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Mar 28, 2013 at 11:35 history edited Liviu Nicolaescu CC BY-SA 3.0
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Mar 28, 2013 at 9:29 history edited Liviu Nicolaescu CC BY-SA 3.0
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Mar 27, 2013 at 23:32 comment added Eric Wofsey Complex line bundles are classified by $H^2$ (with coefficients in $\mathbb{Z}$), so you can get extra line bundles on a product that come from $H^1(X)\otimes H^1(Y)$. The simplest example of this is for $X=Y=S^1$: every complex line bundle on $X$ or $Y$ is trivial, but $H^2(X\times Y)=\mathbb{Z}$.
Mar 27, 2013 at 22:20 comment added Hugo Chapdelaine Ok, I was being idiot
Mar 27, 2013 at 21:38 vote accept Hugo Chapdelaine
Mar 27, 2013 at 21:38 comment added Hugo Chapdelaine I see, so this explains why I was not able to construct such an example. What about complex line bundle?
Mar 27, 2013 at 20:25 history answered Liviu Nicolaescu CC BY-SA 3.0