Symplectic geometry of rationally connected threefolds

Abstract

We study the symplectic geometry of rationally connected 3-folds. The first result shows that rational connectedness is a symplectic deformation invariant in dimension 3. If a rationally connected 3-fold X is Fano or has Picard number 2, we prove that there is a non-zero Gromov-Witten invariant with two insertions being the class of a point. Finally we prove that many other rationally connected 3-folds have birational models admitting a non-zero Gromov-Witten invariant with two point insertions.