Greatest lower bounds on Ricci curvature for toric Fano manifolds

Greatest lower bounds on the transverse Ricci curvature of some toric Sasaki manifolds

We determine the greatest lower bounds on the transverse Ricci curvature of compact toric Sasaki manifolds with positive basic first Chern class and with the first Chern class of the contact bundle being trivial. This is based on Wang-Zhu's and Futaki-Ono-Wang's works, and is an analogue of C. Li's work on toric Fano manifolds.

The greatest Ricci lower bound, conical Einstein metrics and the Chern number inequality

We partially confirm a conjecture of Donaldson relating the greatest Ricci lower bound $R(X)$ to the existence of conical Kahler-Einstein metrics on a Fano manifold $X$. In particular, if $D\in |-K_X|$ is a smooth simple divisor and the Mabuchi $K$-energy is bounded below, then there exists a unique conical Kahler-Einstein metric satisfying $Ric(g) = βg + (1-β) [D]$ for any $β\in (0,1)$. We also construct unique smooth conical toric Kahler-Einstein metrics with $β=R(X)$ and a unique effective Q-divisor $D\in [-K_X]$ for all toric Fano manifolds. Finally we prove a Miyaoka-Yau type inequality f…

Mabuchi Solitons and Relative Ding Stability of Toric Fano Varieties

As a generalization of Kahler-Einstein metrics for Fano manifolds with nonvanishing Futaki invariant, Mabuchi solitons are critical points of a Calabi-type energy functional. We study their existence on toric Fano varieties and the underlying algebraic stability notion: relative Ding stability. As a toy model for a YTD type correspondence, a new feature is the emergence of a non-uniformly stable case. We show a partial coercivity for the modified Ding functionals in this case, and obtain singular Mabuchi solitons via a variational approach. In the unstable case, we determine the maximal destab…

On the limit behavior of metrics in continuity method to Kahler-Einstein problem in toric Fano case

This is a continuation of paper \cite{Li}. On any toric Fano manifold, we discuss the behavior of limit metric of a sequence of metrics, which are solutions to a continuity family of complex Monge-Ampere equations in Kahler-Einstein problem. We show that the limit metric satisfies a singular complex Monge-Ampere equation. This shows the conic type singularity for the limit metric. The information of conic type singularities can be read from the geometry of the moment polytope.

收缩Kähler-Ricci孤立子关于环面Fano纤维化

Shrinking Kähler-Ricci solitons on toric fano fibrations

本文证明了光滑环面Fano纤维化上存在完备的梯度收缩Kähler-Ricci孤立子，这是该领域的重要存在性结果。

环面Fano流形上广义Kähler--Ricci流的收敛性

Convergence of Generalized Kähler--Ricci Flow on Toric Fano Manifolds

本文在环面Fano流形上定义扩展Mabuchi泛函并证明其适定性，通过单调性证明广义Kähler-Ricci流收敛到Kähler-Ricci孤子，证实了Apostolov-Streets-Ustinovskiy猜想。

Kaehler-Ricci solitons on homogeneous toric bundles (II)

It is proved that an homogeneous toric bundles over a flag manifold G^\C/P admits a Kaehler-Ricci solitonic metric if and only if it is Fano. In particular, an homogeneous toric bundle of this kind is Kaehler-Einstein if and only if it is Fano and its Futaki invariant vanishes identically.

The α-Invariant on Toric Fano Manifolds

The global holomorphic α-invariant introduced by Tian is closely related with the study in the existence of Kahler-Einstein metric. We apply the result of Tian, Lu and Zelditch on polarized Kahler metrics to approximate plurisubharmonic functions and compute the α-invariant of toric Fano manifolds.

Generalized Futaki Invariant of Almost Fano Toric Varieties, Examples

The interpretation, due to T. Mabuchi, of the classical Futaki invariant of Fano toric manifolds is extended to the case of the Generalized Futaki invariant, introduced by W. Ding and G. Tian, of almost Fano toric varieties. As an application it is shown that the real part of the Generalized Futaki invariant is positive for all degenerations of the Fano manifold V_{38}, obtained by intersection of the Veronese embedding of ${\bf P}^3\times{\bf P}^2 \subset {\bf P}^{11}$ with codimension-two hyperplanes.

Relative $K$-stability and modified $K$-energy on toric manifolds

In this paper, we discuss the relative $K$-stability and the modified $K$-energy associated to the Calabi's extremal metric on toric manifolds. We give a sufficient condition in the sense of convex polytopes associated to toric manifolds for both the relative $K$-stability and the properness of modified $K$-energy. In particular, our results hold for toric Fano manifolds with vanishing Futaki-invariant. We also verify our results on the toric Fano surfaces.

