Manin obstruction

From Encyclopedia of Mathematics
(Redirected from Brauer–Manin obstruction)
Jump to: navigation, search

Brauer–Manin obstruction

An invariant attached to a geometric object $X$ which measures the failure of the Hasse principle for $X$: that is, if the obstruction is non-trivial, then $X$ may have points over all local fields but not over a global field.

For abelian varieties the Manin obstruction is just the Tate-Shafarevich group and fully accounts for the failure of the local-to-global principle. There are however examples, due to Skorobogatov, of varieties with trivial Manin obstruction which have points everywhere locally and yet no global points.


How to Cite This Entry:
Brauer–Manin obstruction. Encyclopedia of Mathematics. URL: