John Lott
We give sufficient conditions for a noncompact Riemannian manifold, which has quadratic curvature decay, to have finite topological type with ends that are cones over spherical space forms.
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In a previous paper, we constructed complete manifolds of positive Ricci curvature with quadratically asymptotically nonnegative curvature and infinite topological type but dimension $\ge 6$. The purpose of the present paper is to use a different way to exhibit a family of complete $I$-dimensinal ($I\ge5$) Riemannian manifolds of positive Ricci curvature, quadratically asymptotically nonnegative sectional curvature, and certain infinite Betti number $b_j$ ($2\le j\le I-2$).
Four-dimensional homogeneous critical metrics for quadratic curvature functionals
本文确定了四维空间中所有使二次曲率泛函达到临界的齐次度量。
We give conditions which imply that a complete noncompact manifold with quadratic curvature decay has finite topological type. In particular, we find links between the topology of a manifold with quadractic curvature decay and some properties of the asymptotic cones of such a manifold.
We study rigidity results for the Einstein metrics as the critical points of a family of known quadratic curvature functionals involving the scalar curvature, the Ricci curvature and the Riemannian curvature tensor, characterized by some pointwise inequalities involving the Weyl curvature and the traceless Ricci curvature. Moreover, we also provide a few rigidity results for locally conformally flat critical metrics.
We study closed $n$-dimensional manifolds of which the metrics are critical for quadratic curvature functionals involving the Ricci curvature, the scalar curvature and the Riemannian curvature tensor on the space of Riemannian metrics with unit volume. Under some additional integral conditions, we classify such manifolds. Moreover, under some curvature conditions, the result that a critical metric must be Einstein is proved.
We construct a compact Kähler manifold of nonnegative quadratic bisectional curvature, which does not admit any Kähler metric of nonnegative orthogonal bisectional curvature. The manifold is a 7-dimensional Kähler C-space with second Betti number equal to 1, and its canonical metric is a Kähler-Einstein metric of positive scalar curvature
We show that there are topological obstructions for a noncompact manifold to admit a Riemannian metric with quadratic curvature decay and a volume growth which is slower than that of Euclidean space of the same dimension.
Sobolev Inequality In Manifolds With Lower Quadratic Curvature Decay
本文利用ABP方法，在具有下二次曲率衰减的完备黎曼流形中，为紧致区域和子流形建立了Sobolev不等式。
We are concerned with the study of different notions of curvature on graphs. We show that if a graph has stronger inner-outer curvature growth than a model graph, then it has faster volume growth too. We also study the relationhips of volume growth with other kind of curvatures, such as the Ollivier-Ricci curvature.
In this paper, we investigate a class of quadratic Riemannian curvature functionals on closed smooth manifold $M$ of dimension $n\ge 3$ on the space of Riemannian metrics on $M$ with unit volume. We study the stability of these functionals at the metric with constant sectional curvature as its critical point.
In this paper, we consider some rigidity results for the Einstein metrics as the critical points of some known quadratic curvature functionals on complete manifolds, characterized by some point-wise inequalities. Moreover, we also provide rigidity results by the integral inequalities involving the Weyl curvature, the trace-less Ricci curvature and the Sobolev constant, accordingly.
In this paper, we study Riemannian functionals defined by $L^2$-norms of Ricci curvature, scalar curvature, Weyl curvature, and Riemannian curvature. We try to understand stability of their critical points that are products of Einstein metrics. In particular, we prove that the product of a spherical space form and a compact hyperbolic manifold is unstable for some quadratic functionals if the first eigenvalue of the Laplacian of the hyperbolic manifold is sufficiently small.
In this paper, we prove some rigidity results for the Einstein metrics as the critical points of a family of known quadratic curvature functionals on closed manifolds, characterized by some point-wise inequalities. Moreover, we also provide a few rigidity results that involve the Weyl curvature, the trace-less Ricci curvature and the Yamabe invariant, accordingly.
Ricci solitons as critical points of quadratic curvature functionals
研究Ricci孤子作为特殊二次曲率泛函临界点的刚性，分析其与Einstein度量的关系。
In this paper, we construct a complete n-dim Riemannian manifold with positive Ricci curvature, quadratically nonnegatively curved infinity and infinite topological type. This gives a negative answer to a conjecture by Jiping Sha and Zhongmin Shen in the case of n greater than or equal to 6.
