Math News July 20th, 2009
Patrick Stein

An aggregation of some of the math blogs that I follow.

Math News (26 - 50 of about 2984) (xml) (Feedlist)

Happy Birthday Ervin, János, Péter, and Zoli!Gil Kalai
(06.07.2014 13:16h)

The four princes in summit 200, ten years ago. Left to right Ervin Győri, Zoltán Füredi, Péter Frankl and János Pach In 2014, Péter Frankl, Zoltán Füredi, Ervin Győri and János Pach are turning 60 and summit 240 is a conference this week in Budapest to celebrate the birthday of those ever-young combinatorics princes. I know the four guys for about 120 years. I first met Peter and Janos together I think in Paris in 1979, then Zoli at MIT in 1985 and I met Ervin in the mid late 90s in Budapest. Noga Alon have recently made the observation ... [Link]

(05.07.2014 20:53h)

One of the most unfortunate developments of modern football, and a clear symptom of the decline of civilization, is the regrettable irruption in the comments of a deluge of factoids that manage to simultaneously give a bad name to team sports and to statistics “This is the first time in twenty-one competitive games played in the Southern Hemisphere that a French Number 10 player’s backward pass from the left foot has been intercepted by a Dutch player born in Amsterdam” . Roger Couderc certainly did not need this to make a game come to life of course, technically, he was ... [Link]

What makes the Monster Lie Algebra special?Scott Carnahan
(05.07.2014 19:37h)

This is a post I’d been meaning to write for several years, but I was finally prompted to action after talking to some confused physicists. The Monster Lie Algebra, as a Lie algebra, has very little structure – it or rather, its positive subalgebra is quite close to being free on countably infinitely many generators. In addition to its Lie algebra structure, it has a faithful action of the monster simple group by Lie algebra automorphisms. However, the bare fact that the monster acts faithfully on the Lie algebra by diagram automorphisms is not very interesting: the almost-freeness means that ... [Link]

Elsevier in AustraliaScott Morrison
(05.07.2014 19:37h)

I’ve just got back from talking to Roxanne Missingham, the University Librarian here at ANU, about Elsevier, and I want to quickly report on what I learnt. I don’t yet have any of the juicy numbers revealing what libraries are paying for their Elsevier subscriptions as Timothy Gowers has been doing in the UK; if you haven’t read his post do that first! . Nevertheless there are some interesting details. Essentially all the Australian universities, excepting a few tiny private institutes, subscribe to the Freedom collection this is the same bundle that nearly everyone is forced into subscribing to . ... [Link]

The many principles of conservation of numberDavid Speyer
(05.07.2014 19:37h)

In algebraic geometry, we like to make statements like: “two conics meet at points”, “a degree four plane curve has bitangents”, “given four lines in three space, there are lines that meet all of them”. In each of these, we are saying that, as some parameter the conics, the degree four curve, the lines changes, the number of solutions to some equation stays constant. The “principle of conservation of number” refers to various theorems which make this precise. In my experience, students in algebraic geometry tend to pick up the rough idea but remain hazy on the details, most likely ... [Link]

Mathematical Research Community on Cluster Algebras in Utah this summerDavid Speyer
(05.07.2014 19:37h)

This June 8 to 14, there will be a week long gathering in Snowbird, Utah for young mathematicians working on cluster algebras. The target audience here are either current graduate students, or people with Ph. D. in the last 3 or so years, who would be ready to start working on problems in cluster algebras. The hope is to spend a lot of time getting collaborations and projects going during the week. The organizers are Michael Gekhtman, Mark Gross, Gregg Musiker, Gordana Todorov and me. We still have room for a number more applicants, so we would like to encourage ... [Link]

Australian Research Council journal listScott Morrison
(05.07.2014 19:37h)

This post may only be of interest to Australian mathematicians; sorry! Summary: A number of mathematics journals e.g. Quantum Topology, Forum of Mathematics Sigma and Pi, and probably many others , are not listed on the new official journal list in Australia. Please, help identify missing journals, and submit feedback via Every few years the Australian Research Council updates their “official list of journals”. One might wonder why it’s necessary to have such a list, but nevertheless it is there, and it is important that it is accurate because the research outputs of Australian mathematicians are essentially filtered by ... [Link]

Course on categorical actionsBen Webster
(05.07.2014 19:37h)

I have the excellent luck to be sending this semester in Paris, thanks to the Fondation Sciences Mathématiques de Paris. Part of the deal is that I’m giving a weekly course at the “graduate level” though I think I have more professors than graduate students in the course on higher representation theory. Also thanks to FSMP, the course is being videotaped and posted online; the first installment is up here. I’m also posting the videos and additional commentary on a WordPress site; if you have any questions, you can always ask them there or here, but maybe it’s more germane ... [Link]

