Tag Archives: oligomorphic permutation groups

A counting problem

I quite often get questions by email. Mostly I can’t answer them, but sometimes I can, and sometimes the answers might be of more general interest. Suppose that we have m boxes and a supply of identical balls. In how … Continue reading

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A crash course on group theory

I have just finished a crash course on group theory at Universidade de Lisboa. The notes are here. From the preface: On a visit to Universidade de Lisboa in November 2016, I was asked to give a “crash course” in … Continue reading

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Banff, day 1

The first day of the meeting is over. We met in the well-appointed lecture room at BIRS, on the Banff Centre campus, with its comfortable seating: We have also had the group photo taken: The first day was devoted to … Continue reading

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Categorification, step 1

Today at the St Petersburg meeting, Igor Frenkel talked about categorification. He explained that there are five levels (maybe more!) and one has to take certain steps between them; he illustrated with an example, where level 0 was Jacobi’s Triple … Continue reading

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The title of this post is half-serious: it is designed to catch attention, but I think there are interesting things lurking here which deserve more exploration. Species A species describes a class of objects built on finite sets, in a … Continue reading

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