In this article we study compact K\ahler manifolds satisfying a certain nonnegativity condition on the bisectional curvature. Under this condition, we show that the scalar curvature is nonnegative and that the first Chern class is positive assuming local irreducibility. We also obtain a partial classification of possible de Rham decompositions of the universal cover under this condition
We use elementary methods to construct a minimal lamination of the interior of a positive cone in R3.
We prove that any complete metric on R^3 minus a ball with non-negative Ricci curvature and quadratic Ricci-curvature decay, has cubic volume growth.
This is a paper based on a talk given at the conference on Conformal Geometry which held at Roscoff in France in the 2008 summer. We study some aspects of the equation arising from the problem of the existence on a given closed Riemannian manifold of dimension at leat 4, of a conformal metric with constant $h_4$ curvature. We establish a simple formula relating the second Gauss-Bonnet curvature $h_4$ to the $σ_2$ curvature and we study some positivity properties of these two quadratic curvatures. We use different quadratic curvatures to characterize space forms, Einstein metrics and conformall…
In this paper we prove rigidity results on critical metrics for quadratic curvature functionals, involving the Ricci and the scalar curvature, on the space of Riemannian metrics with unit volume. It is well-known that Einstein metrics are always critical points. The purpose of this article is to show that, under some curvature conditions, a partial converse is true. In particular, for a class of quadratic curvature functionals, we prove that every critical metric with non-negative sectional curvature must be Einstein.
In this paper, we study the topology of complete noncompact Riemannian manifolds with asymptotically nonnegative Ricci curvature and large volume growth. We prove that they have finite topological types under some curvature decay and volume growth conditions. We also generize it to the manifolds with $k$-th asymptotically nonnegative Ricci curvature by using extensions of Abresch-Gromoll's excess function estimate.
In this paper, we obtain an Ecker-Huisken type result for entire graphs with parallel mean curvature.
In this article we give necessary and sufficient conditions for an irreducible Kähler C-space with $b_2=1$ to have nonnegative or positive quadratic bisectional curvature, assuming the space is not Hermitian symmetric. In the cases of the five exceptional Lie groups $E_6, E_7, E_8, F_4, G_2$, the computer package MAPLE is used to assist our calculations. The results are related to two conjectures of Li-Wu-Zheng.
Volume growth and positive scalar curvature
本文研究三维完备非紧黎曼流形在非负里奇曲率和一致正数量曲率条件下的体积增长，证明了尖锐线性增长比率并给出刚性刻画。
Positive Scalar Curvature and Volume Growth
针对非负里奇曲率的完备黎曼流形，通过证明两个精确体积增长阶估计，解决了格罗莫夫1986年提出的余维二体积增长猜想。
We give a new proof of a recent result of Munteanu--Wang relating scalar curvature to volume growth on a $3$-manifold with non-negative Ricci curvature. Our proof relies on the theory of $μ$-bubbles introduced by Gromov as well as the almost splitting theorem due to Cheeger--Colding.
Uniqueness of critical metrics for a quadratic curvature functional
研究二次曲率泛函临界度量的唯一性，证明在维数 $n\geq 10$ 时有限能量的完备临界度量必标量平坦，即为全局极小值。
In this paper we obtain three results concerning the geometry of complete noncompact positively curved Kähler manifolds at infinity. The first one states that the order of volume growth of a complete noncompact Kähler manifold with positive bisectional curvature is at least half of the real dimension (i.e., the complex dimension). The second one states that the curvature of a complete noncompact Kähler manifold with positive bisectional curvature decays at least linearly in the average sense. The third result is concerned with the relation between the volume growth and the curvature decay. We …
It is still an open problem that a complete open Kahler manifold with positive bisectional curvature is Stein. This paper partially resolve the problem by putting a restriction to volume growth condition. The partial solution here improves the observation in ([8], page 341). The improvement is based on assuming a weaker volume growth condition that is not sufficiently maximal.
