospect: President Pence. But, there we are.

Hoping I’m wrong about all of this…

Update: Thanks to commenter Fred P. for the link to this. For something sensible from a conservative, see this by Eliot A. Cohen, which includes:

For the community of conservative thinkers and experts, and more importantly, conservative politicians, this is a testing time. Either you stand up for your principles and for what you know is decent behavior, or you go down, if not now, then years from now, as a coward or opportunist. Your reputation will never recover, nor should it.

Update: There was an incident last night (in Quebec City) of an enraged person shooting a lot of innocent people, killing 6 and wounding 8 others. Since the shooter was an Islamophobe and the victims were Muslims praying at a mosque, so this was of no use to Trump/Bannon, this has gotten just about zero attention.

Update: The Quebec City shooter was a Trump fan radicalized by Marine Le Pen.

Update: Terry Tao has a blog entry about this, emphasizing the damage to the math community.


Update: Leonard Susskind has also decided to issue a statement warning about Fascism and the Trump administration, using his YouTube channel.

Update: For commentary from historians of the rise of fascism in Germany on analogies with the current situation in the US, see Ron Rosenbaum and Isabel Virgina Hull.

Posted in Uncategorized | 52 Comments

Fake Physics

Posted on January 20, 2017 by woit

2016 so far wins my lifetime award for most depressing and disturbing year ever (on the front of the larger world one reads about in the newspaper and elsewhere, personally things are fine, thanks). Perhaps the most disturbing thing has been seeing the way in which people’s access to information about the larger world has become more and more dominated by what has become known as “Fake News”: stuff which is not true, but which someone with an agenda successfully gets others to believe. This is a problem that goes far beyond obvious nonsense fed to rubes on Facebook, to the point of including what a lot of my well-educated colleagues believe because they read it on the front page of the New York Times.

I have no idea what to do about this larger problem and no intention of further discussing it here. I’ve started to come to the conclusion though that the most disturbing trend in theoretical physics of recent years may best be understood as a related phenomenon: “Fake Physics”. The first few weeks of 2017 are seeing a flood of examples of what I have in mind, including for instance:

Note that the above examples are just ones written by physicists or reporting claims of physicists, there are also philosophers, theologians and others putting out similar articles, although without the claims to scientific authority coming from the physicists.

Fake Physics VII just appeared and is rather bizarre. It essentially argues that the idea of assuming a Multiverse and using it to make statistical predictions doesn’t work. But instead of drawing the obvious conclusion (this was a scientifically worthless idea, as seemed likely to most everyone else), the argument is that we need a “revolution in our understanding of physics” that will make the idea work.

Fake Physics shares several characteristics with Fake News:

  • It’s clickbait. While getting anyone to pay attention to the solution of a difficult technical problem in quantum field theory is likely to be nearly impossible, topics like “What happened before the Big Bang?” and “Did you know that there’s someone exactly identical to you somewhere else in the multiverse, and they’re dating Scarlet Johansson?” are sure crowd-pleasers. This motivates some physicists, and even more journalists, with the latter having the much better excuse that their livelihood depends on getting people to click on their stories.
  • It’s a propaganda tactic designed to mask failure. The main reason for the current mania for the Multiverse is the failure of the string theory unification program. Some who have invested their lives in this program have decided to use this sort of Fake Physics as an excuse to avoid admitting failure.
  • The group driving this is small but determined, ideology-driven and well-funded by rich people with an ax to grind. The majority of the community is unwilling to take on the unpleasant and unrewarding task of challenging them. While Multiverse Fake Physics plays a large role in media coverage of fundamental physics, partially because of funding from the Templeton Foundation, there are very few actual papers on the subject and “research” in this area is a small fraction of what theorists are doing. Most physicists just hope that if they ignore this it will go away.

Unfortunately Fake Physics is not going away, but becoming ever more widespread. While I don’t know what to do about Fake News, I think there still is a chance to successfully fight Fake Physics and hope others will help with this.

Update: There’s more

  • Fake Physics IX explains that the Many Worlds multiverse and the cosmological multiverse are one and the same. Sean Carroll is featured.
  • Fake Physics X includes the following from Carroll:

    David Chalmers does a wonderful job at making an important point: “A virtual world is just as real as a physical world.”… what’s real to one person might be virtual to someone else.

People at Hacker News are discussing this. There I’m accused of “misleading people” by making them think the cosmological multiverse is the same thing as the Many Worlds interpretation. Oy.

Update: Thanks to a commenter for pointing out Fake Physics XI, courtesy of Science Friday. As usual, the same vigorous ideologues promoting Fake Physics, the same dearth of voices pointing out the problems with it.

