Invariant Measures and Lower Ricci Curvature Bounds

Potential Analysis - Given a metric measure space $(X,d,mathfrak {m})$ that satisfies the Riemannian Curvature Dimension condition, RCD?(K,N), and a compact subgroup of isometries G ≤...     

Pseudolocality of the Ricci Flow Under Integral Bound of Curvature

We prove a pseudolocality type theorem for compact Ricci flows under local integral bounds on curvature. The main tool we use here is the local Ricci flow introduced by Deane Yang and the pseudolocality theorem due to Perelman. We also prove a theorem on the extension of the local Ricci flow.     

On Generalized Measure Contraction Property and Energy Functionals over Lipschitz Maps

We construct Sobolev spaces and energy functionals over maps between metric spaces under the strong measure contraction property of Bishop–Gromov type, which is a generalized notion of Ricci curvature bounded below. We also present the notion of generalized measure contraction property, which gives a characterization of energies by approximating energies of Sturm type over Lipschitz maps.     

On the Lower Bound of the Hausdorff Measure of the Koch Curve

This paper gives a lower bound of the Hausdorff measure of the Koch curve by means of the mass distribution principle.     

A Rigidity Theorem for Compact Hypersurfaces with an Upper Bound for the Ricci Curvature

We focus our attention on compact hypersurfaces with Ricci curvature bounded from above and we give a sufficient condition for them to be spherical. This generalizes and completes previous results.     

有非负Ricci曲率的度量测度空间上调和函数的边界问题

设(X,d,μ)是满足非负Ricci曲率条件的度量测度空间.本文研究了(开)上半空间X×R+上调和函数的边界问题.我们得到了:若u(x,t)是定义在上半空间X×R+上的调和函数,且满足Carleson测度条件supxB,rB∫rB0fB(xB,rB)|t▽u(x,t)|2dμ(x)dt/t≤C＜∞,其中▽=(▽x,?)...     

Ricci Curvature and Fundamental Group

By refined volume estimates in terms of Ricci curvature, the two results due to J. Milnor (1968) are generalized.     

余辛流形的半不变子流形的Ricci曲率

本文研究了余辛流形的半不变子流形,得到了这类子流形的Ricci曲率与平均曲率平方之间的—个不等式,并讨论了等式成立的充分必要条件．     

小Excess与具负下界Ricci曲率开流形的拓扑

In this paper,we study the relation between the excess of open manifolds and their topology by using the methods of comparison geometry.We prove that a complete open Riemmannian manifold with Ricci curvature negatively lower bounded is of finite topological type provided that the conjugate radius is bounded from below by a positive constant and its Excess is bounded by some function of its conjugate radius,which improves some results in [4].     

Ricci Curvature Decay on Open Manifolds

The behaviour of the Ricci curvature along rays in a completeopen manifold is examined.     

常曲率空间中具正Ricci曲率的子流形

设S~(n+p)(1)是一单位球面,M~n是浸入S~(n+p)(1)的具有非零平行平均曲率向量的n维紧致子流形.证明了当n≥4,p≥2时,如果M~n的Ricci曲率不小于(n-2)(1+H~2),则M~n是全脐的或者M~n的Ricci曲率等于(n-2)(1+H~2),进而M~n的几何分类被完全给出.     

Complete Open Manifolds with Nonnegative Ricci Curvature

In this paper, we study complete open manifolds with nonnegative Ricci curvature and injectivity radius bounded from below. We find that this kind of manifolds are diffeomorphic to a Euclidean space when certain distance functions satisfy a reasonable condition.     

On the Ricci Curvature of Compact Spacelike Hypersurfaces in de Sitter Space

In this paper we establish a sufficient condition for a compact spacelike hypersurface in de Sitter space to be spherical in terms of a pinching condition for the Ricci curvature. Our result will be a consequence of an integral formula involving the Ricci curvature and the scalar curvature of the hypersurface. We also derive some other consequences and applications of this formula.     

Curvature estimates for the Ricci flow I

In this paper we present several curvature estimates for solutions of the Ricci flow and the modified Ricci flow (including the volume normalized Ricci flow and the normalized Kähler-Ricci flow), which depend on the smallness of certain local \(L^{\frac{n}{2}}\) integrals of the norm of the Riemann curvature tensor |Rm|, where n denotes the dimension of themanifold. These local integrals are scaling invariant and very natural.     

Curvature estimates for the Ricci flow II

In this paper we present several curvature estimates and convergence results for solutions of the Ricci flow, including the volume normalized Ricci flow and the normalized Kähler-Ricci flow. The curvature estimates depend on smallness of certain local space-time integrals of the norm of the Riemann curvature tensor, while the convergence results require finiteness of space-time integrals of this norm. These results also serve as characterization of blow-up singularities.     

A Note on Lower Bounds Estimates for the Neumann Eigenvalues of Manifolds with Positive Ricci Curvature

We study new heat kernel estimates for the Neumann heat kernel on a compact manifold with positive Ricci curvature and convex boundary. As a consequence, we obtain lower bounds for the Neumann eigenvalues which are consistent with Weyl??s asymptotics.     

关于对数平均的上界和下界

本文指出关于对数平均的上界的一项研究工作中存在的错误,并且给出对数平均的一些更精密的上界和下界.     

Ricci Curvature and Bochner Formulas for Martingales

We generalize the classical Bochner formula for the heat flow on M to martingales on the path space PM and develop a formalism to compute evolution equations for martingales on path space. We see that our Bochner formula on PM is related to two‐sided bounds on Ricci curvature in much the same manner that the classical Bochner formula on M is related to lower bounds on Ricci curvature. Using this formalism, we obtain new characterizations of bounded Ricci curvature, new gradient estimates for martingales on path space, new Hessian estimates for martingales on path space, and streamlined proofs of the previous characterizations of bounded Ricci curvature.© 2018 Wiley Periodicals, Inc.