Category Archives: exposition

a post aimed to teach something

G2D2, 4: the second week

Posted on 04/09/2019 by

The lecturers of the first two minicourses now gave way for the second team. Mike Boyle and Scott Schmieding told us about symbolic dynamics, in particular, subshifts and their automorphism groups. This was particularly valuable to me: I had dove … Continue reading →

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G2D2, 2: first week

Posted on 18/08/2019 by

The campus of the China Three Gorges Hotel has a small river, full of waterlilies and lotus flowers. Beside it runs a main road, along which big water trucks run, shooting atomised water from cannon-like structures; we are told this … Continue reading →

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G2D2, 1: setting the scene

Posted on 12/08/2019 by

I’m in Yichang, at the China Three Gorges University, for the conference and summer school G2D2 (“Groups and graphs, designs and dynamics”). This is the sixth meeting in the series: the previous ones were G2C2: Groups and graphs, cycles and … Continue reading →

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Proper Jordan schemes exist!

Posted on 28/06/2019 by

A new field of research has just been created by Misha Klin, Misha Muzychuk and Sven Reichard: proper Jordan schemes. They answered a question which I posed some time ago (I don’t remember when), about whether such objects exist. I … Continue reading →

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London Combinatorics Colloquia 2019

Posted on 11/05/2019 by

In London last week for the two combinatorics colloquia, at Queen Mary and LSE. The weather was unusually grey and rainy; it seems in retrospect that it is almost always fine and sunny for this event, but I know that … Continue reading →

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Fair games and Artin’s conjecture

Posted on 10/04/2019 by

A few years ago I described Persi Diaconis’ response to G. H. Hardy’s claim that there is a real dividing line between real and recreational mathematics. (See the report here.) This led from Persi’s first experiments in card shuffling to Artin’s conjecture … Continue reading →

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A family of non-synchronizing groups

Posted on 06/01/2019 by

As I explained recently, according to the O’Nan–Scott Theorem, a finite primitive permutation group either preserves a Cartesian structure, or is of affine, diagonal or almost simple type. In all these types except the last, the action of the group … Continue reading →

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