Skip to main content
8 events
when toggle format what by license comment
S Oct 30 at 7:15 history suggested Viktor Vaughn CC BY-SA 4.0
Fix LaTeX expressions
Oct 30 at 3:58 review Suggested edits
S Oct 30 at 7:15
Apr 13, 2017 at 12:58 history edited CommunityBot
replaced http://mathoverflow.net/ with https://mathoverflow.net/
Nov 20, 2010 at 19:10 comment added William Stein Additional remark: I just carefully reread Section 1 of Serre-Tate (Good Reduction of Abelian Varieties), and that makes everything crystal clear.
Nov 20, 2010 at 18:17 comment added William Stein Brian -- thanks for clarifying Pete's argument, which is definitely backwards.
Aug 19, 2010 at 16:41 comment added BCnrd Pete, your suggested argument sounds a bit puzzling, insofar as you're not mentioning the most crucial part, which is the role of finite etale torsion levels which are fiberwise "schematically dense" and provide a bridge between the two fibers. That is, in your 3rd line it seems like you should have said "special fiber", not "generic fiber", and then you need to haul out the finite etale torsion levels to promote that to vanishing on the generic fiber, etc. (The example of $[p]$ on an elliptic curve with additive reduction shows the necessity of using finite etale torsion.)
Aug 19, 2010 at 3:05 comment added Pete L. Clark WS: Yes, the reduction map always induces an injection on the endomorphism ring. This can be seen, for instance, by thinking about the Neron models: if the map were not injective, there would be a nonzero endomorphism which agrees on the generic fiber with the zero endomorphism, contradicting density of the generic fiber.
Aug 19, 2010 at 1:00 history answered William Stein CC BY-SA 2.5