Exceptional-sheaf version of the Bogomolov–Gieseker inequality

Let XX be the canonical line bundle of P3\mathbb{P}^3, with projection π:XP3\pi:X\to\mathbb{P}^3. Let βR\beta\in\mathbb{R} and let E\mathcal{E} be an exceptional locally free sheaf of finite rank on P3\mathbb{P}^3. Let μ1(E)\mu_1(\mathcal{E}), μ2(E)\mu_2(\mathcal{E}), αEβ\alpha_{\mathcal{E}}^{\beta}, viβv_i^{\beta}, and the hearts and tilt slope appearing below be as defined in the source. Exceptional-sheaf Bogomolov–Gieseker conjecture. (1) If β<μ1(E)\beta<\mu_1(\mathcal{E}) and iECoh0β(X)i_*\mathcal{E}\in\mathrm{Coh}_{0}^{\beta}(X) is νβ,αEβ\nu^{\beta,\alpha_{\mathcal{E}}^{\beta}}-stable, then there exists a0<v3β(iE)v1β(iE)a_0<\frac{v_3^{\beta}(i_*\mathcal{E})}{v_1^{\beta}(i_*\mathcal{E})} such that every νβ,αEβ\nu^{\beta,\alpha_{\mathcal{E}}^{\beta}}-semistable object ECoh0β(X)E\in\mathrm{Coh}_{0}^{\beta}(X) with tilt-slope β\beta and HomCoh0β(X)(iE,E)=0\mathrm{Hom}_{\mathrm{Coh}_{0}^{\beta}(X)}(i_*\mathcal{E},E)=0 satisfies

v3β(E)a0v1β(E).v_3^{\beta}(E)\leqslant a_0v_1^{\beta}(E).

(2) If β>μ2(E)\beta>\mu_2(\mathcal{E}) and iE[1]Coh0β(X)i_*\mathcal{E}[1]\in\mathrm{Coh}_{0}^{\beta}(X) is νβ,αEβ\nu^{\beta,\alpha_{\mathcal{E}}^{\beta}}-stable, then there exists a0<v3β(iE)v1β(iE)a_0<\frac{v_3^{\beta}(i_*\mathcal{E})}{v_1^{\beta}(i_*\mathcal{E})} such that every such EE with HomCoh0β(X)(iE[1],E)=0\mathrm{Hom}_{\mathrm{Coh}_{0}^{\beta}(X)}(i_*\mathcal{E}[1],E)=0 satisfies the same inequality. This is proposed as an analogue of the main Bogomolov–Gieseker conjecture after removing the exceptional object from consideration; no resolution is given.

Sources & referencesView supporting material

Primary source

Tianle Mao, “Stability conditions on the canonical line bundle of P^3”, arXiv:2501.15251 (2025).

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