Examples of open manifolds with almost quadratic volume growth and infinite Betti numbers
本文构造了具有正Ricci曲率、截面曲率下有界和无限Betti数的开流形示例，其体积增长可任意接近二次，并探讨了此类流形在至多二次体积增长下是否必须具有有限拓扑类型的问题。
Quadratic Scalar Curvature Decay and Uniform Positivity in Dimensions Four through Seven
针对四维至七维满足渐近二次标量曲率系数大于(n-1)/n的正标量曲率完备非紧黎曼流形，证明其存在标量曲率至少为1的完备光滑度量，证实了Gromov临界衰减速率猜想的对应部分。
In this article, we study properly immersed complete noncompact submanifolds in a complete shrinking gradient Ricci soliton with weighted mean curvature vector bounded in norm. We prove that such a submanifold must have polynomial volume growth under some mild assumption on the potential function. On the other hand, if the ambient manifold is of bounded geometry, we prove that such a submanifold must have at least linear volume growth. In particular, we show that a properly immersed complete noncompact hypersurface in the Euclidean space with bounded Gaussian weighted mean curvature must have …
Volume growth functions of complete Riemannian manifolds with positive scalar curvature
该研究针对维数不小于3的开流形是否存在与给定函数同增长类型体积增长的正数量曲率度量这一问题，利用Gromov-Lawson和Grimaldi-Pansu构造，证明了闭流形无穷连通和情形下结论成立，并推广至沿低维球面的无穷连通和情形。
Lower bounds on Ricci curvature limit the volumes of sets and the existence of harmonic functions on Riemannian manifolds. In 1975, Shing Tung Yau proved that a complete noncompact manifold with nonnegative Ricci curvature has no nonconstant harmonic functions of sublinear growth. In the same paper, Yau used this result to prove that a complete noncompact manifold with nonnegative Ricci curvature has at least linear volume growth. In this paper, we prove the following theorem concerning harmonic functions on these manifolds. Theorem: Let M be a complete noncompact manifold with nonnegative Ric…
Curvature-free effects from volume growth and ends-counting and their applications
本文研究了体积增长和端计数的无曲率效应，建立了两个主要定理，并应用于Calabi-Yau极小体积增长定理和Cai-Li-Tam有限端定理的证明，不依赖Bishop-Gromov体积比较定理或Ricci曲率专用分析工具。
Volume growth and integral curvature bound for non-negatively curved three-manifolds
本文研究三维非负曲率流形，证明欧氏体积增长等价于平均二次曲率衰减，并给出基于标量曲率积分阈值的判定及间隙定理。
Weitzenböck-Bochner-Kodaira formulas with quadratic curvature terms
本文在紧 Kähler 流形上建立含二次曲率项的新型 Bochner-Kodaira 公式，并推导 Riemannian 与 Kähler 情形下的 Weitzenböck 公式，从而获得弱曲率条件下的消没定理与 Hodge 数估计。
New Rigidity Results for Critical Metrics of Some Quadratic Curvature Functionals
本文研究闭光滑流形上二次曲率泛函 $\mathfrak{F}_{t}$ 的临界度量，在截面曲率拼挤条件下证明新刚性，并推出四维 Bach 平坦常标量曲率度量的 Einstein 性与标准分类。
On perimeter minimizing sets in manifolds with quadratic volume growth
本文研究黎曼流形中周长极小化集合对等距分裂的影响，证明非负截面曲率且无穷远二次体积增长的流形会因该集合存在发生等距分裂，且其边界对应乘积结构中的切片。
Critical metrics for the quadratic curvature functional on complete four-dimensional manifolds
本文研究了四维完备流形上曲率泛函的临界度量，证明其要么为爱因斯坦流形，要么局部等距于常曲率积空间。
Curvature growth and holomorphic splitting for Kähler metrics with cone singularities
本文研究锥角在1/2到1之间的Kähler度量，证明除子附近有界曲率导致法丛全纯分裂，证实Donaldson的猜想。
On manifolds with nonnegative Ricci curvature and the infimum of volume growth order $<2$
本文针对具有非负Ricci曲率且体积增长阶下确界小于2的开流形，证明了两个刚性定理：万有覆盖具有欧氏体积增长等价于流形平坦且具有n-1维soul；存在非常值线性增长调和函数等价于流形等距同构于实数线与紧流形的度量积。
We investigate the $L^p$-boundness of the Riesz transform on Riemannian manifolds whose Ricci curvature has quadratic decay. Two criteria for the $L^p$-unboundness of the Riesz transform are given. We recover known results about manifolds that are Euclidean or conical at infinity.