Posted in Fake Physics, Favorite Old Posts, Multiverse Mania | 61 Comments

Various and Sundry

Posted on January 13, 2017 by woit

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).
Posted in Uncategorized | 59 Comments

New Year’s Multiverse

Posted on January 7, 2017 by woit

I see little to be hopeful about the new year, but had a glimmer of a hope that we’ll see a reduction in Multiverse Mania. Surely people will sooner or later get tired of stale pseudo-science. Just got back to work from vacation and it seems that so far this is not working out at all, quite the opposite.

At the yearly Edge question site, Martin Rees’s answer to the question “What scientific term or concept ought to be more widely known?” is The Multiverse, and he starts out with the usual sort of breathless hype:

An astonishing concept has entered mainstream cosmological thought…

Critics of the multiverse are described as having two arguments:

  • “Some claim that unobservable entities aren’t part of science.”
  • “Some physicists don’t like the multiverse: they’d be disappointed if some of the key numbers they are trying to explain turn out to be mere environmental contingencies governing our local space-time patch—no more truly “fundamental” than the parameters of the Earth’s orbit round the Sun.”

The first of these is the usual straw man argument, painting multiverse critics as too ignorant to realize that much of science is based upon indirect evidence, not direct observation. The actual argument of this sort against the multiverse is not that we can’t get direct evidence for it, but that there is no evidence of any kind for it, direct or indirect, and no plausible prospects of getting any. This case has been made ad nauseam here on this blog.

The second of these arguments is treated in much more detail in a new article at Nautilus by string theorist Tasneem Zehra Husain with the title Even Physicists Find the Multiverse Faintly Disturbing. Husain treats in detail the question of how physicists “feel” about the multiverse, and like Rees, makes the point that what physicists don’t “like” about the multiverse is that it removes hopes of being able to do things like understand the nature and strengths of fundamental forces, or calculate the masses of elementary particles.

Rees tells us that physicists are wrong to feel this way, that instead they should be awed by “the revelation that physical reality was grander and richer than hitherto envisioned” and that “If we’re in a multiverse, it would imply a fourth and grandest Copernican revolution.” Husain in the end seems to agree, quoting Gian Giudice:

Perhaps we need to let go of something we’re holding onto too tightly. Maybe we need to think bigger, refocus, regroup, reframe our questions to nature. The multiverse, he says, could open up “extremely satisfying, gratifying, and mind-opening possibilities.”

Of all the pro-multiverse arguments I heard, this is the one that appeals to me the most. In every scenario, for every physical system, we can pose infinitely many questions. We try to strip a problem back to the essentials and ask the most basic questions, but our intuition is built upon what came before, and it is entirely possible that we are drawing upon paradigms that are no longer relevant for the new realms we are trying to probe.

The multiverse is less like a closed door and more like a key. To me, the word is now tinged with promise and fraught with possibility. It seems no more wasteful than a bower full of roses.

Rees and Husain do a good job of showing that if science is about feelings, then Multiverse fans have a fine argument against critics arguing based on their negative feelings. The problem of course is that science is not about feelings but about evidence. The argument by critics that needs to be addressed is that there is no evidence at all for current multiverse scenarios, and no plausible way of getting any by scientific methods.

Nautilus has another multiverse-related piece just out, We Have Pushed Physics Too Far, by Marcelo Gleiser. My reading of the piece is that Gleiser agrees that the Multiverse is not successful science (“Parallel universes are a non-answer”), and I believe most physicists also agree. Unfortunately the lessons he draws from this (as I’m afraid many others are doing) is that the problem not a particular research program that failed (string theory, by ending up with the string landscape and the multiverse), but the whole idea of pursuing mathematical ideas about further unification:

We can call this the ultimate Platonic dream, the quest for a single simple and broad-ranging theory of physics. Indeed, during the past four decades, the search for such a theory has inspired many of the brightest physicists in the world. But today we are seeing the limits of this Platonic thrust to mathematize nature, due to a lack of experimental validation and several theoretical obstacles—including the possibility of multiple universes and the troubling questions they pose.

Gleiser sees successful physics as “an expression of intellectual humility”, with our current problem that of Icarus, trying to fly too close to the sun. I strongly disagree with him about this, seeing some of the best of physics as an expression of intellectual arrogance, not humility. It is intellectual arrogance that has gotten our understanding of nature as far as it has gone, and it will require intellectual arrogance to go farther. The current problem of theoretical physics is due not the sin of arrogance, but to a somewhat different one, that of refusing to admit error. Multiverse mania is largely about the refusal to admit that string theory unification is a failed idea. Yes, arrogance is one reason for this refusal, and admitting failure takes some humility. But then moving on to find different, more successful ideas will require a lot of both mathematics and intellectual arrogance.

