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Nonclassical minimizing surfaces with smooth boundary 具有光滑边界的非经典最小化曲面
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-06-22 DOI: 10.4310/jdg/1669998183
Camillo De Lellis, G. Philippis, J. Hirsch
We construct a Riemannian metric $g$ on $mathbb{R}^4$ (arbitrarily close to the euclidean one) and a smooth simple closed curve $Gammasubset mathbb R^4$ such that the unique area minimizing surface spanned by $Gamma$ has infinite topology. Furthermore the metric is almost Kahler and the area minimizing surface is calibrated.
我们在$mathbb{R}^4$上构造了一个黎曼度量$g$(任意接近欧几里德度量$g$)和一个光滑的简单闭曲线$Gamma子集mathbb R^4$,使得$Gamma$张成的唯一面积最小化曲面具有无限拓扑。此外,度量几乎是Kahler,面积最小曲面被校准。
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引用次数: 6
Global Nash–Kuiper theorem for compact manifolds 紧致流形的全局Nash-Kuiper定理
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-06-20 DOI: 10.4310/jdg/1668186787
Wentao Cao, L. Sz'ekelyhidi
We obtain global extensions of the celebrated Nash-Kuiper theorem for $C^{1,theta}$ isometric immersions of compact manifolds with optimal Holder exponent. In particular for the Weyl problem of isometrically embedding a convex compact surface in 3-space, we show that the Nash-Kuiper non-rigidity prevails upto exponent $theta<1/5$. This extends previous results on embedding 2-discs as well as higher dimensional analogues.
我们得到了具有最优Holder指数的紧致流形的$C^{1,θ}$等距浸入的著名Nash-Kuiper定理的全局扩展。特别是对于在3空间中等距嵌入凸紧致表面的Weyl问题,我们证明了Nash-Kuiper非刚性在指数$theta<1/5$之前占主导地位。这扩展了先前关于嵌入2-二元以及更高维类似物的结果。
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引用次数: 8
Rigidity of pairs of rational homogeneous spaces of Picard number $1$ and analytic continuation of geometric substructures on uniruled projective manifolds 无规射影流形上Picard数$1的有理齐次空间对的刚性及几何子结构的解析延拓
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-06-01 DOI: 10.4310/JDG/1559786425
N. Mok, Yunxin Zhang
Building on the geometric theory of uniruled projective manifolds by Hwang-Mok, which relies on the study of varieties of minimal rational tangents (VMRTs) from both the algebro-geometric and the differential-geometric perspectives, Mok, Hong-Mok and Hong-Park have studied standard embeddings between rational homogeneous spaces X = G/P of Picard number 1. Denoting by S ⊂ X an arbitrary germ of complex submanifold which inherits from X a geometric structure defined by taking intersections of VMRTs with tangent subspaces and modeled on some rational homogeneous space X0 = G0/P0 of Picard number 1 embedded in X = G/P as a linear section through a standard embedding, we say that (X0, X) is rigid if there always exists some γ ∈ Aut(X) such that S is an open subset of γ(X0). We prove that a pair (X0, X) of sub-diagram type is rigid whenever X0 is nonlinear, which in the Hermitian symmetric case recovers Schubert rigidity for nonlinear smooth Schubert cycles, and which in the general rational homogeneous case goes beyond earlier works dealing with images of holomorphic maps. Our methods apply to uniruled projective manifolds (X,K), for which we introduce a general notion of sub-VMRT structures π : C (S) → S, proving that they are rationally saturated under an auxiliary condition on the intersection C (S) := C (X) ∩ PT (S) and a nondegeneracy condition for substructures expressed in terms of second fundamental forms on VMRTs. Under the additional hypothesis that minimal rational curves are of degree 1 and that distributions spanned by sub-VMRTs are bracket generating, we