CEMAT

The ADE affair

Por Peter J. Cameron (Univ. St Andrews e CEMAT).

Abstract: The Coxeter--Dynkin diagrams of type ADE occur in so many different parts of mathematics, from singularity theory to mathematical physics to graph theory, that they surely play a very deep role in our subject. In the present century, they have occurred in the theory of cluster algebras by Fomin and Zelevinsky, and a constructive version of the McKay correspondence has been found by Dechant. The talk will discuss some of these connections.

Difference hierarchies

Por Jean-Éric Pin (Institut de Recherche en Informatique Fondamentale, CNRS et University Paris-Diderot).

Abstract: Difference hierarchies were originally introduced by Hausdorff and they play an important role in descriptive set theory. In this lecture, I will review standard techniques on difference hierarchies, mostly due to Hausdorff. These techniques will be illustrated by some decidability results on difference hierarchies based on shuffle ideals and polynomials of group languages.

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