Timeline for Request: intermediate-level proof: every 2-homology class of a 4-manifold is generated by a surface.
Current License: CC BY-SA 2.5
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 28, 2010 at 6:52 | comment | added | Dylan Thurston | Note that these "actual geometry" arguments get stuck at some point, before the result is false. Specifically, $H_6$ is always represented by surfaces, but local techniques like I sketch above get stuck already for $H_4$ (independent of the ambient space), since not every 4-manifold is the boundary of a 5-manifold. | |
| Apr 28, 2010 at 5:34 | comment | added | Herb | Thank you both. Dylan's answer is nice , in that one can see the actual geometry. Torsten's answer is a bit out-of-my-league at this point, but I will still try to understand it. | |
| Apr 28, 2010 at 5:32 | vote | accept | Herb | ||
| Apr 25, 2010 at 18:21 | comment | added | Torsten Ekedahl | I love these kinds of arguments! | |
| Apr 25, 2010 at 15:08 | history | answered | Dylan Thurston | CC BY-SA 2.5 |