An invariant of quadratic forms over schemes, by Marek Szyjewski

A ring homomorphism e^0: W(X)--> EX from the Witt ring of a scheme X into proper subquotient EX of the Grothendieck ring K_0(X) is a natural generalisation of dimension index for Witt ring of a field. In the case of even dimensional projective quadric X over a field F the value of e^0 on the Witt class of bundle of endomorphisms E of an indecomposable component V_0 of the Swan sheaf U with trace of product as a bilinear form \theta is outside of the image of composition W(F)--> W(X)--> E(X). Therefore the Witt class of (E,\theta) is not extended from F.

This paper has appeared as paper 19 in Documenta Mathematica, volume 1.


Marek Szyjewski <szyjewski@gate.math.us.edu.pl>
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