The Miyaoka–Yau inequality and equality criterion for arbitrary weights

Assume Setup, with XX a Fano manifold and ωc1(X)\omega \in c_1(X). Let v ⁣:PR>0v \colon P \to \mathbb{R}_{>0} be a weight, let V\mathscr{V} be a canonical extension sheaf with extension class λc1(X)\lambda c_1(X) for some λ>0\lambda>0, and let δv(X)\delta'_v(X) denote the greatest Ricci lower bound associated with vv. For a saturated subsheaf FV\mathcal{F}\subset\mathscr{V} of rank rr, write c1T(F)c_1^{\mathbb{T}}(\mathcal{F}) for its equivariant first Chern class. Miyaoka–Yau conjecture for arbitrary weights. There exists such a canonical extension sheaf V\mathscr{V} for which

(c1T(F)v(c1T(X)))(1δv(X)(1rn+1))(c1T(X)v(c1T(X)))(c_1^{\mathbb{T}}(\mathcal{F})\cdot v(c_1^{\mathbb{T}}(X)))\le\left(1-\delta'_v(X)\left(1-\frac{r}{n+1}\right)\right)(c_1^{\mathbb{T}}(X)\cdot v(c_1^{\mathbb{T}}(X)))

for every saturated subsheaf FV\mathcal{F}\subset\mathscr{V} of rank rr. This is proposed as an equivariant Miyaoka–Yau inequality with an equality criterion analogous to the known result for the relevant special weight; the arbitrary-weight case remains open.

Sources & referencesView supporting material

Primary source

Tomoyuki Hisamoto and Masataka Iwai, “The Miyaoka-Yau inequality and the delta invariant for Fano varieties”, arXiv:2607.25181 (2026).

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