This Thursday Jean-Yves Welschenger will speak in Imperial about Welschenger invariants. He will give a one hour lecture at 1 pm, room 340. Afterwards we could have an informal discussion.

Abstract: “Several years ago, I introduced an invariant under deformation of real symplectic four-manifolds, that is symplectic four-manifolds equipped with an antisymplectic involution. For every generic almost complex structure J which is tamed by the symplectic form and makes the involution anti J-holomorphic, this invariant bounds from below the number of real rational J-holomophic curves (curves invariant under the involution) in a given homology class and passing through a given collection of points. After recalling the construction of this invariant, I will explain why these lower bounds are sometimes sharp.”