On derived categories of nonminimal Enriques surfaces
  By Orlov's formula, the derived category of blow up must contain the original variety as a semiorthogonal component. This arises an interesting question: does there exist a variety $X$ such that $\operatorname{D}^{\sf b}(X)$ does not admit an exceptional collection of maximal length, but $\operatorname{D}^{\sf b}(\operatorname{Bl}_{x} X)$ admits such a collection? We give such an example where $X$ is a minimal Enriques surface. 
Yonghwa Cho
math.AG