Konstantin Jakob (TU Darmstadt) is speaking in the Algebra Seminar this week. We will go out for lunch after the talk. When: Friday, 10 November, 12-1pm Where: Carslaw 173 Title: A Deligne-Simpson problem for irregular G-connections over P^1 Abstract: The Deligne-Simpson problem asks for a criterion for the existence of a connection on a punctured P^1 with prescribed singularities. I will explain joint work with Zhiwei Yun on a generalization of this problem for G-connections on P^1 with two singularities, only one of which is a regular singularity, where G is any complex reductive group. We give a geometric and a representation-theoretic existence criterion, and use them to solve the Deligne-Simpson problem in many cases.