The Calabi flow on toric Fano surface

We prove the longtime existence and convergence of the Calabi flow on toric Fano surfaces in a large family of Kahler classes where the class has positive extremal Hamiltonian potential and the initial Calabi energy is bounded by some constant. This is an extension of our previous work. We use the toric condition in a more essential way to rule out bubbles.

Multiplier ideal sheaves and the Kähler-Ricci flow on toric Fano manifolds with large symmetry

The purpose of this paper is to calculate the support of the multiplier ideal sheaves derived from the Kähler-Ricci flow on certain toric Fano manifolds with large symmetry. The early idea of this paper has already been in Appendix of \cite{futaki-sano0711}.

不允许存在极值 Kähler 度量的环面 Fano 流形

Toric Fano manifolds that do not admit extremal Kähler metrics

本文构造了维数为 10 的环面 Fano 流形，使其第一陈类中无极值 Kähler 度量，并通过乘积推广到所有 n≥11，回答了 Mabuchi 的问题。

Coupled Kähler-Ricci solitons on toric Fano manifolds

We prove a necessary and sufficient condition in terms of the barycenters of a collection of polytopes for existence of coupled Kähler-Einstein metrics on toric Fano manifolds. This confirms the toric case of a coupled version of the Yau-Tian-Donaldson conjecture. We also obtain a necessary and sufficient condition for existence of torus-invariant solutions to a system of soliton type equations on toric Fano manifolds. Some of these solutions provide natural candidates for the large time limits of a certain geometric flow generalizing the Kähler-Ricci flow.

Relative Ding and $K$-stability of toric Fano manifolds in low dimensions

The purpose of this paper is to clarify all of the uniformly relatively Ding stable toric Fano threefolds and fourfolds as well as unstable ones. The key player in our classification result is the Mabuchi constants, which can be calculated by combinatorial data of the associated moment polytopes due to the work of Yao [33]. In Tables 1-3, we give the list of uniform relative Ding stability of all toric Fano manifolds in dimension up to four with the values of the Mabuchi constants. As an application of our main theorem (Theorem 1.1), we clarify the difference between relative $K$-stability and…

Examples of non-symmetric Kähler-Einstein toric Fano manifolds

In this note we report on examples of 7- and 8-dimensional toric Fano manifolds that are not symmetric and still admit a Kaehler-Einstein metric. This answers a question first posed by V.V. Batyrev and E. Selivanova. The examples were found in the classification of toric Fano manifolds up to dimension 8 obtained by M. Oebro. We also discuss related open questions and conjectures.

Metric SYZ conjecture for certain toric Fano hypersurfaces

We prove the metric version of the SYZ conjecture for a class of Calabi-Yau hypersurfaces inside toric Fano manifolds, by solving a variational problem whose minimizer may be interpreted as a global solution of the real Monge-Ampère equation on certain polytopes. This does not rely on discrete symmetry.

Modified Futaki invariant and equivariant Riemann-Roch formula

In this paper, we give a new version of the modified Futaki invariant for a test configuration associated to the soliton action on a Fano manifold. Our version will naturally come from toric test configurations defined by Donaldson for toric manifolds. As an application, we show that the modified $K$-energy is proper for toric invariant Kähler potentials on a toric Fano manifold.

Generalized Kähler-Ricci flow on toric Fano varieties

We study the generalized Kähler-Ricci flow with initial data of symplectic type, and show that this condition is preserved. In the case of a Fano background with toric symmetry, we establish global existence of the normalized flow. We derive an extension of Perelman's entropy functional to this setting, which yields convergence of nonsingular solutions at infinity. Furthermore, we derive an extension of Mabuchi's $K$-energy to this setting, which yields weak convergence of the flow.

Kähler Ricci flow on Fano surfaces (I)

We show the properties of the blowup limits of \KRf solutions on Fano surfaces if Riemannian curvature is unbounded. As an application, on every toric Fano surface, we prove that \KRf converges to a Kähler Ricci soliton metric if the initial metric has toric symmetry. Therefore we give a new Ricci flow proof of existence of Kähler Ricci soliton metrics on toric surfaces.

Einstein-Kaehler Metrics on Symmetric Toric Fano Manifolds

Let $X$ be a complex toric Fano $n$-fold and ${\cal N}(T)$ the normalizer of a maximal torus $T$ in the group of biholomorphic authomorphisms $Aut(X)$. We call $X$ {\em symmetric} if the trivial character is a single ${\cal N}(T)$-invariant algebraic character of $T$. Using an invariant $α_G(X)$ introduced by Tian, we show that all symmetric toric Fano $n$-folds admit an Einstein-Kähler metric. We remark that so far one doesn't know any example of a toric Fano $n$-fold $X$ such that $Aut(X)$ is reductive, the Futaki character of $X$ vanishes, but $X$ is not symmetric.

