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Aug 9, 2016 at 11:39 vote accept Daniel Loughran
Aug 8, 2016 at 22:05 answer added Sasha timeline score: 5
Aug 8, 2016 at 20:11 comment added Daniel Loughran But both these conic bundles arise from pencils! And by definition, a pencil gives rise to a morphism $S \to \mathbb{P}^1$.
Aug 8, 2016 at 20:10 comment added Daniel Loughran I have clarified my construction. If you have a quartic del Pezzo surface with a conic $Q$ then it in fact has 2 conics bundles. Namely you consider the pencil of hyperplanes which contain $Q$ and take the residual intersection. This gives one conic bundle. But then you can of course run this construction with the residual conics to get another conic bundle.
Aug 8, 2016 at 20:08 history edited Daniel Loughran CC BY-SA 3.0
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Aug 8, 2016 at 19:31 comment added Sasha I don't quite see why do you think a conic bundle constructed from a conic $Q$ satisfies $C(k) \ne 0$. In fact, $Q$ is not a fiber of this conic bundle. On a contrary, fibers are conics residual to Q.
Aug 8, 2016 at 17:05 history asked Daniel Loughran CC BY-SA 3.0