Chengjie Yu, Feifei Zhao
In this paper, we obtain Li-Yau type gradient estimates with time dependent parameter for positive solutions of the heat equation that are different with the estimates by Li-Xu \cite{LX} and Qian \cite{Qi}. As an application of the estimate, we also obtained improvements of Davies' Li-Yau type gradient estimate.
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Some aspects of Cheng-Yau gradient estimates
本文扩展了Cheng-Yau梯度估计的刚性，应用于具有下界里奇曲率的曲面，并获得了高维Riemannian流形上的点wise梯度估计及正调和函数的单调性公式。
We improve the well known local gradient estimate of Cheng and Yau in the case when Ricci curvature has a negative lower bound.
We show that, up to the flow of the soliton vector field, there exists a unique complete steady gradient Kähler-Ricci soliton in every Kähler class of an equivariant crepant resolution of a Calabi-Yau cone converging at a polynomial rate to Cao's steady gradient Kähler-Ricci soliton on the cone.
This article is devoted to the study of several estimations for a positive solution to a nonlinear weighted parabolic equation on a weighted Riemannian manifold. We therefore derive new Li-Yau type and Hamilton type gradient estimates yielding several consequences. We also derive Hessian estimate and some corollaries for the same equation. Among the applications of our estimates discussed here are Harnack type inequalities, Liouville type theorems and a local time reversed Harnack inequality.
This note studies the equivalencies among convergences of Ricci-flat Kähler-Einstein metrics on Calabi-Yau manifolds, cohomology classes and potential functions.
A Li-Yau gradient estimate for the Finslerian logarithmic Schrödinger equation
该研究借助新的拉普拉斯比较定理，在混合加权Ricci曲率有下界的非紧完备芬斯勒流形上，推导了含时系数的芬斯勒对数薛定谔方程的Li-Yau型梯度估计，并得到其正解的Harnack不等式与先验估计。
Sharp gradient estimate and Yau's Liouville theorem for the heat equation on noncompact manifolds
我们得到一个尖锐的，局部化的版本的椭圆型梯度估计的正解（有界或无界）的热方程。这些估计类似于拉普拉斯方程的Cheng-Yau估计和紧致流形上热方程有界解的Hamilton估计。作为应用，在一定的增长条件下，我们将丘氏著名的关于正调和函数的Liouville定理推广到热方程的正永恒解。令人惊讶的是，即使在没有这样的条件的${\bf R}^n$中，热方程的刘维尔定理也不成立。我们还证明了非紧流形上热核对数的一个锐化的长时间梯度估计。这一直是一个开放的问题，在紧凑，短时间的情况下，众所周知的估计。
Let $(\M^n, g_{ij})$ be a complete Riemammnian manifold. For some constants $p,\ r>0$, define $\displaystyle k(p,r)=\sup_{x\in M}r^2\left(\oint_{B(x,r)}|Ric^-|^p dV\right)^{1/p}$, where $Ric^-$ denotes the negative part of the Ricci curvature tensor. We prove that for any $p>\frac{n}{2}$, when $k(p,1)$ is small enough, certain Li-Yau type gradient bound holds for the positive solutions of the heat equation on geodesic balls $B(O,r)$ in $\M$ with $0<r\leq 1$. Here the assumption that $k(p,1)$ being small allows the situation where the manifolds is collapsing. Recall that in \cite{ZZ}, certain L…
Li-Yau sub-gradient estimates and Perelman-type entropy formulas for the heat equation in quaternionic contact geometry
本文在紧致四元数接触流形上建立qc热方程的Li-Yau型次梯度估计，并在qc-爱因斯坦流形上推导Perelman型熵公式，推广了经典黎曼几何结果。
We prove Li-Yau type gradient bounds for the heat equation either on manifolds with fixed metric or under the Ricci flow. In the former case the curvature condition is $|Ric^-| \in L^p$ for some $p>n/2$, or $\sup_\M \int_\M |Ric^-|^2(y)d^{2-n}(x,y)dy<\infty$, where $n$ is the dimension of the manifold. In the later case, one only needs scalar curvature being bounded. We will explain why the conditions are nearly optimal and give an application. The Li-Yau bound for the heat equation on manifolds with fixed metric seems to be the first one allowing Ricci curvature not bounded from below.
