2. Statement of the results [04S9]
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2. Statement of the results
Let be a smooth hypersurface of degree . We choose homogeneous coordinates so that is transverse to coordinate hyperplanes and all their intersections. The complement of the coordinate hyperplanes in is . Denote . Then the hypersurface is given by equation , where
stands for affine coordinates in and is a polynomial with the Newton polyhedron from Example 5. Recall that we denote the real -dimensional torus with .
Theorem 1.
For every maximal dual -complex there exists a stratified -fibration . This fibration satisfies to the following properties
- •
the induced map is injective, where , is the geometric genus of ;
- •
for each primitive piece of (see Definition 5) the inverse image is an open pair-of-pants .
- •
for each -cell of there exists a point such that the fiber is a Lagrangian -torus ;
- •
there exist Lagrangian embedding , such that the cycles form a basis of .
Maximal dual -complexes exist for every degree and every dimension .
This theorem admits a straightforward generalization to toric varieties other than . Let be a bounded convex lattice polyhedron such that all singularities of the toric variety are isolated. Note that the isolated singular points of necessarily correspond to some vertices of . Consider the space of all polynomials of the type such that . Then for a generic choice of a polynomial from this space the closure in of the zero set of is a smooth hypersurface transverse to all toric subvarieties corresponding to the faces . All such are diffeomorphic and, if we equip them with the symplectic form from , are symplectomorphic varieties.
Theorem 1’.
For every maximal dual -complex there exists a stratified -fibration . This fibration satisfies to the following properties
- •
the induced map is injective, where , is the geometric genus of ;
- •
for each primitive piece of (see Definition 5) the inverse image is an open pair-of-pants .
- •
for each -cell of there exists a point such that the fiber is a Lagrangian -torus ;
- •
there exist Lagrangian embeddings , such that the cycles form a basis of .
By Remark 1.9 not all convex lattice polyhedra have maximal dual complexes. However, in the case of (the polyhedra corresponding to the projective space), such subdivisions exists for any . Maximal subdivisions also exist for products of different (this corresponds to hypersurfaces in the product of projective spaces). It is conjectured that for any lattice polyhedron there exists a sufficiently large integer that (the result of scaling of by ) has a maximal subdivision.
The next theorem describes the behavior of the fibration with respect to a complex structure on . Recall that, unlike the smooth and symplectic structures, the complex structure on depends on the polynomial and not just on .
Recall that a map is called a totally real fibration if for any the tangent space to the fiber through is totally real i.e. contains no positive-dimensional complex subspaces (as long as the fiber is smooth near ). We say that a hypersurface is defined over if it can be obtained as the closure of the zero set of a polynomial whose coefficients are real.
Theorem 2.
For every maximal dual -complex there exists a smooth hypersurface defined over such that the map from Theorem 1’ preserves the real structure of , i.e. . Furthermore, is a totally real fibration.
Theorems 1’ and 2 can be extended further to polyhedra corresponding to toric varieties with non-isolated singularities. However, in order to do that, one has to modify the definition of stratified fibrations to include singular total spaces . We do not do that. In the next theorem we no longer have any restrictions on the convex lattice polyhedron , but its statement concerns only the toric, non-singular, part of the hypersurface .
Theorem 3.
For every maximal dual -complex there exists a stratified -fibration . This fibration satisfies to the following properties
- •
the induced map is injective, where , is the geometric genus of ;
- •
for each primitive piece of (see Definition 5) the inverse image is an open pair-of-pants .
- •
for each -cell of there exists a point such that the fiber is a Lagrangian -torus ;
- •
there exist Lagrangian embeddings , such that the cycles form a basis of .
Remark 2.1.
These theorems generalize to complete intersections. The base of the fibration in this case is the intersection of the maximal dual balanced polyhedra for the corresponding hypersurfaces (we have to choose them in a mutually general position).
From a different point of view the base is dual to a maximal mixed lattice subdivision of the Newton polyhedra of the participating equations. The primitive pieces for complete intersections are products of the primitive pieces for hypersurfaces. Sturmfels’ generalization [14] of the patchworking technique allows to produce in this case the Lagrangian lifts of the base cycles.
This generalization will be the subject of a future paper.