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Category Archives: Combinatorics
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
Posted in Combinatorics, Math
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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
Open problems in algebraic combinatorics
This is pretty cool: Open Problems in Algebraic Combinatorics blog. (It’s attached to this conference.)
Posted in Academia, Combinatorics, Math
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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 ndimensional vector space over the finite field with … Continue reading
Posted in Combinatorics, Math
Tagged finite field, general linear group, group theory, permutations, symmetric group
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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
Posted in Academia, Combinatorics, Math, Trees
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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 Minnesotacentric note, it was … Continue reading
Posted in Combinatorics, Math, What's the news?
Tagged combinatorics, congress, FBI, Math humor, Minnesota, Paul Erdos
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Proof by induction
If you’re solving a combinatorial problem depending on a parameter n and the first few values are 1, 1, 2, 5, 14, your sequence is the Catalan numbers. If the next term of the sequence is 42, that constitutes a … Continue reading
“My brain is open” by Bruce Schechter
My Brain Is Open is one of two biographies of Paul Erdős that I know of, the other being Hoffman’s The Man Who Loved Only Numbers. I mostly enjoyed this one; it conveyed a good sense of the subject’s eccentricities … Continue reading
Ken Appel has died
The Times has a very nice obituary of Kenneth Appel, the main mastermind behind the proof of the fourcolor theorem, one of the crowning achievements of graph theory. He also sounds likfair pleasant, interesting man. The advent of computers has … Continue reading
Posted in Combinatorics, What's the news?
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