In this paper, motivated by finding sharp Li-Yau type gradient estimate for positive solution of heat equations on complete Riemannian manifolds with negative Ricci curvature lower bound, we first introduce the notion of Li-Yau multiplier set and show that it can be computed by heat kernel of the manifold. Then, an optimal Li-Yau type gradient estimate is obtained on hyperbolic spaces by using recurrence relations of heat kernels on hyperbolic spaces. Finally, as an application, we obtain sharp Harnack inequalities on hyperbolic spaces.
In this note we show how results in \cite{BaudoinBonnefont2016, BaudoinGarofalo2013, CoulhonJiangKoskelaSikora2017} yield the Cheng-Yau estimate on two classes of sub-Riemannian manifolds: Carnot groups and sub-Riemannian manifolds satisfying a generalized curvature-dimension inequality.
In this paper, we obtain a Li-Yau type gradient estimate with time dependent parameter for positive solutions of the heat equation, so that the Li-Yau type gradient estimate of Li-Xu are special cases of the estimate. We also obtain improvements of Davies' Li-Yau type gradient estimate. The argument is different with those of Li-Xu and Qian.
We prove the Bochner-Weitzenböck formula for the (nonlinear) Laplacian on general Finsler manifolds and derive Li-Yau type gradient estimates as well as parabolic Harnack inequalities. Moreover, we deduce Bakry-Émery gradient estimates. All these estimates depend on lower bounds for the weighted flag Ricci tensor.
In this paper, motivated by the work of Qi S. Zhang in [28], we derive Li-Yau gradient bounds for positive solutions of the f-heat equation on closed manifolds with Bakry-Emery Ricci curvature bounded below.
In this paper, motivated by the works of Bakry et. al in finding sharp Li-Yau type gradient estimate for positive solutions of the heat equation on complete Riemannian manifolds with nonzero Ricci curvature lower bound, we first introduce a general form of Li-Yau type gradient estimate and show that the validity of such an estimate for any positive solutions of the heat equation reduces to the validity of the estimate for the heat kernel of the Riemannian manifold. Then, a sharp Li-Yau type gradient estimate on the three dimensional hyperbolic space is obtained by using the explicit expression…
In this paper, on Riemannian manifolds with boundary, we establish a Yau type gradient estimate and Liouville theorem for harmonic functions under Dirichlet boundary condition. Under a similar setting, we also formulate a Souplet-Zhang type gradient estimate and Liouville theorem for ancient solutions to the heat equation.
We prove differential Harnack inequalities for flows of strictly convex hypersurfaces by powers $p$, $0<p<1$, of the mean curvature in Einstein manifolds with a positive lower bound on the sectional curvature. We assume that this lower bound is sufficiently large compared to the derivatives of the curvature tensor of the ambient space and that the mean curvature of the initial hypersurface is sufficiently large compared to the ambient geometry. We also obtain some new Harnack inequalities for more general curvature flows in the sphere, as well as a monotonicity estimate for the mean curvature …
In this paper, we generalize the Cao-Yau's gradient estimate for the sum of squares of vector fields up to higher step under assumption of the generalized curvature-dimension inequality. With its applications, by deriving a curvature-dimension inequality, we are able to obtain the Li-Yau gradient estimate for the CR heat equation in a closed pseudohermitian manifold of nonvanishing torsion tensors. As consequences, we obtain the Harnack inequality and upper bound estimate for the CR heat kernel.
In this paper, we establish a Bochner type formula on Alexandrov spaces with Ricci curvature bounded below. Yau's gradient estimate for harmonic functions is also obtained on Alexandrov spaces.
This article shows that if the negative part of Ricci curvature lies in the Kato class, the heat kernel satisfies a Li-Yau type estimate. Additionally, using the resulting heat kernel bound, we show that the obtained heat kernel estimate leads to bounds on the first Betti number only depending on the Kato constant.
