O(D) for D a divisor

Last modified date: <%+ tp.file.last_modified_date() %>


- Tags: - #todo/untagged - Refs: - #todo/add-references - Links: - Serre’s theorem - divisor


O(D) for D a divisor

Idea: for \(X = \mathop{\mathrm{Proj}}S, S\in {\mathsf{gr}\,}_{\mathbf{Z}}\mathsf{CRing}\). define \({\mathcal{O}}_{\mathop{\mathrm{Proj}}S}(d) = \text{Ét}{\Sigma^d S}\) where for \(A\in \mathsf{CRing}\) and $M\in {}_{A}{\mathsf{Mod}} $, \(\text{Ét}M\) is the sheaf of continuous sections of the etale space \begin{align*}\coprod_{p\in \operatorname{Spec}A} M \left[ { \scriptstyle { {p}^{-1}} } \right] \to \operatorname{Spec}A.\end{align*} attachments/Pasted%20image%2020220418124236.png

attachments/Pasted%20image%2020220418100445.png

  • Idea: \({\mathcal{O}}_{{\mathbf{P}}^n_{/ {k}} }(d)\) are homogeneous polynomials of degree \(d\).
  • For \(M = \oplus_k M_k\) a graded module and \(H^0(X; {\mathcal{F}}) = M_0\), twisting yields \(H^0(X; {\mathcal{F}}\otimes{\mathcal{O}}(d)) = M_d\). homogeneous degree \(d\) elements.
  • For \({\mathcal{J}}\) the ideal sheaf of $Y \subseteq {\mathbf{P}}^n_{/ {k}} $, \(H^0(Y; {\mathcal{J}}\otimes{\mathcal{O}}(d))\) are homogeneous polynomials of degree \(d\) that vanish on \(Y\).
  • Def: \({\mathcal{O}}(1) \coloneqq?\)
  • Def: \({\mathcal{O}}(n) \coloneqq{\mathcal{O}}(1)^{\otimes n}\)?
#todo/untagged #todo/add-references