MathOverflow is a question and answer site for professional mathematicians. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Hello everyone,

A quick question, as I'm not sure I got it right.

Let $X=\mathbb{P}^1 \times \mathbb{P}^1$ and let $\mathcal{O}(a,b):=\pi^*_1\mathcal{O}(a)\otimes \pi^*_2\mathcal{O}(b)$. Is there a general expression for $$RHom_X(\mathcal{O}(a,b),\mathcal{O}(x,y))$$

Thank you

Edit: Whoops, I actually meant derived Hom, but I think I got it now

share|cite|improve this question
Are you looking for something different than $H^0(X, \mathcal{O}(x-a, y-b))$? – Mike Skirvin Jun 30 '10 at 17:52

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.