Phantom-category existence and deformation conjecture for critical blowups of Hirzebruch surfaces
Let be a nonnegative integer, set , and let be obtained by blowing up at general points. Let be a subcategory of , and let denote the first cohomology of the tangent sheaf while denotes the second Hochschild cohomology of . Phantom-category existence and deformation conjecture. The category has a phantom subcategory orthogonal to an exceptional collection of line bundles of maximal length. Furthermore, the map
is an isomorphism, so that for . This conjecture predicts distinct phantom categories at the critical number of blowups, distinguished by their Hochschild cohomology and deformation behavior; no resolution is given in the source.
References
Primary source
Kimoi Kemboi, Daniel Krashen, Tianle Liu, Yeqin Liu, Eoin Mackall, Svetlana Makarova, Alexander Perry, Antonios-Alexandros Robotis and Sridhar Venkatesh, “A Looming of phantoms”, arXiv:2511.05381 (2025).
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