Friday, 27 April 2012

ag.algebraic geometry - Divisors on Proj(UFD)

Well, if you read on to Chapter 2, exercise 6.3, then it is stated that:
Cl(A)congCl(X)/mathbbZ[H]


here [H] represents the hyperplane section. So the answer is yes.



There is a less well-known but very nice generalization. Suppose that X is smooth. Let R=Am be the local ring of A at the irrelevant ideal. Then one has a (graded) isomorphism of mathbbQ- vector spaces:



CH(X)mathbbQ/[H]CH(X)mathbbQcongA(R)mathbbQ



Here CH(X) is the Chow ring of X and A(R) is the total Chow group of R. Details can be found in this paper by Kurano.

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