Syzygy conjecture for general projections of canonical curves

Let CPg1C\hookrightarrow\mathbb{P}^{g-1} be a generic canonical curve of genus g9g\geq 9, and let pPg1p\in\mathbb{P}^{g-1} be a generic point. Write CC' for the projection of CC away from pp to a hyperplane, and let b~t,1\widetilde{b}_{t,1} denote the graded Betti numbers of its syzygy resolution. Then the canonical projection conjecture. The curve CC' has the following properties: (1) it satisfies N~Cliff(C)3\widetilde{N}_{\operatorname{Cliff}(C)-3}; (2) the length of the linear strands of its syzygy resolution is gCliff(C)3g-\operatorname{Cliff}(C)-3, meaning that b~t,1=0\widetilde{b}_{t,1}=0 if and only if 1tgCliff(C)31\leq t\leq g-\operatorname{Cliff}(C)-3; and (3) if g=2kg=2k, then b~k2,1=b~k3,2=1\widetilde{b}_{k-2,1}=\widetilde{b}_{k-3,2}=1, with the extra syzygy having maximal rank. These predictions refine the expected syzygies of general projections and remain conjectural in the stated generality.

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Primary source

Li Li, “Syzygies of general projections of canonical and paracanonical curves”, arXiv:2407.08492 (2024).

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