ScalingStacks

Example 6.21 . [04KU]

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Example 6.21.

A simple example of stitched Lagrangian fibration which can be constructed using Theorem 6.19 is as follows. Define the sequence ℓc\ell^{c} to be identically zero and choose the terms of ℓd\ell^{d} and ℓe\ell^{e} to be zero except the first order ones, which we define to be

ℓ1d=m1​d​y2andℓ1e=m2​d​y3.\ell_{1}^{d}=m_{1}\,dy_{2}\ \ \text{and}\ \ \ell_{1}^{e}=m_{2}\,dy_{3}.

Clearly ℓ1c\ell_{1}^{c}, ℓ1d\ell_{1}^{d} and ℓ1e\ell_{1}^{e} satisfy the integral conditions of Theorem 6.19, moreover they are fibrewise constant, therefore they define fake stitched fibrations. Since the fibration is smooth after a change of coordinates on the base, it induces an affine structure on the base. One can easily see that in the case m1=−1m_{1}=-1 and m2=1m_{2}=1 and U=ℝ3−ΔU=\mathbb{R}^{3}-\Delta, this affine structure is simple and affine isomorphic to a negative vertex of Example 3.12. Notice that we could also replace Δ\Delta with Δτ\Delta_{\tau} and obtain an affine structure which is isomorphic to the one in Example 3.13.

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