We classify simply connected compact Sasaki manifolds of dimension $2n+1$ with positive transverse bisectional curvature. In particular, the Kähler cone corresponding to such manifolds must be bi-holomorphic to $\C^{n+1}\backslash \{0\}$. As an application we recover the Mori-Siu-Yau theorem on the Frankel conjecture and extend it to certain orbifold version. The main idea is to deform such Sasaki manifolds to the standard round sphere in two steps, both fixing the complex structure on the Kähler cone. First, we deform the metric along the Sasaki-Ricci flow and obtain a limit Sasaki-Ricci soliton with positive transverse bisectional curvature. Then by varying the Reeb vector field along the negative gradient of the volume functional, we deform the Sasaki-Ricci soliton to a Sasaki-Einstein metric with positive transverse bisectional curvature, i.e. a round sphere. The second deformation is only possible when one treats simultaneously regular and irregular Sasaki manifolds, even if the manifold one starts with is regular(quasi-regular), i.e. Kähler manifolds(orbifolds).
We introduce a weaker notion of generic submanifold of a Sasakian manifold and we prove a Frankel type theorem for this kind of submanifolds under suitable hypotesis on the index of the scalar Levi forms determined by normal directions. It concerns the intersection between a generic and an invariant submanifold and the intersection between two generic submanifolds. From this theorem we derive some topological information about generic submanifolds of Sasakian space forms.
On the Hamilton-Tian Conjecture in a compact transverse Fano Sasakian $5$-manifold
Shanghai Institute of Mathematics and Interdisciplinary Sciences(上海数学与交叉学科研究院);School of Mathematics and Statistics, Xinyang Normal University(信阳师范大学数学与统计学院);Department of Mathematics, National Taiwan Normal University(台湾师范大学数学系);Department of Applied Mathematics, National Pingtung University(国立屏东大学应用数学系)
On the Sasakian Structure of Manifolds with Nonnegative Transverse Bisectional Curvature
Shanghai Institute of Mathematics and Interdisciplinary Sciences(上海数学与交叉学科研究院);School of Mathematics and Statistics, Xinyang Normal University(信阳师范大学数学与统计学院);Department of Mathematics, National Taiwan Normal University(台湾师范大学数学系);Department of Applied Mathematics, National Pingtung University(屏东科技大学应用数学系)
On Compact Hermitian Surfaces With Positive Strominger-Bismut Sectional Curvature
Halıcıoğlu Data Science Institute, University of California San Diego(加州大学圣地亚哥分校);Yau Mathematical Sciences Center, Tsinghua University(清华大学);School of Mathematical Sciences, Chongqing Normal University(重庆师范大学)
This is largely an exposition article that expands the author's talk at the Xiamen International Conference on Geometric Analysis in June 2021. We first survey the author's joint work with Jiyuan Han on the Yau-Tian-Donaldson (YTD) conjecture for $g$-weighted Kähler-Ricci solitons ($g$-solitons). We then review recent works of Apostolov-Canderbank-Jubert-Lahdili which establish a connection between a particular $g$-soliton equation with Ricci-flat Kähler cone metrics (or equivalently Sasaki-Einstein metrics). The main interest in this connection is the transformation of a possibly irregular Sa…
Lichnerowicz猜想断言所有的调和流形要么是平坦的要么是秩为1的局部对称空间。这个猜想已被Z. Szabó \cite{Sz}:具有紧万有覆盖的调和流形. E. Damek和F.利玛窦\cite{DR}提供的例子表明,在非紧的情况下,猜想是错误的。然而,这样的流形不允许紧商。本文利用秩的概念研究了单连通非平坦非紧调和流形$X$上的渐近几何和测地流。在本文的第一部分中,我们证明了以下断言是等价的。体积的增长是纯指数的,$X$的秩是1,测地流是Anosov关于Sasaki度量,$X$是Gromov双曲。本文第二部分证明了若$X$是一个无焦点的非平坦调和流形,则测地流是Anosov流。在证明的过程中,我们得到了任意黎曼流形上的某些部分双曲流是Anosov流,这是调和流形以外的有趣的。结合\cite{BCG},\cite{BFL}和\cite{FL}的刚性定理,我们对所有无焦点或含Gromov双曲基本群的紧致调和流形证实了Lichnerowicz猜想.
Fatness and positive curvatures on Riemannian submersions
Institute of Mathematics and Informatics, Bulgarian Academy of Sciences(保加利亚科学院数学与信息学研究所);College of Arts and Sciences, Department of Mathematics, University of Miami(迈阿密大学文理学院数学系);Instituto de Matemática, Estatística e Computação Científica (IMECC) da Universidade Estadual de Campinas (Unicamp)(坎皮纳斯州立大学数学、统计与科学计算研究所(IMECC));ICT - Unifesp(圣保罗联邦理工学院)