prove that S extends to a subvariety Z ⊂ X. For its proof, starting with a “Thickening Lemma ” which yields smooth collars around certain standard rational curves, we show that the germ of submanifold (S;x0) and hence the associated germ of sub-VMRT structure on (S;x0) can be propagated along chains of “thickening ” curves issuing from x0, and construct by analytic continuation a projective family of chains of rational curves compactifying the latter family, thereby constructing the projective completion Z of S as its image under
基于Hwang-Mok的无规射影流形的几何理论,该理论依赖于从代数几何和微分几何角度对极小有理切线(VMRTs)的变化的研究,Mok、Hong-Mok和Hong-Park研究了Picard数1的有理齐次空间X = G/P之间的标准嵌入。用S∧X表示一个复子流形的任意子形,它从X继承了一个几何结构,该几何结构是由vmrt与切子空间的相交定义的,并通过标准嵌入在X = G/P中的Picard数1的有理齐次空间X0 = G0/P0上建模为线性截面,如果总存在某些γ∈Aut(X)使得S是γ(X0)的开子集,则我们说(X0, X)是刚性的。我们证明了子图型对(X0, X)在X0为非线性时是刚性的,它在厄米对称情况下恢复了非线性光滑舒伯特循环的舒伯特刚性,并且在一般理性齐次情况下超越了先前处理全纯映射像的工作。我们的方法应用于无规投影流形(X,K),为此我们引入了子vmrt结构π: C (S)→S的一般概念,证明了它们在相交C (S):= C (X)∩PT (S)的辅助条件下是合理饱和的,并证明了在vmrt上用第二基本形式表示的子结构的非简并性条件。在最小有理曲线为1次且由子vmrt张成的分布为夹角生成的附加假设下,我们证明S扩展到子变种Z∧x。为了证明它,我们从在某些标准有理曲线周围产生光滑项圈的“增厚引理”出发,证明子流形(S;x0)的子嗣以及(S;x0)上的子vmrt结构的相关子嗣可以沿着由x0发出的“增厚”曲线链传播。并通过解析延拓构造紧化后一族的有理曲线链的射影族,从而构造S的射影补全Z作为其像
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引用次数: 12
Band width estimates via the Dirac operator 通过Dirac算子估计带宽
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-05-21 DOI: 10.4310/jdg/1668186790
Rudolf Zeidler
Let $M$ be a closed connected spin manifold such that its spinor Dirac operator has non-vanishing (Rosenberg) index. We prove that for any Riemannian metric on $V = M times [-1,1]$ with scalar curvature bounded below by $sigma > 0$, the distance between the boundary components of $V$ is at most $C_n/sqrt{sigma}$, where $C_n = sqrt{(n-1)/{n}} cdot C$ with $C < 8(1+sqrt{2})$ being a universal constant. This verifies a conjecture of Gromov for such manifolds. In particular, our result applies to all high-dimensional closed simply connected manifolds $M$ which do not admit a metric of positive scalar curvature. We also establish a quadratic decay estimate for the scalar curvature of complete metrics on manifolds, such as $M times mathbb{R}^2$, which contain $M$ as a codimension two submanifold in a suitable way. Furthermore, we introduce the "$mathcal{KO}$-width" of a closed manifold and deduce that infinite $mathcal{KO}$-width is an obstruction to positive scalar curvature.
设$M$是闭连通的自旋流形,使其旋量Dirac算子具有不消失(Rosenberg)指数。我们证明了对于$V=Mtimes[-1,1]$上的任何黎曼度量,其标量曲率以$sigma>0$为界,$V$的边界分量之间的距离至多为$C_n/sqrt{sigma}$,其中$C_n=sqrt{(n-1)/{n}}cdot C$,$C<8(1+sqrt{2})$是通用常数。这验证了Gromov对这类流形的一个猜想。特别地,我们的结果适用于所有不允许正标量曲率度量的高维闭单连通流形$M$。我们还建立了完备度量在流形上的标量曲率的二次衰变估计,如$Mtimesmathb{R}^2$,它以适当的方式包含$M$作为余维二个子流形。此外,我们引入了闭流形的“$mathcal{KO}$-width”,并推导出无穷大的$mathcal{KO}$-width是正标量曲率的障碍。
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引用次数: 25
Homogenization of random quasiconformal mappings and random Delauney triangulations 随机拟共形映射的同构与随机Delauney三角剖分
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-05-20 DOI: 10.4310/jdg/1689262063
O. Ivrii, V. Marković
In this paper, we solve two problems dealing with the homogenization of random media. We show that a random quasiconformal mapping is close to an affine mapping, while a circle packing of a random Delauney triangulation is close to a conformal map, confirming a conjecture of Stephenson. We also show that on a Riemann surface equipped with a conformal metric, a random Delauney triangulation is close to being circle packed.
