Date de l'exposé : 12 janvier 2007
Superimposed codes and related problemsA family of subsets is r-cover-free, if no set is covered by the union of r others. These families were introduced in coding theory by Kautz and Singleton (disjunctive codes, superimposed codes) in early sixties. Variants of these codes were later investigated by Erdos, Frankl and Furedi, Alon and Asodi, Szegedy and Vishvanathan, just to mention a few. These codes are useful in circuit complexity, mobile computing, in the theory of multiple access channels and many other branches of mathematics and computer science. Moreover, they led to the first counter-example for an old conjecture of Grunbaum on point sets in R^n without obtuse triangles.
In this talk we will discuss old and new results on bounds of these codes and their relevance in computer science and pure mathematics.