Bloch's formula

In algebraic K-theory, a branch of mathematics, Bloch's formula, introduced by Spencer Bloch for $K_2$, states that the Chow group of a smooth variety X over a field is isomorphic to the cohomology of X with coefficients in the K-theory of the structure sheaf $\mathcal{O}_X$; that is,

$\operatorname{CH}^q(X) = \operatorname{H}^q(X, K_q(\mathcal{O}_X))$

where the right-hand side is the sheaf cohomology; $K_q(\mathcal{O}_X)$ is the sheaf associated to the presheaf $U \mapsto K_q(U)$, U Zariski open subsets of X. The general case is due to Quillen.^[1] For q = 1, one recovers $\operatorname{Pic}(X) = H^1(X, \mathcal{O}_X^*)$. (see also Picard group.)

The formula for the mixed characteristic is still open.

References

1. For a sketch of the proof, besides the original paper, see http://www-bcf.usc.edu/~ericmf/lectures/zurich/zlec5.pdf

• Daniel Quillen: Higher algebraic K-theory: I. In: H. Bass (ed.): Higher K-Theories. Lecture Notes in Mathematics, vol. 341. Springer-Verlag, Berlin 1973. ISBN 3-540-06434-6