Skip to main content
1 of 8
Martin Brandenburg
  • 63.1k
  • 13
  • 207
  • 424

Description of quasi-coherent modules on a product

Let $R$ be a ring and $X,Y$ two $R$-schemes, which you may assume to be noetherian or anything reasonable you like. Is it possible to "construct" $\text{Qcoh}(X \times_R Y)$ out of $\text{Qcoh}(X)$ and $\text{Qcoh}(X)$ in the $2$-category of all cocomplete $R$-linear tensor categories?

For example if $X,Y$ are affine, then $\text{Qcoh}(X \times_R Y)$ is the $2$-coproduct of $\text{Qcoh}(X)$ and $\text{Qcoh}(Y)$. I think I can prove it also when $X,Y$ are projective over $R$.

Martin Brandenburg
  • 63.1k
  • 13
  • 207
  • 424