Résume | A lot of recent research has sprung out of work towards a conjecture of Guralnick: There is a constant $c$ such that for any finite group $G$ and irreducible, faithful representation $V$ for $G$, the dimension of $H^1(G,V)$ is less than $c$. This conjecture reduces to the case of simple groups. New computer calculations of F. Luebeck and a student of L. Scott show that it is likely that the conjecture is wrong, but if one fixes either the dimension of $V$ or the Lie rank of $G$ then there do exist bounds, due to Parshall--Scott (defining characteristic) and Guralnick--Tiep (cross characteristic). The latter is explicit and the former has now been made explicit by some recent work of A. Parker and myself. There are many more general results, however. I'll give an overview of the area. |