在本文中,我们解决了处理随机介质均匀化的两个问题。我们证明了随机拟共形映射接近仿射映射,而随机Delauney三角剖分的圆填充接近共形映射,证实了Stephenson的一个猜想。我们还证明了在具有保角度量的黎曼曲面上,随机Delauney三角剖分接近于圆填充。
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引用次数: 1
On O’Hara knot energies I: Regularity for critical knots 论O 'Hara结能I:临界结的规律性
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-05-15 DOI: 10.4310/jdg/1664378616
S. Blatt, P. Reiter, A. Schikorra
We develop a regularity theory for extremal knots of scale invariant knot energies defined by J. O'hara in 1991. This class contains as a special case the Mobius energy. For the Mobius energy, due to the celebrated work of Freedman, He, and Wang, we have a relatively good understanding. Their approch is crucially based on the invariance of the Mobius energy under Mobius transforms, which fails for all the other O'hara energies. We overcome this difficulty by re-interpreting the scale invariant O'hara knot energies as a nonlinear, nonlocal $L^p$-energy acting on the unit tangent of the knot parametrization. This allows us to draw a connection to the theory of (fractional) harmonic maps into spheres. Using this connection we are able to adapt the regularity theory for degenerate fractional harmonic maps in the critical dimension to prove regularity for minimizers and critical knots of the scale-invariant O'hara knot energies.
我们发展了J. O'hara(1991)定义的尺度不变结能量的极限结的正则性理论。这个类包含了一个特殊的莫比乌斯能量。对于莫比乌斯能量,由于Freedman, He和Wang的著名工作,我们有一个比较好的理解。他们的方法关键是基于莫比乌斯变换下莫比乌斯能量的不变性,这对于所有其他的奥哈拉能量来说都是失败的。我们通过将尺度不变的O'hara结能量重新解释为作用于结参数化的单位切线上的非线性、非局部的L^p -能量来克服这一困难。这使我们能够与球的(分数)调和映射理论建立联系。利用这一联系,我们能够将临界维上退化分数阶调和映射的正则性理论应用于证明标度不变O'hara结能量的极小值和临界结的正则性。
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引用次数: 8
On the Index of Willmore spheres 关于Willmore球的指数
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-05-10 DOI: 10.4310/jdg/1685121319
J. Hirsch, E. Mader-Baumdicker
We consider unbranched Willmore surfaces in the Euclidean space that arise as inverted complete minimal surfaces with embedded planar ends. Several statements are proven about upper and lower bounds on the Morse Index - the number of linearly independent variational directions that locally decrease the Willmore energy. We in particular compute the Index of a Willmore sphere in the three-space. This Index is $m-d$, where $m$ is the number of ends of the corresponding complete minimal surface and $d$ is the dimension of the span of the normals at the $m$-fold point. The dimension $d$ is either two or three. For $m=4$ we prove that $d=3$. In general, we show that there is a strong connection of the Morse Index to the number of logarithmically growing Jacobi fields on the corresponding minimal surface.
我们考虑欧几里得空间中的无分支Willmore曲面,这些曲面是具有嵌入平面末端的反向完全极小曲面。关于Morse指数的上界和下界,已经证明了几种说法。Morse指数是局部降低Willmore能量的线性独立变分方向的数量。我们特别计算了Willmore球体在三个空间中的指数。该索引为$m-d$,其中$m$是相应完整最小曲面的末端数量,$d$是$m$折叠点处法线跨度的维度。维度$d$是两个或三个。对于$m=4$,我们证明$d=3$。通常,我们证明了Morse指数与相应最小曲面上对数增长的Jacobi场的数量之间存在强联系。
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引用次数: 3
Generalized square knots and homotopy $4$-spheres 广义方结与同伦球
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-04-17 DOI: 10.4310/jdg/1668186788
J. Meier, Alexander Zupan
The purpose of this paper is to study geometrically simply-connected homotopy 4-spheres by analyzing $n$-component links with a Dehn surgery realizing $#^n(S^1times S^2)$. We call such links $n$R-links. Our main result is that a homotopy 4-sphere that can be built without 1-handles and with only two 2-handles is diffeomorphic to the standard 4-sphere in the special case that one of the 2-handles is attached along a knot of the form $Q_{p,q} = T_{p,q}#T_{-p,q}$, which we call a generalized square knot. This theorem subsumes prior results of Akbulut and Gompf. Along the way, we use thin position techniques from Heegaard theory to give a characterization of 2R-links in which one component is a fibered knot, showing that the second component can be converted via trivial handle additions and handleslides to a derivative link contained in the fiber surface. We invoke a theorem of Casson and Gordon and the Equivariant Loop Theorem to classify handlebody-extensions for the closed monodromy of a generalized square knot $Q_{p,q}$. As a consequence, we produce large families, for all even $n$, of $n$R-links that are potential counterexamples to the Generalized Property R Conjecture. We also obtain related classification statements for fibered, homotopy-ribbon disks bounded by generalized square knots.
