Évènement

Shreya Sharma
Université de Bâle
https://www.shreya-sharma.com/

Date(s) : 26/11/2026   iCal
11h00 - 12h00

Suppose a group acts on a variety. If it preserves a line bundle on the variety, must the action also lift compatibly to the fibers of that line bundle? The answer is not always: there can be a cohomological obstruction. The obstructions arising from all invariant line bundles form the Amitsur group of the action. Remarkably, this group is unchanged under equivariant
birational maps, and therefore, it can be used to distinguish group actions birationally and to obtain obstructions to equivariant versions of rationality and stable rationality. After introducing the invariant through concrete examples, I will discuss its classification in higher dimensions, focusing on toric varieties and smooth Fano threefolds.

Emplacement
I2M Saint-Charles - Salle de séminaire

Catégories

• Séminaire