The relation between birational geometry and C*-actions

“Doc in Progress” is pleased to introduce you to:

• Lorenzo Barban - PhD in Mathematics - University of Trento

In this friendly talk we explain how birational transformations arise naturally in the context of C*-actions on projective varieties. With the help of examples, we first review basic notions about algebraic torus actions, explaining for instance the Bialynicki-Birula decomposition. We then concentrate on the geometric quotients of a C*-action, explaining how they are all birational to each other. We conclude by asking the opposite question: under which conditions two birationally equivalent varieties can be realized as geometric quotients by a C*-action?