The inequalities of Chern classes and Riemann-Roch type inequalities

Abstract

Motivated by Kollár-Matsusaka's Riemann-Roch type inequalities, applying effective very ampleness of adjoint bundles on Fujita conjecture and log-concavity given by Khovanskii-Teissier inequalities, we show that for any partition $\lambda$ of the positive integer $d$ there exists a universal bivariate polynomial $Q_{\lambda }(x,y)$ which has deg $Q\le d$ and whose coefficients depend only on $n$, such that for any projective manifold $X$ of dimension $n$ and any ample line bundle $L$ on $X$, \begin{equation*} \left|c_λ(X)\cdot L^{n -d}\right|\leq \frac{Q_λ(L^{n}, K_X \cdot L^{n -1} )}{(L^{n})^{d-1}}, \end{equation*} where $K_X$ is the canonical bundle of $X$ and $c_{\lambda }(X)$ is the monomial Chern class given by the partition $\lambda$. As a special case, when $K_X$ or $-K_X$ is ample, this implies that there exists a constant $c_n$ depending only on $n$ such that for any monomial Chern classes of top degree, the Chern number ratios \begin{equation*} \left|\frac{c_λ(X)}{c_1 (X) ^{n}}\right|\leq c_n, \end{equation*} which recovers a recent result of Du-Sun. The main result also yields an asymptotic version of the sharper Riemann-Roch type inequality. Furthermore, using similar method we also obtain inequalities for Chern classes of the logarithmic tangent bundle.

16 pages; V2 mainly adds a section on the inequalities for Chern classes of the logarithmic tangent bundle; V3, minor revisions, to appear in Advances in Mathematics

References in corpus (1)

• Miyaoka type inequality for terminal threefolds with nef anti-canonical divisors