# Tag Archives: graphs

## Graphs on groups, 3

Since this stuff keeps growing, I have decided to keep the most recent version on the web. It is now nearly twice as long as the first version I circulated. If you are interested, please take a copy: it’s at … Continue reading

Posted in Uncategorized | | 2 Comments

## G2D2, 1: setting the scene

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

Posted in exposition, history, Uncategorized | | 1 Comment

## OuLiPo

OuLiPo, or Ouvroir de Littérature Potentielle (which they translate as “Charity bazaar of potential literature”) were a collection of writers I knew little about until yesterday. I knew a couple of things: Martin Gardner wrote about them, mentioning among other … Continue reading

Posted in mathematics and ... | | 3 Comments

## Easy to state, hard to solve?

I described here how Pablo Spiga and I showed that all but finitely many nontrivial switching classes of graphs with primitive automorphism group contain a graph with trivial automorphism group, and found the six exceptions. (The trivial switching classes are … Continue reading

## Solutions

The word “solutions” is much overused, even misused, now. When I see a van with “Cleaning solutions” on the side, I imagine it full of containers of ammonia or soapy water, while “Printing solutions” can only mean ink … But … Continue reading

Posted in books, teaching | | 1 Comment

## Primitive graphs

A primitive graph is one whose automorphism group acts primitively on the vertices: that is, the group is transitive on the vertices, and there is no non-trivial equivalence relation which it preserves. This post is not about why primitive graphs … Continue reading

## The arXiv

It will be absolutely clear to anyone who has given this blog more than a casual glance that I am a dinosaur mired in the 1960s or thereabouts, and quite out of tune with the modern world of Facebook, impact, … Continue reading

Posted in exposition, open problems, the Web | Tagged , , | 4 Comments

## MathOverflow

Today I put a toe into the pool that is MathOverflow for the first time. My question was: Which graphs have the property that the number of i-vertex induced subgraphs is at most i for some i<n/2 (where n is … Continue reading

Posted in doing mathematics, mathematics | | 8 Comments

## Transitivity and synchronization

Let Sn be the symmetric group of all permutations of {1,…,n}, and Tn the full transformation monoid of all functions from this set to itself. Recently I have come to the meta-conjecture that there is a fairly close analogy between … Continue reading