本文的目的是通过分析$n$-分量链接来研究几何简单连通的同伦球,并用Dehn运算实现$^n(S^1times S^2)$。我们称这种链接为$n$R-links。我们的主要结果是,在一个2-句柄沿着形式为$Q_{p,Q}=T_{p,Q}#T_{-p,Q}$的结(我们称之为广义方结)连接的特殊情况下,一个可以在没有1-句柄且只有两个2-句柄的情况下建立的同伦图4-球体与标准4-球体是微分同胚的。这个定理包含了Akbulut和Gompf的先前结果。在此过程中,我们使用Heegaard理论中的薄位置技术对2R链路进行了表征,其中一个组件是纤维结,表明第二个组件可以通过简单的手柄添加和手柄侧面转换为包含在纤维表面中的衍生链路。我们引用Casson和Gordon的一个定理以及等变环定理对广义方结$Q_{p,Q}$的闭单调的可处理体扩张进行分类。因此,我们产生了$n$R-link的大族,甚至对于所有$n$,它们是广义性质R猜想的潜在反例。我们还得到了由广义方结约束的纤维、同伦带圆盘的相关分类声明。
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引用次数: 10
Scherk-like translators for mean curvature flow 平均曲率流的Scherk-like翻译器
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-03-11 DOI: 10.4310/jdg/1675712995
D. Hoffman, F. Mart'in, B. White
We prove existence and uniqueness for a two-parameter family of translators for mean curvature flow. We get additional examples by taking limits at the boundary of the parameter space. Some of the translators resemble well-known minimal surfaces (Scherk's doubly periodic minimal surfaces, helicoids), but others have no minimal surface analogs.
我们证明了平均曲率流的一个双参数翻译器族的存在性和唯一性。通过在参数空间的边界上取极限,我们得到了更多的例子。一些翻译者类似于众所周知的极小曲面(Scherk的双周期极小曲面,螺旋曲面),但其他翻译者没有极小曲面的类似物。
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引用次数: 22
Kohn–Rossi cohomology and nonexistence of CR morphisms between compact strongly pseudoconvex CR manifolds 紧强伪凸CR流形间的Kohn-Rossi上同调及CR态射的不存在性
IF 2.5 1区 数学 Q1 Mathematics Pub Date : 2019-03-01 DOI: 10.4310/JDG/1552442610
S. Yau, Huaiqing Zuo
One of the fundamental questions in CR geometry is: Given two strongly pseudoconvex CR manifolds X1 and X2 of dimension 2n−1, is there a non-constant CR morphism between them? In this paper, we use Kohn-Rossi cohomology to show the non-existence of non-constant CR morphism between such two CR manifolds. Specifically, if dimH KR(X1) < dimH p,q KR(X2) for any (p, q) with 1 ≤ q ≤ n− 2, then there is no non-constant CR morphism from X1 to X2.
CR几何中的一个基本问题是:给定两个维数为2n−1的强伪凸CR流形X1和X2,它们之间是否存在非常CR态射?本文利用Kohn-Rosi上同调证明了这两个CR流形之间的非常CR态射的不存在性。特别地,如果对于1≤q≤n−2的任何(p,q),dimH-KR(X1)
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引用次数: 1
期刊
Journal of Differential Geometry
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