Seminarium KMMF "Teoria Dwoistości"

Most of mathematical structures have products whose definitions are considered as "straightforward", and in many cases one does not even think of these definitions as being instances of the categorical one, introduced by Saunders Mac Lane almost sixty years ago. This talk is devoted to a very different story of semidirect products, where the result "every split epimorphism in a nice category is a semidirect product projection" requires a highly non-trivial categorical approach.