Tag Archives: root systems

The ADE affair, 6

Earlier this semester, we had a beautiful seminar by Pierre-Philippe Dechant, whose work has thrown some entirely new light on this beautiful work of art. I would like to explain a bit about this here. For more details, see his … Continue reading

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Advanced Combinatorics: the St Andrews lectures

Three years ago, when I joined the School of Mathematics and Statistics at the University of St Andrews, it was suggested that I might like to give a final year MMath module on “Advanced Combinatorics”. No compulsion. Well, of course … Continue reading

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An LMS meeting

Last Friday I went to the London Mathematical Society general meeting, at the BMA building in Tavistock Square. On a beautiful warm day I walked along the Regents Canal to Islington and then down through back streets past the former … Continue reading

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G. C. Steward lectures 2008

While I was uploading lecture notes, I also put on the page the notes from my G. C. Steward lectures at Gonville and Caius College in 2008. You can find them here. I spent the first half of 2008 in … Continue reading

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Precursors

Jorge Luis Borges is one of the most mathematical of great writers. In an essay entitled “Kafka and his Precursors”, he pointed out that there is a strange collection of pieces and fragments, including Zeno’s paradox and stories by Han … Continue reading

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The ADE affair, 5

A root system is a finite set S of vectors in Euclidean space with the properties If s,λs∈S, then λ=±1. The set S is mapped to itself by the reflection in the hyperplane perpendicular to each element s of S. … Continue reading

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The ADE affair, 4

Here is a cautionary tale to show that not everything that looks like an instance of the ADE classification actually is so. When I first learned about optimal design in statistics, I was very excited to find that there are … Continue reading

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