Example 6.13 . [04KJ]
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Example 6.13.
Consider a smooth proper Lagrangian fibration , with and , where is the moment map of a free action and is invariant. Assuming is contractible and having chosen bases of as in and above, on we can apply the admissible change of coordinates as in Proposition 6.5. Clearly is (tautologically) a fake stitched fibration. Given a Lagrangian section of , it easy to see that the normal form for is of the type where and
i.e. the projection composed with a linear change of coordinates. In this case the only non-zero invariant is which is given by
Clearly is fibrewise constant.