Category Archives: symmetric group

one of my favourite mathematical objects

Au revoir, GRA

Posted on 18/03/2020 by

Today (Wednesday 18 March) the Groups, Representations and Applicatons programme at the Isaac Newton Institute came to a premature end. There are still some hopes that it can be revived later, but at the moment the only certainty is that … 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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Chains of semigroups

Posted on 27/01/2015 by

I have written here about the lovely formula for the length of the longest chain of subgroups in the symmetric group Sn: take n, increase it by 50% (rounding up if necessary), subtract the number of ones in the base … Continue reading →

Posted in exposition, open problems, symmetric group | Tagged , , , , , , | 7 Comments

Remoteness

Posted on 11/10/2011 by

After the last bit of bureaucratic nonsense, what a relief to turn to mathematics again. Maximilien Gadouleau and I have just submitted a paper about a concept for finite metric spaces somewhat related to domination, which we call remoteness. It … Continue reading →

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The symmetric group, 12

Posted on 21/04/2011 by

This instalment is about the maximal subgroups of the symmetric group, and the O’Nan–Scott Theorem. There are two versions of this theorem, one of which is sometimes called the Aschbacher–O’Nan–Scott Theorem. One is about maximal subgroups of the symmetric group … Continue reading →

Posted in exposition, symmetric group | Tagged , , , | 6 Comments

The symmetric group, 11

Posted on 09/04/2011 by

I am going to talk about a celebrated theorem of John Dixon and some of its variants; this is on my mind at the moment, for reasons I will explain at the end. Dixon’s theorem is easily stated. Two random … Continue reading →

Posted in exposition, symmetric group, synchronization | Tagged , , | 4 Comments

The symmetric group, 9

Posted on 18/01/2011 by

There are many different ways to regard a finite symmetric group as a metric space. These have been used for various purposes. Here I would like to say something about them. One application of such metrics is in non-parametric statistics. … Continue reading →

Posted in exposition, mathematics, symmetric group | 1 Comment