We consider complete noncompact Riemannian manifolds with quadratically decaying lower Ricci curvature bounds and minimal volume growth. We first prove a rigidity result showing that ends with strongly minimal volume growth are isometric to warped product manifolds. Next we consider the almost rigid case in which manifolds with nonnegative and quadratically decaying lower Ricci curvature bounds have minimal volume growth. Compact regions in such manifolds are shown to be asymptotically close to warped products in the Gromov-Hausdorff topology. Manifolds with nonnegative Ricci curvature and lin…
We study mean curvature flow in $\mathbb S_K^{n+1}$, the round sphere of sectional curvature $K>0$, under the quadratic curvature pinching condition $|A|^{2} < \frac{1}{n-2} H^{2} + 4 K$ when $n\ge 4$ and $|A|^{2} < \frac{3}{5}H^{2}+\frac{8}{3}K$ when $n=3$. This condition is related to a famous theorem of Simons, which states that the only minimal hypersurfaces satisfying $\vert A\vert^2<nK$ are the totally geodesic hyperspheres. It is related to but distinct from two-convexity. Notably, in contrast to two-convexity, it allows the mean curvature to change sign. We show that the pinching condi…
Ancient solutions of the Ricci flow arise naturally as models for singularity formation. There has been significant progress towards the classification of such solutions under natural geometric assumptions. Nonnegatively curved solutions in dimensions 2 and 3, and uniformly PIC solutions in higher dimensions are now well understood. We consider ancient solutions of arbitrary dimension which are complete and have Type~I curvature growth. We show that a $κ$-noncollapsed Type~I ancient solution which is noncompact and has nonnegative sectional curvature necessarily splits at least one Euclidean f…
Optimal volume bound and volume growth for Ricci-nonnegative manifolds with positive Bi-Ricci curvature
本文在维数小于八的条件下，证明了具有非负Ricci曲率且紧集外双Ricci曲率下界为n-2的完备黎曼流形的最优体积增长，回答了Antonelli-Xu的问题，并给出正双Ricci曲率下Gromov体积界猜想的类比。
Suppose $(M,g)$ is a Riemannian manifold having dimension $n$, nonnegative Ricci curvature, maximal volume growth and unique tangent cone at infinity. In this case, the tangent cone at infinity $C(X)$ is an Euclidean cone over the cross-section $X$. Denote by $α=\lim_{r\rightarrow\infty}\frac{\mathrm{Vol}(B_{r}(p))}{r^{n}}$ the asymptotic volume ratio. Let $h_{k}=h_{k}(M)$ be the dimension of the space of harmonic functions with polynomial growth of growth order at most $k$. In this paper, we prove a upper bound of $h_{k}$ in terms of the counting function of eigenvalues of $X$. As a corollary…
Minimal Degrees, Volume Growth, and Curvature Decay on Complete Kähler Manifolds
本文研究了完备凯勒流形上非负双曲率的最小次数、体积增长与曲率衰减之间的关系，通过多项式增长的全纯函数和全纯体积形式建立了精确联系，并描述了凯勒-里流形的李雅普诺夫渐进行为，统一了刘和曹-李-Tam的两种证明方法，解决了杨的两个猜想。
Complete 3-manifolds of positive scalar curvature with quadratic decay
本文证明具有正数量曲率且无穷远处次二次衰减的完备可定向3-流形可分解为球面流形与S²×S¹的连通和，推广了Gromov-Wang定理并部分回答了Gromov猜想，且该衰减速率是最优的。
We study mean curvature flow of $n$-dimensional submanifolds of $S_K^{n+\ell}$, the round $(n+\ell)$-sphere of sectional curvature $K>0$, under the quadratic curvature pinching condition $|A|^{2} < \frac{1}{n-2}|H|^{2} + 4K$ when $n\geq 8$, $|A|^{2} < \frac{4}{3n}|H|^{2}+\frac{n}{2}K$ when $n=7$, and $|A|^2<\frac{3(n+1)}{2n(n+2)}|H|^2+\frac{2n(n-1)}{3(n+1)}K$ when $n=5$ or $6$. This condition is related to a theorem of Li and Li [Arch. Math., 58:582--594, 1992] which states that the only $n$-dimensional minimal submanifolds of $S_K^{n+\ell}$ satisfying $|A|^2<\frac{2n}{3}K$ are the totally geo…
Fundamental groups of open manifolds with nonnegative Ricci curvature and universal cover Euclidean volume growth
