Take the Hirzebruch surface with its standard toric Kähler structure. Let be its negative section of a Hirzebruch surface, and let represent the fiber class of a Hirzebruch surface and meet once. Thus
The preceding smoothing produces an embedded symplectic in class .
Suppose a compatible almost complex structure made all three surfaces almost complex. Since and are distinct, Positive intersection of J-holomorphic curves would imply . Homologically, however,
a contradiction. Hence this example cannot admit such a simultaneous compatible structure.
On , let be the negative section of a Hirzebruch surface, so , and let be the fiber class of a Hirzebruch surface, with and . The line bundle is very ample. Indeed, the toric ampleness criterion for is
and on a smooth complete toric variety every ample line bundle is very ample. These inequalities hold for .
Explicitly, after choosing the standard lattice coordinates for , its lattice polytope of a toric divisor is
The monomials indexed by the lattice points of this polygon separate torus orbits and tangent directions, so their Kodaira map is a closed embedding. This directly verifies that the resolved proper toric surface is projective.
Picard lattice of a Hirzebruch surface Created 2026-09-28 Updated 2026-10-05
For the Hirzebruch surface , the negative section of a Hirzebruch surface and a fiber class of a Hirzebruch surface freely generate and satisfy