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Oct 22, 2017 at 16:55 history edited Tsemo Aristide CC BY-SA 3.0
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Oct 22, 2017 at 14:27 comment added Marco Golla I can't find the reference you are giving in McDuff and Salamon. In any case, if you blow-up $\Sigma\times S^2$, then you still have plenty of 0-spheres, but the 4-manifold is not a fibre bundle (not even topologically). (Relative) minimality is a key assumption in McDuff's theorem.
Oct 22, 2017 at 13:58 history edited Tsemo Aristide CC BY-SA 3.0
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Oct 22, 2017 at 13:35 history edited Tsemo Aristide CC BY-SA 3.0
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Oct 22, 2017 at 13:02 history edited Tsemo Aristide CC BY-SA 3.0
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Oct 22, 2017 at 12:55 comment added Tsemo Aristide Minimality is not mentioned in the reference above.
Oct 22, 2017 at 12:24 history undeleted Tsemo Aristide
Oct 22, 2017 at 12:24 history edited Tsemo Aristide CC BY-SA 3.0
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Oct 22, 2017 at 12:20 history deleted Tsemo Aristide via Vote
Oct 22, 2017 at 12:11 comment added Marco Golla The existence of the diffeomorphism $e_i$ requires that $M$ be minimal (which is not assumed, here). Moreover, it's not true that $H_2$ of an irrational ruled surface has one generator; e.g. $H_2(\Sigma\times S^2) = \mathbb{Z}^2$, generated by a section and a fibre. (This is true for all bundles, actually.)
Oct 22, 2017 at 12:05 history answered Tsemo Aristide CC BY-SA 3.0