Postdocs at ANUScott Morrison
(05.07.2014 19:37h)

Tony Licata and I are each now hiring a postdoc at the Mathematical Sciences Institute of the Australian National University. We intend that these will be 2 year positions, with minimal teaching requirements. There is an informal description of the jobs at, including some information about the grants funding these positions. The official ad is online at and you can find it on MathJobs at Please contact us if you have questions, and please encourage good Ph.D. students especially with interests in subfactors, fusion categories, categorification, or related subjects to apply! [Link]

Mathematics Literature Project progressScott Morrison
(05.07.2014 19:37h)

We’ve made some good progress over at the Mathematics Literature Project. In particular, we’ve completely analyzed the 2013 issues of five journals: Adv. Math. Algebr. Geom. Topol. Ann. of Math. 2 Discrete Math. Geom. Funct. Anal. The colour coded bars show the fractions of papers available on the arXiv, available on authors’ webpages, and not freely accessible at all; these now appear all over the wiki, but unfortunately don’t update automatically. Over at the wiki you can hover over these bars to get the numerical totals, too. Thanks everyone for your contributions so far! If you’ve just arrived, check out ... [Link]

An editable database tracking freely accessible mathematics literature.Scott Morrison
(05.07.2014 19:37h)

This post continues a discussion started by Tim Gowers on google+. [1] [2] For the impatient, go visit, or for the really impatient 2013 . It would be nice to know how much of the mathematical literature is freely accessible. Here by ‘freely accessible’ I mean “there is a URL which, in any browser anywhere in the world, resolves to the contents of the article”. And my intention throughout is that this article is legitimately hosted, either on the arxiv, on an institutional repository, or on an author’s webpage, but I don’t care how the article is actually ... [Link]

From the drawers of the museumNoah Snyder
(05.07.2014 19:37h)

One of my amateur interests is paleontology. Paleontologists looking for new examples have two options: go out in the field and dig up a new example, or go looking through drawers of museums to find old examples that had been overlooked. In this blog post I want to give an interesting example of the latter kind of research being useful in mathematics. Namely in discussions with Zhengwei Liu, we realized that an old example of Ocneanu’s gives an answer to a question that was thought to be open. One of the central problems in fusion categories is to determine to ... [Link]

My First Conscious PaperletThe Power of the Digi-Comp II
(04.07.2014 14:46h)

Foreword: Right now, I have a painfully-large stack of unwritten research papers. Many of these are “paperlets”: cool things I noticed that I want to tell people about, but that would require a lot more development before they became competitive for any major theoretical computer science conference. And what with the baby, I simply don’t have time anymore for the kind of obsessive, single-minded, all-nighter-filled effort needed to bulk my paperlets up. So starting today, I’m going to try turning some of my paperlets into blog posts. I don’t mean advertisements or sneak previews for papers, but replacements for papers: ... [Link]

My Mathematical Dialogue with Jürgen EckhoffGil Kalai
(03.07.2014 21:25h)

Jürgen Eckhoff, Ascona 1999 Jürgen Eckhoff is a German mathematician working in the areas of convexity and combinatorics. Our mathematical paths have met a remarkable number of times. We also met quite a few times in person since our first meeting in Oberwolfach in 1982. Here is a description of my mathematical dialogue with Jürgen Eckhoff: Summary 1 1980 we found independently two proofs for the same conjecture; 2 1982 I solved Eckhoff’s Conjecture; 3 Jurgen 1988 solved my conjecture; 4 We made the same conjecture around 1990 that Andy Frohmader solved in 2007, and finally 5 Around 2007 We ... [Link]

The Linearity of TracesThe n-Category Café
(01.07.2014 05:05h)

At long last, the following two papers are up: Kate Ponto and Mike Shulman, The linearity of traces in monoidal categories and bicategories Kate Ponto and Mike Shulman, The linearity of fixed-point invariants I’m super excited about these, and not just because I like the results. Firstly, these papers are sort of a culmination of a project that began around 2006 and formed a large part of my thesis. Secondly, this project is an excellent “success story” for a methodology of “applied category theory”: taking seriously the structure that we see in another branch of mathematics, but studying it using ... [Link]

How Many Women?Test Your Intuition 23
(29.06.2014 18:43h)

How many women can you find on this poster announcing the 25th Jerusalem School in Economics Theory devoted to Matching and Market Design? Please respond to the poll: Take Our Poll function d,c,j {if !d.getElementById j {var pd=d.createElement c ,s;;pd.src=' c [0];s.parentNode.insertBefore pd,s ;} else if typeof jQuery !=='undefined' jQuery d.body .trigger 'pd-script-load' ;} document,'script','pd-pollda~ ; [Link]

ECM2016 — your chance to influence the programmegowers
(29.06.2014 16:50h)

