Following Emily’s advice, I recently signed up to be mentor in the AWM Mentor Network. It’s been pretty good thus far (I recommend it to any of you who would like to do some menting), but I got a request from my mentee that I thoug...

The past few weeks there has been a summer school and conference on geometric representation theory and extended affine Lie algebras at University of Ottawa. As part of this event, I gave a week long lecture series entitled “three ...

In supermarkets in Zürich (and in other German-speaking parts of the world), aluminium foil is called “Aluminiumfolie” — fairly straightforward, certainly, but since the word “folie” means “madness” in French, every time I see this ...

The FOCS list is out, (with abstracts). 73 papers accepted. Some papers that popped up on my radar screen (post more in the comments since I'll probably miss many good ones):Matt Gibson and Kasturi Varadarajan. Decomposing Coverings...

(this is part of an occasional series of essays on clustering: for all posts in this topic, click here)k-means (also known as Lloyd's algorithm) is probably the most well known clustering algorithm, and as such, deserves some discus...

It’s taken me a while to write this up, since I’ve been in the process of moving house – packing and unpacking and all the rest. However, a bit over a week ago, I was in Montreal, attending MakkaiFest ‘09 at the Centre de Recherch...

I recently read a charming little paper: Quasi-elliptic integrals and periodic continued fractions, by van der Poorten and Tran. Most of us who have taken a number theory course of some kind learned how to solve Pell’s equation: wh...

n-Café regulars will know about Representative Conyer's bill that would repeal the National Institute of Health's public access policy and forbid other US funding agencies from mandating open access to research papers written with t...

Elsevier offered gift certificates to academics to write 5-star reviews of a book on Amazon and Barnes & Noble.

a few questions:1. given a measurable set E (in R) with finite (lebesgue) measure, and any 0 < a < 1, there exists a subset A of E such that m(A) = am(E). i know this is true for a = 1/2, but how about all a in (0, 1)?2. this one i...

We continue discussing Dirac notation by bringing up the inner product. To this point, our notation applies to any vector space and its dual, with the ket denoting a vector and the bra denoting a linear functional . The evaluat...

Martin Laubinger studies Lie algebras of groups with generalized smooth manifold structure: Froelicher groups.

Can an accounting tool find fraud in Iran?

Springer Verlag has published a book purporting to give elementary proofs of Fermat's Last Theorem and Goldbach's Conjecture.

Recent news and notes related to prior Numbers Guy columns and blog posts.

There’s a really neat notation for inner product spaces invented by Paul Dirac that physicists use all the time. It really brings to the fore the way a both slots of the inner product enter on an equal footing. First, we have a bra...

I’ve just uploaded a paper to the arXiv, Man and machine thinking about the smooth 4-dimensional Poincaré conjecture, joint with Michael Freedman, Robert Gompf, and Kevin Walker. The smooth 4-dimensional Poincaré conjecture (SPC4) i...

Remember: abstracts are due today at 5pm ET. ...

Okay, everybody in the world now knows that Michael Jackson died. And yes, it’s a big deal. But there’s a lot of reputation-burnishing going on out there, one piece of which I’d like to talk about today. Everyone talks about the m...

I need to prepare a talk on tensor algebra, so I am trying to refresh my memory about that... I have a question about the conditions (as explicit as possible) when a tensor A can be decomposed into a product of two tensors of lesser...