Inequalities of Chern classes on nonsingular projective $n$-folds of Fano and general type with ample canonical bundle

Abstract

Let $X$ be a nonsingular projective $n$-fold $(n\ge 2)$ of Fano or of general type with ample canonical bundle $K_X$ over an algebraic closed field $\kappa$ of any characteristic. We produce a new method to give a bunch of inequalities in terms of all the Chern classes $c_1,c_2,\cdots ,c_n$ by pulling back Schubert classes in the Chow group of Grassmannian under the Gauss map. Moreover, we show that if the characteristic of $\kappa$ is $0$, then the Chern ratios $(\frac{c_{2,1^{n-2}}}{c_{1^n}},\frac{c_{2,2,1^{n-4}}}{c_{1^n}},\cdots ,\frac{c_n}{c_{1^n}})$ are contained in a convex polyhedron for all $X$. So we give an affirmative answer to a generalized open question, that whether the region described by the Chern ratios is bounded, posted by Hunt (\cite{Hun}) to all dimensions. As a corollary, we can get that there exist constants $d_1$, $d_2$, $d_3$ and $d_4$ depending only on $n$ such that $d_1{K}_X^n\le {\chi }_{top}(X)\le d_2{K}_X^n$ and $d_3{K}_X^n\le \chi (X,{\mathcal{O}}_X)\le d_4{K}_X^n$. If the characteristic of $\kappa$ is positive, $K_X$ (or $-K_X$) is ample and ${\mathcal{O}}_X(K_X)$ (${\mathcal{O}}_X(-K_X)$, respectively) is globally generated, then the same results hold.

Cited by in corpus (1)

• Chern class inequalities on polarized manifolds and nef vector bundles