本研究针对非负Ricci曲率开流形的基本群性质问题，证明了万有覆叠具欧氏体积增长时基本群有限生成且实质上阿贝尔，还将有限生成结论推广到更一般条件，肯定了Pan-Rong猜想。
In 1968, Milnor conjectured that a complete noncompact manifold with nonnegative Ricci curvature has a finitely generated fundamental group. The author applies the Excess Theorem of Abresch and Gromoll (1990), to prove two theorems. The first states that if such a manifold has small linear diameter growth then its fundamental group is finitely generated. The second states that if such a manifold has an infinitely generated fundamental group then it has a tangent cone at infinity which is not polar. A corollary of either theorem is the fact that if such a manifold has linear volume growth, then…
We exhibit a curious link between the Quadratic Orthogonal Bisectional Curvature, combinatorics, and distance geometry. The Weitzenböck curvature operator, acting on real (1,1)--forms, is realized as the Dirichlet energy of a finite graph, weighted by a matrix of the curvature. These results also illuminate the difference in the nature of the Quadratic Orthogonal Bisectional Curvature and the Real Bisectional Curvature.
Let $(M, g)$ be a complete non-compact Kähler manifold with non-negative and bounded holomorphic bisectional curvature. Extending our techniques developed in \cite{CT3}, we prove that the universal cover $\wt M$ of $M$ is biholomorphic to $\ce^n$ provided either that $(M, g)$ has average quadratic curvature decay, or $M$ supports an eternal solution to the Kähler-Ricci flow with non-negative and uniformly bounded holomorphic bisectional curvature. We also classify certain local limits arising from the Kähler-Ricci flow in the absence of uniform estimates on the injectivity radius.
Let $M$ be a complete Kähler manifold with nonnegative bisectional curvature. Suppose the universal cover does not split and $M$ admits a nonconstant holomorphic function with polynomial growth, we prove $M$ must be of maximal volume growth. This confirms a conjecture of Ni. There are two essential ingredients in the proof: The Cheeger-Colding theory on Gromov-Hausdorff convergence of manifolds; the three circle theorem for holomorphic functions.
We obtain a Calabi-Yau type lower volume growth estimates for complete noncompact self-shrinkers of the mean curvature flow, more precisely, every complete noncompact properly immersed self-shrinker has at least linear volume growth.
This is our second paper in a series to study gravitational instantons, i.e. complete hyperkäler 4-manifolds with faster than quadratic curvature decay. We prove two main theorems: 1.The asymptotic rate of gravitational instantons to the standard models can be improved automatically. 2.Any ALF-D_k gravitational instanton must be the Cherkis-Hitchin-Ivanov-Kapustin-Lindström-Roček metric.
In this paper, we study gravitational instantons (i.e., complete hyperkäler 4-manifolds with faster than quadratic curvature decay). We prove three main theorems: 1.Any gravitational instanton must have known end----ALE, ALF, ALG or ALH. 2.In ALG and ALH-non-splitting cases, it must be biholomorphic to a compact complex elliptic surface minus a divisor. Thus, we confirm a long-standing question of Yau in ALG and ALH cases. 3.In ALF-D_k case, it must have an O(4)-multiplet.
We make some improvements to our previous results. First, we prove a version of our volume growth theorem which does not require any assumption on the first Betti number. Second, we show that our local regularity theorem only requires a lower volume growth assumption, not a full Sobolev constant bound. These results allow us to weaken the assumptions of our previous volume growth and convergence theorems.
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