Lagrangian torus fibration of quintic Calabi-Yau hypersurfaces II: Technical results on gradient flow construction
本文提供了梯度流构造的技术细节和相关问题，这对于我们构造Calabi-Yau超曲面的Lagrange环面纤维化是必不可少的。
Matrix Li-Yau-Hamilton estimates for the heat equation on Kaehler manifolds
证明了具有非负对分曲率的完备Kaehler流形上热方程正解的矩阵Li-Yau-Hamilton型梯度估计。作为结果，我们得到了比较定理的距离函数下的曲率假设。
A note on Perelman's LYH inequality
给出了Perelman关于共轭热方程基本解的Li-Yau-Hamilton型不等式的一个证明.本文的其余部分致力于通过单调性公式改进已知的Li-Yau-Hamilton型微分不等式。
We prove a Li-Yau gradient estimate for positive solutions to the heat equation, with Neumann boundary conditions, on a compact Riemannian submanifold with boundary ${\bf M}^n\subseteq {\bf N}^n$, satisfying the integral Ricci curvature assumption: \begin{equation} D^2 \sup_{x\in {\bf N}} \left( \oint_{B(x,D)} |Ric^-|^p dy \right)^{\frac{1}{p}} < K \end{equation} for $K(n,p)$ small enough, $p>n/2$, where $diam({\bf M})\leq D$. The boundary of ${\bf M}$ is not necessarily convex, but it needs to satisfy the interior rolling $R-$ball condition.
Inspired Yau's work (Comm. Anal. Geom., 1994), in this short note we provide a new version of Li-Yau gradient estimate for the linear heat equation, which generalizes some known results and gives new gradient estimates. Also we explain the different known results as different cases here.
In this paper, we consider the gradient estimates of the positive solutions to the following equation defined on a complete Riemannian manifold $(M, g)$ $$Δu + au(\log u)^{p}+bu=0,$$ where $a, b\in \mathbb{R}$ and $p$ is a rational number with $p=\frac{k_1}{2k_2+1}\geq2$ where $k_1$ and $k_2$ are positive integer numbers. we obtain the gradient bound of a positive solution to the equation which does not depend on the bounds of the solution and the Laplacian of the distance function on $(M, g)$. Our results can be viewed as a natural extension of Yau's estimates on positive harmonic function.
This is a short expository note about Calabi-Yau manifolds and degenerations of their Ricci-flat metrics.
Duistermaat-Heckman formula for a torus action on a generalized Calabi-Yau manifold and localization formula
本说明是对我们早期工作\cite{humi}的补充。在\cite{humi}中，我们研究了广义Calabi-Yau流形的Hamilton作用，证明了Duistermaat-Heckman定理成立.本文的目的是证明Duistermaa-Heckman测度的密度函数是一个分段多项式。我们还证明了本地化公式成立。
We derive a gradient estimate for positive functions, in particular for positive solutions to the heat equation, on finite or locally finite graphs. Unlike the well known Li-Yau estimate, which is based on the maximum principle, our estimate follows from the graph structure of the gradient form and the Laplacian operator. Though our assumption on graphs is slightly stronger than that of Bauer, Horn, Lin, Lippner, Mangoubi, and Yau (J. Differential Geom. 99 (2015) 359-405), our estimate can be easily applied to nonlinear differential equations, as well as differential inequalities. As applicati…
Miyaoka-Yau inequality for minimal projective manifolds of general type
本文利用Kähler-里奇流证明了一般型极小射影$n$ -流形的Miyaoka-Yau不等式.
Calabi-Yau coverings over some singular varieties and new Calabi-Yau 3-folds with Picard number one
本文是关于某些奇异簇容许Calabi-Yau覆盖的观察的报告。作为应用，我们构造了18个新的Picard数为1的Calabi-Yau 3-折叠，它们具有一些有趣的性质.
Wang and Yau [10] introduced a quasi-local mass, which is a hyperbolic background generalization of Liu-Yau's expression [7] [8], and proved its positivity. In this note, we prove that the positivity of this quasi-local mass is still valid under weaker assumptions on the boundary hypersurface in general dimensions. The method we used is similar to that used by Eichmair, Miao and Wang in [4].
