Friday, 14 November
01:15 pm
Bielefeld University U2-232
Torsion and complete dualizable objects in tt-categories with a Noetherian ring action
Speaker: Jan Stovicek
Seminar Representation Theory of Algebras
The main object of interest in this talk is a rigidly compactly generated tensor triangulated category with an action of a graded commutative Noetherian ring R making (graded) homomorphism groups between compacts finitely generated R-modules. There are various examples of this setup coming from commutative algebra, modular representation theory of groups or homotopy theory. In joint work with Jun Maillard, we studied the categories of dualizable objects inside the mutually equivalent categories of a-torsion and a-complete objects with respect to a homogeneous ideal a of R. This is a surprisingly well behaved setup. For example, the categories of a-torsion/complete dualizable objects are always Hom-finite over the a-adic completion of R and we can recover them using a form of Cauchy completions from the categories of a-torsion/comlete compact objects. The best results are achieved when we in addition assume that the category of compact objects is strongly generated (or equivalently, has finite Rouquier dimension). Then so is the category of a-torsion/complete dualizable objects and the so-called local regularity condition introduced by Benson, Iyengar, Krause and Pevtsova is automatically satisfied. Moreover, there are Brown representability results providing a "perfect pairing" between the categories of a-torsion/complete compact objects and a-torsion/complete dualizable objects which are formally very similar to Neeman's arXiv:1804.02240.
Next week
There are no announced talks next week.
Further Talks
Thursday, 27 November
04:15 pm
Bielefeld University V2-210/216
Zeros of S-characters - Showcasing the Computer Algebra System OSCAR
Speaker: Michael Joswig
Mathematisches Kolloquium (TRR 358)
The concept of $S$-characters of finite groups was introduced by Zhmud' (1995) as a generalization of transitive permutation characters. Any non-trivial $S$-character takes a zero value on some group element. By a deep result depending on the classification of finite simple groups a non-trivial transitive permutation character even vanishes on some element of prime power order. J-P. Serre asked whether this generalizes to $S$-characters. We provide a translation of this question into the language of polyhedral geometry and thereby construct many counterexamples, using the capabilities of the computer algebra system OSCAR. The work on S-characters is joint with Thomas Breuer und Gunter Malle. OSCAR is joint work with The OSCAR Development Team, currently lead jointly with Simon Brandhorst, Claus Fieker, Tommy Hofmann and Max Horn