Algebra Seminar

In 1961, Jan-Erik Roos published a theorem about the derived functors of the limit. We will begin by discussing the theorem, its background, and its significance.

Then we will give a counterexample to Roos' 1961 theorem. This amounts to constructing a certain abelian category with strange behavior. Finally, we will discuss the background which led to this strange abelian category, and how the study of similar abelian categories leads to new structure theorems for triangulated categories.