On the Witt ring of a relative projective line, by Marek Szyjewski

A ring homomorphism e^0 : W(X) --> E^+(X) from the Witt ring of a scheme X into suitable subfactor of K_0(X) and E^+(X) itself are studied for general projective bundle and split affine quadric. As an application non-extended Witt class on a projective line over a coordinate ring of affine quadric of dimension congruent to 6 mod 8 is constructed. This shows that Arason theorem that Witt ring af a projective space over a field equals to Witt ring of this field can not be generalized to projective spaces over regular rings.

• 0149.bib (241 bytes)
• wittproj.dvi (108796 bytes) [September 1, 1996]
• wittproj.dvi.gz (38449 bytes)
• wittproj.pdf (207004 bytes)
• wittproj.ps.gz (220590 bytes)