Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

If I have two schemes $X$ and $Y$, which are such that my question makes sense (I guess, they should be abelian varieties over a field $k$, so assume this).

Then I have often read, but nowhere found a proper definition, the notion of a $\mathbb{G}_{m}$- biextension of $X \times Y$.

I would be very glad if someone could explain this notion properly to me, maybe with an example (I think one often speaks of the "Poincaré-Biextension).

share|improve this question

1 Answer 1

The definition is not often written down as it is rather messy. A precise definition of a biextension can be found in SGA7.1, exposees VII and VIII. The Poincare Biextension is discussed in the article of Moret-Bailly in Asterisque 127 (though this reference is in no way canonical).

I am sorry that this answer is very minimal, but given how long the question has been sitting here I thought something was better than nothing!

David Holmes

share|improve this answer
    
Welcome, David! Why don't you register on this site properly? It would be good to have you around. –  Alex B. Jan 7 '13 at 11:41

Your Answer

 
discard

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.