Timeline for Is canonical class a topological invariant?
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| Mar 14, 2012 at 5:45 | vote | accept | Yuchen Liu | ||
| Jul 16, 2011 at 16:39 | comment | added | Tim Perutz | (Artie's question, and my response to it, are now covered by the edit to my answer.) | |
| Jul 16, 2011 at 1:20 | history | edited | Tim Perutz | CC BY-SA 3.0 |
Elementary and not-so elementary counterexamples. Links.; deleted 7 characters in body
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| Jul 15, 2011 at 20:05 | comment | added | Tim Perutz | Artie, yes: Wall says that if $N$ is a simply connected, closed oriented 4-manifold which is either indefinite, or has $b_2(N)<9$, and $M= N \# (S^2×S^2)$, then all automorphisms of the intersection form of $M$ are realised by diffeos. If I take $N= \mathbb{C}P^2$ then $M$ is the 2-fold blow up of $\mathbb{C}P^2$. | |
| Jul 15, 2011 at 19:30 | comment | added | user5117 | "bz" -> "by" (ah, the joys of switching between German and English keyboard layout twice a day...) | |
| Jul 15, 2011 at 19:28 | comment | added | user5117 | Dear Tim, may I ask you to elaborate a little on (1)? More precisely, are you saying that Wall's theorem allows one to realise any automorphism of the lattice bz a diffeomorphism? (I don't have access to MathSciNet where I am, so I can't check this for myself.) I guess not, but that seems to be one interpretation. | |
| Jul 15, 2011 at 15:44 | history | answered | Tim Perutz | CC BY-SA 3.0 |