In this note we construct Mabuchi $\mathcal{L}^{\rm M}_ω$ functional and Aubin-Yau functionals $\mathcal{I}^{\rm AY}_ω, \mathcal{J}^{\rm AY}_ω$ on any compact complex surfaces, and establish a number of properties. Our construction coincides with the original one in the Kähler case.
A remark on the second order estimates for the quaternionic Calabi-Yau problem on hyperkähler manifolds
本文通过简化方法重新审视超kähler流形上四元数Calabi-Yau问题的二次估计，提出更简洁的推导方式。
In this short note, we offer an observation that the Miyaoka-Yau inequality holds for any compact Kähler manifold with nef canonical bundle, i.e. a smooth minimal model. It follows directly from the existence of cscK metrics in a neighborhood of the canonical class which was confirmed both by the work of Dyrefelt and Song using different approaches.
Uniform estimates: from Yau to Kolodziej
本文提出一种新颖高效的方法，用于建立复 Monge–Ampère 方程及满足行列式型控制的几何 PDE 解的一致估计。
Yau-type gradient estimates for p-harmonic functions on Riemannian manifolds with boundary under Dirichlet boundary condition
本文在带边黎曼流形上，利用边界径向障碍与内部最大值原理，将Yau型梯度估计推广至p-调和函数，并导出Liouville定理。
In this paper, we study Li-Yau gradient estimates for the solutions $u$ to the heat equation $\partial_tu=Δu$ on graphs under the curvature condition $CD(n,-K)$ introduced by Bauer et al. in \cite{BHLLMY}. As applications, we derive Harnack inequalities and heat kernel estimates on graphs. Also we present a type of Hamilton gradient estimates.
Cheng-Yau logarithmic gradient estimates for a nonlinear elliptic equation on smooth metric measure spaces
本文在m-Bakry-Émery Ricci曲率有下界的完备光滑测度空间上，利用Nash-Moser迭代技术研究非线性椭圆方程，获得了正解的局部梯度估计，并推导出Liouville型定理和Harnack不等式，推广并改进了已有结果。
The asymptotic behavior of the steady gradient Kähler-Ricci soliton of the Taub-NUT type of Apostolov and Cifarelli
本文确定了Apostolov-Cifarelli的Taub-NUT型稳态梯度Kähler-Ricci孤立子的渐近锥，证明其特例为ALF Calabi-Yau度量，并用Tian-Yau-Hein方法构造了新的ALF Calabi-Yau度量。
Continuing our previous work (arXiv:1509.07981v1), we derive another global gradient estimate for positive functions, particularly for positive solutions to the heat equation on finite or locally finite graphs. In general, the gradient estimate in the present paper is independent of our previous one. As applications, it can be used to get an upper bound and a lower bound of the heat kernel on locally finite graphs. These global gradient estimates can be compared with the Li-Yau inequality on graphs contributed by Bauer, Horn, Lin, Lipper, Mangoubi and Yau (J. Differential Geom. 99 (2015) 359-4…
Singular Calabi-Yau metrics
本文为CIME暑期学校讲义，系统综述了近十五年来多位作者在Hermitian背景下关于复Monge-Ampère方程的研究成果。
In this paper, we will study the (linear) geometric analysis on metric measure spaces. We will establish a local Li-Yau's estimate for weak solutions of the heat equation and prove a sharp Yau's gradient gradient for harmonic functions on metric measure spaces, under the Riemannian curvature-dimension condition $RCD^*(K,N).$
In this note, using the recent compactness results of Tian and Chen-Donaldson-Sun, we prove the K-semistable version of Yau-Tian-Donaldson correspondence for Fano manifolds.
We study an equation proposed by Fu and Yau as a natural $n$-dimensional generalization of a Strominger system that they solved in dimension $2$. It is a complex Hessian equation with right hand side depending on gradients. Building on the methods of Fu and Yau, we obtain $C^0$, $C^2$ and $C^{2,α}$ a priori estimates. We also identify difficulties in extending the Fu-Yau arguments for non-degeneracy from dimension $2$ to higher dimensions.
