Category Archives: Combinatorics

Map of the world

At least as far as families of reflection groups with nice combinatorics are concerned

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“Magical Mathematics” by Persi Diaconis and Ron Graham

This was a gift from my wonderful friend AHM, following the death of Graham last year. I enjoyed it quite a lot, but it’s also very weird. For example, chapters bounce around dramatically in tone and content (some are about … Continue reading

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“Mathematical education” by G. St. L. Carson

This is the other book I mentioned finding at the Book Barn.  It is a collection of eight lectures delivered by the author in 1912 and 1913, and a fascinating historical document.  Some features that I found particularly interesting follow. … Continue reading

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Finding the magic coins

I’ve been reading through Daniel Velleman and Stan Wagon’s puzzle book Bicycle or Unicycle? and generally enjoying it – the puzzles include simple variations on classics, clever things I haven’t seen before, and some nontrivial uses of real mathematical thinking … Continue reading

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Jargon

This tickled my fancy: For all the other parameters, has no real structure. [R. Corran, E.-K. Lee, S.-J. Lee, Braid groups of imprimitive complex reflection groups, J. Algebra, 2015] (No, it’s not floppy — it’s a complex reflection group. Here … Continue reading

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Factor triples

Over at JD2718, Jonathan asks the following question: [A conference] presenter posed a problem that required finding three numbers that multiplied to make 72. The list included 1, 8, 9 and 2, 2, 18 and 3, 4, 6 and several … Continue reading

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Open problems in algebraic combinatorics

This is pretty cool: Open Problems in Algebraic Combinatorics blog.  (It’s attached to this conference.)

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Coincidences among small groups

I like to study reflection groups of various kinds.  Let Sn denote the group of permutations of n points, let GL(n, q) denote the general linear group of invertible linear transformations of an n-dimensional vector space over the finite field with … Continue reading

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Herstmonceux

As I mentioned, after Vancouver I went to a conference at Herstmonceux Castle in Sussex, England.  It was mathematically excellent, and I feel that BBC detective shows properly prepared me for my first visit to the UK.  Trees in England … Continue reading

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The Erdős FBI file

A cute little article here about Paul Erdős’s FBI file.  The short version is … that it’s not very interesting; the FBI routinely (and correctly) determined that he was just interested in doing mathematics.  In a Minnesota-centric note, it was … Continue reading

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