Frédéric Déglise

Motives and motivic homotopy

Open Problems Seminar

Seminar SLMath
program Motivic Homotopy Theory: Connections and Applications
Fall 2026
________

Schedule: Friday, 11:00 AM–12:00 PM
Location: Eisenbud Auditorium, SLMath
Organizers: F. Déglise, A. Kundu

Overview: This is an open seminar on open problems of any kind related to motivic homotopy theory. Its aim is to stimulate questions and discussions, and also to inform.

Seminar Schedule:

09/25 Frédéric Déglise Motivic Dimension of Fields A theorem of Borel says, in a suitable sense, that the rational K-theory of a number field lives in just one cohomological degree. A classical calculation of Bass and Tate suggests that adjoining a transcendental variable creates exactly one more.
This raises a deceptively simple question: for a finitely generated field, how many motivic cohomological degrees can there be?
I will explain how generic motives make the pattern particularly transparent, why the nonzero groups can nevertheless be enormous, and how the resulting open problem is related to the conjectural t-structure on mixed motives. At the end, curves and their Jacobians will suggest a broader version of the question.
SLMath announcement
10/02 Andrei Lavrenov Classification Problems for Quadratic Forms and Progress via Motivic Methods I will discuss the classification of quadratic forms of given height and degree, a program initiated by Manfred Knebusch, focusing on quadratic forms of height two and on the conjectural classification proposed by Bruno Kahn, as well as several related conjectures and questions. I will survey what is currently known and explain how Vishik used motivic decompositions of projective quadrics to obtain information about the possible dimensions of height two forms. Finally, I will mention some recent joint work related to these questions.
10/16 Utsav Choudhury Comparison of Nori type motivic categories The talk will present constructions of different Nori type motivic categories, review their known properties, and discuss conjectures and open questions concerning these categories. SLMath announcement
10/30 Haoyang Liu TBA
11/06 TBA
11/13 TBA
11/20 TBA
11/27 TBA
12/04 TBA
12/11 TBA
12/18 TBA
Date Speaker Title Summary Notes