High Frobenius pushforwards generate the bounded derived category

Abstract

This work concerns generators for the bounded derived category of coherent sheaves over a noetherian scheme $X$ of prime characteristic. The main result is that when the Frobenius map on $X$ is finite, for any compact generator $G$ of $\mathsf{D}(X)$ the Frobenius pushforward $F_{\ast }^{e}G$ generates the bounded derived category whenever $p^e$ is larger than the codepth of $X$, an invariant that is a measure of the singularity of $X$. The conclusion holds for all positive integers $e$ when $X$ is locally complete intersection. The question of when one can take $G={\mathcal{O}}_X$ is also investigated. For smooth projective complete intersections it reduces to a question of generation of the Kuznetsov component.

32 pages; minor revision. To appear in Forum of Mathematics, Sigma