Abstract
Much of the intersection theory developed in this text is valid for more general schemes than algebraic schemes over a field. A convenient category, sufficient for applications envisaged at present, is the category of schemes X of finite type over a regular base scheme S. Using an appropriate definition of relative dimension, one has a notion of k-cycle on X, and a graded group A * (X) of rational equivalence classes, satisfying the main functorial properties of Chaps. 1-6. The Riemann-Roch theorem also holds; in particular
The main missing ingredient in such generality is an exterior product If S is one-dimensional, however, there is such a product. In particular,
if X is smooth over S, then A * (X) has a natural ring structure.
When S = Spec (R),R a discrete valuation ring, and X is a scheme over S, with general fibre X° and special fibre, there are specialization maps
which are compatible with all our intersection operations. If X is smooth over S, σ is a homomorphism of rings.
For proper intersections on a regular scheme, Serre has defined intersection numbers using Tor. For smooth schemes over a field, these numbers agree with those in § 8.2. Indeed, even for improper intersections, a Riemann-Roch construction shows how to recover intersection classes from Tor, at least with rational coefficients.
Although higher K-theory is outside the scope of this work, the chapter concludes with a brief discussion of Bloch’s formula
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© 1998 Springer Science+Business Media New York
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Fulton, W. (1998). Generalizations. In: Intersection Theory. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-1700-8_21
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DOI: https://doi.org/10.1007/978-1-4612-1700-8_21
Publisher Name: Springer, New York, NY
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