Minimal atlases of closed symplectic manifolds
  We study the number of Darboux charts needed to cover a closed connected symplectic manifold $(M,\omega)$, and effectively estimate this number from below and from above in terms of the Lusternik--Schnirelmann category of $M$ and the Gromov width of $(M,\omega)$. 
Yuli Rudyak and Felix Schlenk