UPDATE: I HAVE NOW GONE BACK TO MODERATING COMMENTS ONLY IF THEY ARE FROM PEOPLE WHO HAVE NOT HAD A COMMENT ACCEPTED IN THE PAST. SO IF YOU HAVE A SUGGESTION TO MAKE FOR AN ECM2016 SPEAKER, PLEASE EMAIL A MEMBER OF THE COMMITTEE DIRECTLY RATHER THAN COMMENTING HERE. Just before I start this post, let me say that I do still intend to write a couple of follow-up posts to my previous one about journal prices. But I’ve been busy with a number of other things, so it may still take a little while. This post is about the ... [Link]

Kan Extension Seminar Talks at CT2014The n-Category Café
(28.06.2014 01:26h)

The International Category Theory Conference will take place this coming week, Sunday June 29 - Saturday July 4th, in old Cambridge. To those readers who will be in attendance, I hope you’ll stop by to visit the Kan Extension Seminar, which will present a series of eight 15-minute expository talks this coming Sunday June 29 at Winstanley Lecture Theatre in Trinity College. We will have tea starting at 2pm with the first talks to commence at 2:30. There will be a short break around 3:50pm with the second series of talks to begin at 4:10. The talks should finish around ... [Link]

Enriched Indexed Categories, AgainThe n-Category Café
(27.06.2014 18:54h)

Guest post by Joe Hannon. As the final installment of the Kan extension seminar, I’d like to take a moment to thank our organizer Emily, for giving all of us this wonderful opportunity. I’d like to thank the other participants, who have humbled me with their knowledge and enthusiasm for category theory and mathematics. And I’d like to thank the nCafé community for hosting us. For the final paper of the seminar, we’ll be discussing Mike Shulman’s Enriched Indexed categories. The promise of the paper is a formalism which generalizes ordinary categories and can specialize to enriched categories, internal categories, ... [Link]

Happy Birthday Richard Stanley!Gil Kalai
(27.06.2014 15:19h)

This week we are celebrating in Cambridge MA , and elsewhere in the world, Richard Stanley’s birthday. For the last forty years, Richard has been one of the very few leading mathematicians in the area of combinatorics, and he found deep, profound, and fruitful links between combinatorics and other areas of mathematics. His works enriched and influenced combinatorics as well as other areas of mathematics, and, in my opinion, combinatorics matured greatly as a mathematical discipline thanks to his work. Trivia Quiz Correct or incorrect? 1 Richard drove cross-country at least 8 times 2 In his youth, at a wild ... [Link]

A Physically Universal Cellular AutomatonScott
(26.06.2014 21:50h)

It’s been understood for decades that, if you take a simple discrete rule—say, a cellular automaton like Conway’s Game of Life—and iterate it over and over, you can very easily get the capacity for universal computation. In other words, your cellular automaton becomes able to implement any desired sequence of AND, OR, and NOT gates, store and retrieve bits in a memory, and even in principle run Windows or Linux, albeit probably veerrryyy sloowwllyyy, using a complicated contraption of thousands or millions of cells to represent each bit of the desired computation. If I’m not mistaken, a guy named Wolfram ... [Link]

Bourbaki seminar onlineKowalski
(26.06.2014 09:42h)

Whenever I can, I like to attend the Bourbaki Seminar in Paris, but that’s not always feasible. June 2014 Of course, even without being present, the written text of the seminar is always available later to learn what the talks were about. But, especially when the subject is not close to something I know, it’s often much better to have seen first a one-hour presentation which distills the most important information, which may well be a bit hidden in the written text for non-specialists. So it is rather wonderful to see that, since last March, the lectures of the Bourbaki ... [Link]

Lebesgue measure as the invariant factor of Loeb measureTerence Tao
(26.06.2014 04:07h)

There are a number of ways to construct the real numbers , for instance as the metric completion of thus, is defined as the set of Cauchy sequences of rationals, modulo Cauchy equivalence ; as the space of Dedekind cuts on the rationals ; as the space of quasimorphisms on the integers, quotiented by bounded functions. I believe this construction first appears in this paper of Street, who credits the idea to Schanuel, though the germ of this construction arguably goes all the way back to Eudoxus. There is also a fourth family of constructions that proceeds via nonstandard analysis, ... [Link]

Influence, Threshold, and NoiseGil Kalai
(25.06.2014 23:00h)

My dear friend Itai Benjamini told me that he won’t be able to make it to my Tuesday talk on influence, threshold, and noise, and asked if I already have the slides. So it occurred to me that perhaps I can practice the lecture on you, my readers, not just with the slides here they are but also roughly what I plan to say, some additional info, and some pedagogical hesitations. Of course, remarks can be very helpful. I can also briefly report that there are plenty of exciting things happening around that I would love to report about – ... [Link]

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