Miyaoka-type Chern class inequalities for generically nef sheaves

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Let XX be a compact Kähler manifold, let E\mathcal{E} be a torsion-free coherent sheaf of rank rr, and let α1,…,αn−2\alpha_1,\ldots,\alpha_{n-2} be Kähler classes on XX. A sheaf is generically nef with respect to these classes when its restriction to a sufficiently general complete-intersection curve has nef quotient behavior in the sense used in the source. Miyaoka's conjecture. (1) If c1(E)c_1(\mathcal{E}) is nef and E\mathcal{E} is generically nef, then

c2(E)α1⋯αn−2≥0.c_2(\mathcal{E})\alpha_1\cdots\alpha_{n-2}\geq 0.

(2) If β\beta is a nef class and E\mathcal{E} is α1⋯αn−2β\alpha_1\cdots\alpha_{n-2}\beta-semistable, then

(c2(E)−r−12rc1(E)2)α1⋯αn−2≥0.\left(c_2(\mathcal{E})-\frac{r-1}{2r}c_1(\mathcal{E})^2\right)\alpha_1\cdots\alpha_{n-2}\geq 0.

Part (2) implies part (1) by the argument cited in the source. The conjecture is solved when XX is projective and all the classes involved lie in the Néron–Severi group, but remains open in the general compact Kähler setting.

References

Primary source

Masataka Iwai and Shin-ichi Matsumura, “Abundance theorem for minimal compact Kähler manifolds with vanishing second Chern class”, arXiv:2205.10613 (2022).

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