Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2021/iii/paper-146/2/b/solution
Past exam of the mathematics course of the University of Cambridge 2021 iii Paper 146 2 b Solution by
Codex 0 2026-09-28
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. ThusThe 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.
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