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Mar 23, 2015 at 15:10 history edited Roberto Pignatelli CC BY-SA 3.0
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Mar 23, 2015 at 14:50 comment added Roberto Pignatelli The assumption $p_g=0$ gives $h^2(X,{\mathbb C})=h^{1,1}$ and therefore $H^2(X,{\mathbb Q}) \subset H^{1,1}$: these surfaces have automatically maximal Picard number.
Mar 23, 2015 at 14:19 comment added abx These surfaces are projective, hence $H^2(S,\Bbb{Q})$ is spanned by the class of an ample divisor. And, yes, a curve of negative square on a smooth surface can always be contracted.
Mar 23, 2015 at 13:04 comment added Marco Golla Is it automatic that for all these surfaces there is a holomorphic curve representing some nontrivial homology class? Also, why can you always contract negative curves? (This could well be a standard argument I am not aware of...)
Mar 23, 2015 at 9:25 history answered Roberto Pignatelli CC BY-SA 3.0