In this note, a gradient estimate for the complex Monge-Ampere equation is established. It differs from previous estimates of Yau, Hanani, Blocki, P. Guan, B. Guan - Q. Li in that it is pointwise, and depends only on the infimum of the solution instead of its $C^0$ norm.
In this note we give an overview of some applications of the Calabi-Yau theorem to the construction of singular positive (1,1) currents on compact complex manifolds. We show how recent developments allow us to give streamlined proofs of existing results, as well as new ones.
Calabi-Yau threefolds across quadratic singularities
本文基于MATRIX项目讲义，回顾Calabi-Yau几何基础，描述锥形流形变换的拓扑特征，并综述其几何化的最新进展。
Operators on nonlinear metric measure spaces I: A New Laplacian comparison theorem on Finsler manifolds and a generalized Li-Yau approach to gradient estimates of Finslerian Schrödinger equation
本文在 Finsler 流形上引入混合加权 Ricci 曲率并证明新的 Laplacian 比较定理，据此建立 Finsler Schrödinger 方程正解的整体与局部 Li-Yau 型梯度估计。
We will give a simple proof that the metric of any compact Yamabe gradient soliton (M,g) is a metric of constant scalar curvature when the dimension of the manifold n>2.
In the present notes we explain the relationship between Calabi-Yau integrable systems and Hitchin systems based on work by Diaconescu-Donagi-Pantev and the author. Besides a review of these integrable systems, we highlight related topics, for example variations of Hodge structures, cameral curves and Slodowy slices, along the way.
The rigidity and stability of gradient estimates
本文研究非负曲率空间上的梯度估计问题，得到了Cheng-Yau、Li-Yau等经典精确梯度估计及Dirichlet格林函数相关估计的刚性结论，并进一步给出了对应的稳定性结果。
Feasibility of Nash-Moser iteration for Cheng-Yau-type gradient estimates of nonlinear equations on complete Riemannian manifolds
该研究利用Nash-Moser迭代技术，给出了完备黎曼流形上广义非线性Poisson方程正解满足Cheng-Yau型梯度估计的条件，推广了多种拉普拉斯算子情形，并证明了相关Harnack不等式与Liouville定理。
Motivated by the results of Wu-Yau-Zheng \cite{WuYauZheng}, we show that under a certain curvature assumption the harmonic representative of any boundary class of the Kähler cone is nonnegative.
We prove a priori estimates for a generalised Monge-Ampère PDE with "non-constant coefficients" thus improving a result of Sun in the Kähler case. We apply this result to the deformed Hermitian Yang-Mills (dHYM) equation of Jacob-Yau to obtain an existence result and a priori estimates for some ranges of the phase angle assuming the existence of a subsolution. We then generalise a theorem of Collins-Szèkelyhidi on toric varieties and use it to address a conjecture of Collins-Jacob-Yau.
In this note we show that if a compact Kahler manifold with trivial canonical bundle is the total space of a holomorphic fibration without singular fibers, then the fibration is a holomorphic fiber bundle. In the algebraic case, the fibration becomes trivial after a finite base change.
In this note, we study the SYZ mirror construction for a toric Calabi-Yau manifold using instanton corrections coming from Woodward's quasimap Floer theory instead of Fukaya-Oh-Ohta-Ono's Lagrangian Floer theory. We show that the resulting SYZ mirror coincides with the one written down via physical means (as expected).
A note on the supercritical deformed Hermitian-Yang-Mills equation
该研究针对超临界形变Hermitian-Yang-Mills方程，证明紧Kähler流形上有解的实(1,1)类是满足Collins-Jacob-Yau数值条件的类的既开又闭真子集，推翻了Collins-Jacob-Yau的相关猜想。
In this note, we obtain existence results for complete Ricci-flat Kahler metrics on crepant resolutions of singularities of Calabi-Yau varieties. Furthermore, for certain asymptotically flat Calabi-Yau varieties, we show that the Ricci-flat metric on the resolved manifold has the same asymptotic behavior as the initial variety.
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