Update: One more article at Nautilus about the multiverse. At least this one is explicitly theology, it explains:

a section of liturgy recited whenever we take the Torah out of the ark, and it’s related to a prayer that many Jews know, “Adon Olam.” The phrase is usually translated as “Sovereign of the Universe,” where the word olam can mean both “the universe” and “eternity,” expressing tremendous expanses of both space and time. But in this particular section of the Torah service, God is called “Adon Olamim,” where the suffix -im makes the word plural. This means that God is “Sovereign of the Universes,” as in, “more than one universe.” God doesn’t need to be a designer who had a specific plan in mind that led to the creation of humanity. God is, in fact, the Sovereign over all the universes, including the ones that don’t have life in them.

Update: Yet more explicit theological coverage of the Multiverse at science magazine Nautilus, with an article from Mary-Jane Rubinstein, a professor of religion, who is interested in multiverse versions of pantheism and explains:

As a professor of religious studies, I am particularly drawn to the places where religion and science seem antagonistic, but turn out to be entwined. The multiverse, I would argue, is one of those places.

My only disagreement here would be whether being a place where science and religion are intertwined is a good or bad thing…

Update: Yet more in the Nautilus series on the Multiverse: more theology, and now teleology.

Update: In case you were worried that Multiverse pseudo-science was incompatible with the Quran, have no fear.

Update: 2017 is well on its way to a bumper crop of Multiverse Mania. Today it’s New Scientist’s turn.

Update: This crap is just endless, more every day. Today it’s at Astronomy Magazine, about this nonsense, debunked long ago by Jennifer Ouellette.

Posted in Multiverse Mania | 73 Comments

What Graduate School in Theoretical Physics is Really Like

Posted on December 29, 2016 by woit

I’m about to head off for a short New Year’s vacation in West Texas, but wanted to recommend a wonderful article that just appeared at Nautilus. It’s a memoir by Bob Henderson (who I met when he wrote about me, see here), appearing under the title What Does Any of This Have To Do with Physics? (although the title of the web-page, What Graduate School in Theoretical Physics is Really Like, is more descriptive).

Henderson was a graduate student at Rochester in theoretical physics, working with S.G. Rajeev. He later went to work on Wall Street, and more recently in journalism. His Nautilus piece is the best explanation I’ve ever seen of what it’s like to start working in this field as a graduate student, should certainly be required reading for anyone thinking of going into the subject. It’s also somewhat of a profile of Rajeev, who has worked on a wide variety of topics in theoretical physics.

One of the main themes of the piece is Henderson’s thinking about how and why he left theoretical physics, why he “quit”. Something to keep in mind is that this kind of decision is what most people who get Ph.Ds in the subject end up facing. There are 5-10 times more people getting Ph.Ds in this field than there are permanent positions doing research in it, so the career path starts out with a game of musical chairs that you are highly likely to lose. Different people make the choice to quit the game and do something else at different points and in different ways.

Henderson does an excellent job also of explaining what the real problem is with doing this kind of research: that of figuring out what the right thing to calculate is. For everyone, but especially for those at the beginning of a career, the subject is a huge collections of topics one doesn’t understand. One has to somehow choose a direction to pursue, and it most likely won’t go anywhere:

Writers talk of the terror of facing a blank page, but it’s no different for theorists like Rajeev trying to choose which path to take. There are an infinite number to choose from, and most go nowhere or back from where you came. The clock is always ticking and you spend so much time in the dark that it can make you not only question your path, but your own self worth. It can make you feel stupid.

Sticking with this and making a career of it involve some combination of good luck (being in the right place at the right time), ability, self-confidence, not having a family to support, and a host of other factors. As Rajeev explains to him:

Without naming names, he ticked through a catalog of his contemporaries who’d succeeded in theoretical physics even without having the towering mathematical intellect that I was sure it took and that Rajeev surely has. They’d made it, Rajeev explained, by focusing on problems that played to their strengths, or by taking advantage of computers, or by collaborating with peers who had complementary skills. Some socially gifted but not so mathematically talented types had gone quite far this way, earned a lot of renown.

Anyway, the whole piece is well-worth reading. Another recently published Nautilus piece that I learned about from a link on this one is The Universes of a Woman in Science. It’s by Kate Marvel, who shares with Henderson (and hundreds if not thousands of others…) the experience of getting a theoretical physics Ph. D. (string cosmology in her case), and then leaving the subject for another field (in her case, climate science, which she blogs about here).

Posted in Uncategorized | 47 Comments