5.6. Proof of Theorems 2 and 4 [04TF]
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5.6. Proof of Theorems 2 and 4
Here we prove that is non-singular and that satisfies to all hypotheses of Theorem 3 for a large .
Note that , where stands for the scalar product, at any such that . Let be an open -cell.
Lemma 5.5.
There exists monomials that dominate in a neighborhood of . Namely, any other monomial evaluated at a point near has a smaller order by . Furthermore, the hypersurface
is isomorphic to the hyperplane under the multiplicative change of coordinates by an element of .
Proof.
This follows from the maximality of . By Proposition 1.1 is dual to a -dimensional polyhedron from a subdivision of . Since is maximal, this polyhedron is the standard -simplex up to action of . ∎
This lemma implies that is non-singular for large . Indeed, it is covered by a finite number of open sets and in each set it is a small perturbation of a hyperplane. Furthermore, its compactification is smooth and transverse to the coordinate hyperplanes as the same reasoning with the terms of smaller order applies to the affine charts of .
Our next step is to isotop over as in 3.4. Recall that was defined in 5.5 as a small neighborhood of in . Denote
By the last conclusion of Proposition 3.6 these manifolds coincide over for . We set
Note that for is isotopic to by the same isotopy as in the proof of Proposition 3.6 since all other monomials of have smaller order in . This proves Theorem 4. As in Proposition 3.6 the closure is a smooth manifold. Similarly, is isotopic to in .
In the proof of Theorem 3 we may assume that since its closure is smooth and transverse to the coordinate hyperplanes. Similarly, in the proof of Theorems 1, 1’ and 2 we may assume that . We define as a composition of the isotopy (note that since this map is realized by an ambient isotopy it is a symplectomorphism by Moser’s trick), the map and the projection . To define we compactify the previous construction by using and the reparametrized moment map to as in 1.3.

This proves Theorem 2, since everything in our construction is equivariant with respect to complex conjugation as long as in the patchworking polynomial are real. The fibration is totally real since it is totally real for a hyperplane.