Homogeneous toric bundles with positive first Chern class

A simple algebraic characterization of the Fano manifolds in the class of homogeneous toric bundles over a flag manifold $G^C/P$ is provided in terms of symplectic data.

The volume of Kähler-Einstein Fano varieties and convex bodies

We show that the complex projective space has maximal degree (volume) among all n-dimensional Kahler-Einstein Fano manifolds admitting a holomorphic C^*-action with a finite number of fixed points. The toric version of this result, translated to the realm of convex geometry, thus confirms Ehrhart's volume conjecture for a large class of rational polytopes, including duals of lattice polytopes. The case of spherical varieties/multiplicity free symplectic manifolds is also discussed. The proof uses Moser-Trudinger type inequalities for Stein domains and also leads to criticality results for mean…

通过Morse同伦的环面Fano曲面的同调镜像对称

Homological mirror symmetry of toric Fano surfaces via Morse homotopy

应用SYZ构造于环面Fano曲面，通过考虑矩多面体的Morse同伦而非Fukaya范畴来讨论同调镜像对称。

环面Fano簇的对称性概念

Symmetry notions for toric Fanos

本文综述环面簇跨多领域的对称性概念，明确其关联并补全文献缺失，同时给出此前难以理解的光滑环面簇自同构群Demazure 1970结构定理的简化证明。

Multiplier ideal sheaves and integral invariants on toric Fano manifolds

We extend Nadel's results on some conditions for the multiplier ideal sheaves to satisfy which are described in terms of an obstruction defined by the first author. Applying our extension we can determine the multiplier ideal sheaves on toric del Pezzo surfaces which do not admit Kähler-Einstein metrics. We also show that one can define multiplier ideal sheaves for Kähler-Ricci solitons and extend the result of Nadel using the holomorphic invariant defined by Tian and Zhu.

K-半稳定Fano簇高度的确界I，环面情形

Sharp bounds on the height of K-semistable Fano varieties I, the toric case

受Fujita结果启发，本文猜想整数射影空间在K-半稳定度量算术Fano簇中高度最大，并在n≤6时证明了环面Fano簇的该猜想，给出了Donaldson环面不变量与Odaka模高度的尖锐下界。

Tian 关于环面 Fano 的稳定化问题

Tian's stabilization problem for toric Fanos

本文解决了 Tian 于 1988 年提出的环面 Fano 流形的稳定化问题，利用凸几何函数表示复奇点指数，并解决了 2012 年关于多重反典范级数 Grassmannian 阈值的猜想。

Real Monge-Ampere equations and Kahler-Ricci solitons on toric log Fano varieties

We show, using a direct variational approach, that the second boundary value problem for the Monge-Ampère equation in R^n with exponential non-linearity and target a convex body P is solvable iff 0 is the barycenter of P. Combined with some toric geometry this confirms, in particular, the (generalized) Yau-Tian-Donaldson conjecture for toric log Fano varieties (X,D), saying that (X,D) admits a (singular) Kähler-Einstein metric iff it is K-stable in the algebro-geometric sense. We thus obtain a new proof and extend to the log Fano setting the seminal result of Zhou-Wang concerning the case when…

光滑环面Fano簇的切丛的斜率稳定性

Slope stability of tangent bundles of smooth toric Fano varieties

本文对三维至六维的8630个光滑环面Fano簇的切丛反典范斜率稳定性分类，引入根扭环面dP-纤维丛构造，明确稳定与凯勒-爱因斯坦性质的关系，完成相关分类与证明。

Gorenstein 环面 Fano 簇的渐近 Chow 半稳定性蕴含 Ding 多稳定性

Asymptotic Chow semistability implies Ding polystability for Gorenstein toric Fano varieties

本文证明了 Gorenstein 环面 Fano 簇的渐近 Chow 半稳定性蕴含关于环面测试构型的 Ding 多稳定性，推广了已有结果，并给出了 Mabuchi 常数的可加性公式及相对 K-稳定性与 Ding 稳定性差异的系统实例。

Doubling construction of Calabi-Yau fourfolds from toric Fano fourfolds

We give a differential-geometric construction of Calabi-Yau fourfolds by the `doubling' method, which was introduced in \cite{DY14} to construct Calabi-Yau threefolds. We also give examples of Calabi-Yau fourfolds from toric Fano fourfolds. Ingredients in our construction are \emph{admissible pairs}, which were first dealt with by Kovalev in \cite{K03}. Here in this paper an admissible pair $(\overline{X},D)$ consists of a compact Kähler manifold $\overline{X}$ and a smooth anticanonical divisor $D$ on $\overline{X}$. If two admissible pairs $(\overline{X}_1,D_1)$ and $(\overline{X}_2,D_2)$ wi…