Descent on fibrations over the projective line
Descent on fibrations over the projective line
复制标题
投影线上的纤维下降
DOI:
--
复制
发表时间:
1996
期刊:
影响因子:
--
通讯作者:
A. Skorobogatov
中科院分区:
文献类型:
--
作者:
A. Skorobogatov
We formulate a general set-up for the descent method of J.-L. Colliot-Thelene and J. J. Sansuc applied to varieties fibred over the projective line over a number field. This makes it possible to prove that the Manin obstruction to the Hasse principle and weak approximation is the only one provided there are only few "degenerate" fibres (usually two, three in some cases), and that "sufficiently many" smooth fc-fibres satisfy the Hasse principle and weak approximation. We introduce a new concept of what should be called a "degenerate" fibre, the so called "split" fibres, the property which depends only on the generic fibre and not on the choice of a particular model. This yields a simpler and more general approach to the previous results of that kind. 0. Introduction. Motivated by Hasse's theorem on quadratic forms one says that the Hasse principle holds for a family of (geometrically integral, smooth and proper) varieties over a number field k9 if for every member of this family the existence of rational points over all the completions of k implies the existence of a ^-rational point. The fact that the Hasse principle holds for some family signif icantly simplifies the study of its arithmetic, because the problem of determining whether or not there is a ^-rational point is then reduced to a finite number of