Seminars in Algebra (Spring 2026)

Wednesday, 23rd of September, 2026, at 14:15 in room 656

Speaker: David A. Jorgensen (University of Texas at Arlington)

Title: TBA

Abstract: TBA

Wednesday, 30th of September, 2026, at 15:15 in room 656

Speaker: Peder Thompson (Mälardalen University)

Title: TBA

Abstract: TBA

Wednesday, 7th of October, 2026, at 15:15 in room 656

Speaker: Iacopo Nonis

Title: TBA

Abstract: TBA

Tuesday, 9th of June, 2026, at 14:15 in room 656

Speaker: Hannes Kristinn Árnason (NTNU)

Title: Resolving subcategories in higher AR-theory

Abstract: As a d-cluster tilting subcategory M of an abelian category is known to be d-abelian, one can try to understand it through its d-extension closed subcategories. While higher torsion classes and higher wide subcategories have been studied successfully, d-extension closure is hard to work with on its own. Recent results by Kvamme suggest an alternative characterisation of subcategories of M which are both d-extension closed and generating. Working from this, we look at higher resolving subcategories, proving some of their basic properties as well as a correspondence relating them to cotilting modules inside M.

Thursday, 4th of June, 2026, at 14:15 in room 656

Speaker: Marina Godinho (University of Glasgow)

Title: New Derived Symmetries For Gorenstein Orders

Abstract: A ring morphism p:A→B satisfying certain mild assumptions induces a derived endomorphism of A and a derived endomorphism of B, which are closely related. In fact, the derived endomorphism of A is the twist around the derived restriction of scalars functor, and the derived endomorphism of B is the corresponding cotwist. I will discuss settings in which these endomorphisms are derived equivalences and use this technology to construct new derived autoequivalences of Gorenstein orders. We will end the talk with a very explicit example.

Tuesday, 26th of May, 2026, at 14:15 in room 656

Speaker: Marvin Plogmann (Universität zu Köln)

Title: Recognising Ext-algebras of simple objects

Abstract: An abelian length category can often be recovered from the derived endomorphism algebra of its simple objects. This leads to the following recognition problem: which dg algebras arise in this way?

In this talk, I will describe a characterization for module categories and certain abelian length categories. The key condition is that the associated simple-minded collection is 0-complicial, in the sense of Lurie.

Tuesday, 12th of May, 2026, at 14:15 in room 656

Speaker: Sarah Witherspoon (Texas A&M University)

Title: Cohomological finite generation conjecture

Abstract: Finite dimensional Hopf algebras, and more generally finite tensor categories, have cohomology rings that are graded commutative and are conjectured to be finitely generated. Those for which the conjecture holds come thus equipped with a good theory of support varieties, a geometric approach to understanding modules or objects in the tensor categories. In this talk, we will discuss some categories for which the conjecture has been proven and some for which it has not. We will focus on recent and ongoing research on the finite dimensional pointed Hopf algebras that include small quantum groups.

Tuesday, 28th of April, 2026, at 14:15 in room 656

Speaker: Johanne Haugland (NTNU)

Title: Maximal almost rigid subcategories of the derived category of a gentle algebra

Abstract: To any gentle algebra, one can associate a marked surface with a dissection giving a geometric model for the bounded derived category. In this model, arcs correspond to indecomposable objects and morphisms correspond to intersections of arcs. Inspired by the notion of maximal almost rigid modules, we introduce maximal almost rigid subcategories of the derived category of a gentle algebra and show that these subcategories are in bijection with triangulations of the associated surface. Time-permitting, we discuss mutation of maximal almost rigid subcategories and explain how mutation can be described in terms of flipping of arcs in the associated triangulation.

The talk is based on joint work in progress with Karin M. Jacobsen, Ralf Schiffler and Sibylle Schroll.

Tuesday, 27th of January, 2026, at 14:15 in room 656

Speaker: David Nkansah (NTNU)

Title: Homological algebra without grading

Abstract: Complexes are central objects in homological algebra, and as such, grading is very present within the subject. But what if we discard the grading of a complex? This leads us to the notion of a differential module. In this talk, we explore how the homological algebra of differential modules can detect the finiteness of the injective dimension of a finitely generated module over a local commutative noetherian ring. As an application, we give a new characterisation of when such a ring is Cohen–Macaulay.