The study of Lagrangian submanifolds is a central theme in symplectic geometry. In this talk, we are going to study Lagrangian submanifolds in S² x S², equipped with standard symplectic forms. Our goal is to understand which symplectic forms on S² x S² carry Lagrangian Klein bottles.

First, we will focus on constructing the Klein bottles, using certain techniques from the theory of Lagrangian torus fibrations. This theory effectively reduces many constructive problems into problems of classical affine geometry of the plane.

Afterwards, I will explain how to obstruct the existence of some Lagrangian Klein bottles, using pseudoholomorphic curve techniques. Together, the obstructive part and the constructive part completely determine which symplectic forms in S² x S² carry a Lagrangian Klein bottle.

This is joint work with J. Evans and work in progress with Evans, J. Hauber, J. Schmitz.

[Attention au changement de jour (mercredi et non jeudi) exceptionnel.]