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Feb 25, 2014 at 17:56 comment added Alex Degtyarev @Brenin Yes, constant $j$-invariant. No, this is not birational to product. If the fiber has nontrivial automorphism, the monodromy $\pi_1(\text{base})\to\operatorname{Aut}(\text{fiber})$ may be nontrivial. I don't see how this can be undone birationally.
Feb 25, 2014 at 15:09 comment added Brenin @AlexDegtyarev: Just to be sure: is "isotrivial" a synonym of "having isomorphic fibers", isn't it? This also means, for the family, to be birational to the product family (I guess).
Feb 23, 2014 at 21:22 comment added Alex Degtyarev The key word is isotrivial. They are easily constructed as quotients of $(\text{disk})\times(\text{elliptic curve})$.
Feb 23, 2014 at 21:21 comment added Damian Rössler The fibres of an elliptic surface are not isomorphic to each other in general.
Feb 23, 2014 at 17:50 history answered Alex Degtyarev CC BY-SA 3.0